chemistry study notes

8/3/2019 Chemistry Study Notes

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accuracy

a description of how close a measurement is to the true value of the

quantity measured

actinide

any of the elements of the actinide series, which have atomic

numbers from 89 (actinium, Ac) through 103 (lawrencium, Lr)

alkali metalone of the elements of Group 1 of the periodic table (lithium,sodium, potassium, rubidium, cesium, and francium)

alkaline-earth

metal

one of the elements of Group 2 of the periodic table (beryllium,

magnesium, calcium, strontium, barium, and radium)

alloy a solid or liquid mixture of two or more metals

anion an ion that has a negative charge

Atom

the smallest unit of an element that maintains the properties of that

element

atomic mass the mass of an atom expressed in atomic mass units

Atomic number

the number of protons in the nucleus of an atom; the atomic number

is the same for all atoms of an element

aufbau principle

the principle that states that the structure of each successive element

is obtained by adding one proton to the nucleus of the atom and one

electron to the lowest-energy orbital that is available

Avogadros

number 6.022 1023, the number of atoms or molecules in 1 mol

bond energy

the energy required to break the bonds in 1 mol of a chemical

compound

bond length

the distance between two bonded atoms at their minimum potential

energy; the average distance between the nuclei of two bonded atoms

bond radiuscenter of two like atoms that arehalf the distance from center to bonded together

cation an ion that has a positive charge

Chemical Any substance that has a defined composition

Chemical change

a change that occurs when one or more substances change into

entirely new substances with different properties

Chemical property

p property of matter that describe a substances ability to participate

in chemical reactions

Chemical Reaction

The process by which one or more substances change to produce one

or more different substances

Compounda substance made up of atoms of two or more different elementsoined by chemical bonds.

Conversion factor

a ratio that is derived from the quality of two different units and that

can be used to convert from one unit to the other

covalent bond a bond formed when atoms share one or more pairs of electrons

crystal lattice the regular pattern in which a crystal is arranged

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Density

the ratio of the mass of a substance to the volume of the substance

D=M/V

dipole

that contains both positively and

a molecule or part of a molecule negatively charged regions

double bond a covalent bond in which two atoms share two pairs of electrons

electromagnetic

spectrum all of the frequencies or wavelengths of electromagnetic radiation

Electron a subatomic particle that has a negative electric charge

electron

configuration the arrangement of electrons in an atom

electron shielding

the reduction of the attractive force between a positively charged

nucleus and its outermost electrons due to the cancellation of some

of the positive charge by the negative charges of the inner electrons

electronegativity

a measure of the ability of an atom in a chemical compound to attract

electrons

Elementa substance that cannot be separated or broken down into simplersubstances by chemical means

Endothermic descries a process in which heat is absorbed from the environment

Energy the capacity to do work

Evaporation the change of a substance from a liquid to a gas

excited state

a state in which an atom has more energy than it does at its ground

state

Exothermic

describes a process in which a system releases heat into the

environment

ground state the lowest energy state of a quantized system

groupa vertical column of elements in the periodic table; elements in agroup share chemical properties

halogen

one of the elements of Group 17 of the periodic table (fluorine,

chlorine, bromine, iodine, and astatine); halogens combine with most

metals to form salts

Heat

the energy transferred between objects that are at different

temperatures

Heterogeneous composed of dissimilar components

Homogeneous

describes something that has a uniform structure or composition

throughout

Hunds rule

the rule that states that for an atom in the ground state, the number ofunpaired electrons is the maximum possible and these unpaired

electrons have the same spin

Hypothesis

a theory or explanation that is based on observations and that can be

tested

ion

an atom, radical, or molecule that has gained or lost one or more

electrons and has a negative or positive charge

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ionization energy the energy required to remove an electron from an atom or ion

isotope

an atom that has the same number of protons (atomic number) as

other atoms of the same element but has a different number of

neutrons(atomic mass)

Kinetic energy the energy of an object that is due to the objects motion

lanthanide

a member of the rare-earth series of elements, whose atomic

numbers range from 58 (cerium) to 71 (lutetium)

lattice energy

the energy associated with constructing a crystal lattice relative to

the energy of all constituent atoms separated by infinite distances

Law a summary of many experimental results and observations

Law of

conservation of

energy

the law that states that energy cannot be created or destroyed but can

be changed from on form to another

Law of

conservation of

mass

the law that states that mass cannot be created or destroyed in

ordinary chemical and physical changeslaw of

conservation of

mass

the law that states that mass cannot be created or destroyed in

ordinary chemical and physical changes

law of definite

proportions

the law states that a chemical compound always contains the same

elements in exactly the same proportions by weight or mass

law of multiple

proportions

the law that states that when two elements combine to form two or

more compounds, the mass of one element that combines with a

given mass of the other is in the ratio of small whole numbers

Lewis structure

a structural formula in which electrons are represented by dots; dot

pairs or dashes between two atomic symbols represent pairs incovalent bonds

main-group

element an element in the s-block or p-block of the periodic table

Mass a measure of the amount of matter in an object

Mass number

the sum of the numbers of protons and neutrons of the nucleus of an

atom

Matter anything that has mass and takes up space

Mixture

a combination of two or more substances that are not chemically

combined

molar mass the mass in grams of 1 mol of a substance

mole

the SI base unit used to measure the amount of a substance whose

number of particles is the same as the number of atoms in 12 g of

carbon-12

molecular orbital

the region of high probability that is occupied by an individual

electron as it travels with a wavelike motion in the three-

dimensional space around one of two or more associated nuclei

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Molecule

the smallest unit of substance that keeps all of the physical and

chemical properties of that substance

Neutron

a subatomic particle that has no charge and that is found in the

nucleus of an atom

noble gas

an unreactive element of Group 18 of the periodic table (helium,

neon, argon, krypton, xenon, or radon) that has eight electrons in itsouter level (except for helium, which has two electrons)

nonpolar covalent

bond

a covalent bond in which the bonding electrons are equally attracted

to both bonded atoms

nuclear reaction a reaction that affects the nucleus of an atom

Nucleus an atoms central region, which is made up of protons and neutrons

octet rule

a concept of chemical bonding theory that is based on the

assumption that atoms tend to have either empty valence shells or

full valence shells of eight electrons

orbital

a region in an atom where there is a high probability of finding

electronsPauli exclusion

principle

the principle that states that two particles of a certain class cannot be

in the exact same energy state

period a horizontal row of elements in the periodic table

periodic law

the law that states that the repeating physical and chemical properties

of elements change periodically with their atomic number

Physical change

a change of matter from one form to another without a change in

chemical properties

Physical property

a characteristic of a substance that does not involve a chemical

change, such as density, color, or hardness

polar covalentbond

a covalent bond in which a shared pair of electrons is held moreclosely by one of the atoms

polyatomic ion an ion made of two or more atoms

precision the exactness of a measurement

Product A substance that forms in a chemical reaction

Proton

a subatomic particle that has a positive charge and that is found in

the nucleus of an atom; the number of protons of the nucleus is the

atomic number, which determines the identity of an element

Pure Substance

a sample of matter, either a single element or a single compound,

that has definite chemical and physical properties

Quantity something that has magnitude, size, or amount

quantum number a number that specifies the properties of electrons

Reactant A substance or molecule that participates in a chemical reaction

resonance

structure

in chemistry, any one of two or more possible configurations of the

same compound that have identical geometry but different

arrangements of electrons

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salt

an ionic compound that forms when a metal atom or a positive

radical replaces the hydrogen of an acid

Scientific method

a series of step followed to solve problems, including collecting data,

formulating a hypothesis, testing the hypothesis, and stating

conclusions

significant figurea prescribed decimal place that determines the amount of roundingoff to be done based on the precision of the measurement

single bond a covalent bond in which two atoms share one pair of electrons

Specific heat

the quantity of heat required to raise a unit mass of homogeneous

material 1 K or 1 Celsius in a specified way given constant pressure

and volume

States of matter The physical forms of matter, which are solid, liquid, gas and plasma

superheavy

element an element whose atomic number is greater than 106

Temperature a measure of how hot (or col) something is

Theoryan explanation for some phenomenon that is based n observation,experimentation and reasoning

transition metal

one of the metals that can use the inner shell before using the outer

shell to bond

triple bond a covalent bond in which two atoms share three pairs of electrons

Unit a quantity adopted as a standard of measurement

unit cell

the smallest portion of a crystal lattice that shows the three-

dimensional pattern of the entire lattice

unshared pair

a nonbonding pair of electrons in the valence shell of an atom; also

called lone pair

valence electronan electron that is found in the outermost shell of an atom and thatdetermines the atoms chemical properties

valence electron

an electron that is found in the outermost shell of an atom and that

determines the atoms chemical properties

Volume a measure of the size of a body or region n three-dimensional space.

VSEPR theory

a theory that predicts some molecular shapes based on the idea that

pairs of valence electrons surrounding an atom repel each other

Weight a measure of gravitational force exerted on an object

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Chapter 1 Highlights:

SECTION ONE! What Is Chemistry? Chemistry is the study of chemicals, their properties, and the reactions in which

they are involved.

Three of the states of matter are solid, liquid, and gas.

Matter undergoes both physical changes and chemical changes. Evidence can help to identify the

type of change.

SECTION TWO ! Describing Matter Matter has both mass and volume; matter thus has density, which is the ratio

of mass to volume.

Mass and weight are not the same thing. Mass is a measure of the amount of matter in an object.

Weight is a measure of the gravitational force exerted on an object.

SI units are used in science to express quantities. Derived units are combina- tions of the basic SI

units.

Conversion factors are used to change a given quantity from one unit to another unit.

Properties of matter may be either physical or chemical.

SECTION THREE! How Is Matter Classified? All matter is made from atoms.

All atoms of an element are alike.

Elements may exist as single atoms or as molecules.

A molecule usually consists of two or more atoms combined in a definite ratio.

Matter can be classified as a pure substance or a mixture.

Elements and compounds are pure substances. Mixtures may be homogeneous or heterogeneous.


SECTION ONE! Energy

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SECTION ONE! Substances Are Made of Atoms Three laws support the existence of atoms: the law of definite proportions, the

law of conservation of mass, and the law of multiple proportions.

Daltons atomic theory contains five basic principles, some of which have been modified.

SECTION TWO ! Structure of Atoms Protons, particles that have a positive charge, and neutrons, particles that have a

neutral charge, make up the nuclei of most atoms.

Electrons, particles that have a negative charge and very little mass, occupy the region around the

nucleus.

The atomic number of an atom is the number of protons the atom has. The mass number of an atom

is the number of protons plus the number of neutrons.

Isotopes are atoms that have the same number of protons but different numbers of neutrons.

SECTION THREE! Electron Configuration The quantum model describes the probability of locating an electron at any place.

Each electron is assigned four quantum numbers that describe it. No two electrons of an atom can

have the same four quantum numbers.

The electron configuration of an atom reveals the number of electrons an atom has.

SECTION FOUR!! Counting Atoms The masses of atoms are expressed in atomic mass units (amu). The mass of an

atom of the carbon-12 isotope is defined as exactly 12 atomic mass units.

The mole is the SI unit for the amount of a substance that contains as many particles as there are

atoms in exactly 12 grams of carbon-12.

Avogadros number, 6.022 1023 particles per mole, is the number of particles in a mole.Chapter 4 Highlights:

SECTION ONE! How Are Elements Organized?

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John Newlands, Dmitri Mendeleev, and Henry Moseley contributed to the

development of the periodic table.

The periodic law states that the properties of elements are periodic functions of the elements atomic

numbers.

In the periodic table, elements are ordered by increasing atomic number. Rows are called periods.

Columns are called groups.

Elements in the same period have the same number of occupied energy levels. Elements in the same

group have the same number of valence electrons.

SECTION TWO ! Tour of the Periodic Table The main-group elements are Group 1 (alkali metals), Group 2 (alkaline-earth

metals), Groups 1316, Group 17 (halogens), and Group 18 (noble gases).

Hydrogen is in a class by itself.

Most elements are metals, which conduct electricity. Metals are also ductile and malleable.

Transition metals, including the lanthanides and actinides, occupy the center of the periodic table.

SECTION THREE! Trends in the Periodic Table Periodic trends are related to the atomic structure of the elements.

Ionization energy, electronegativity, and electron affinity generally increase as you move across a

period and decrease as you move down a group.

Atomic radius and ionic size generally decrease as you move across a period and increase as you

move down a group.

Melting points and boiling points pass through two cycles of increasing, peaking, and then

decreasing as you move across a period.

SECTION FOUR!! Where Did the Elements Come From? The 93 natural elements were formed in the interiors of stars. Synthetic elements (elements whose

atomic numbers are greater than 93) are made using particle accelerators.

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A transmutation is a nuclear reaction in which one nucleus is changed into another nucleus.


SECTION ONE! Simple Ions Atoms may gain or lose electrons to achieve an electron configuration identical

to that of a noble gas.

Alkali metals and halogens are very reactive when donating and accepting electrons from one

another.

Electrons in the outermost energy level are known as valence electrons.

Ions are electrically charged particles that have different chemical properties than their parent atoms.

SECTION TWO ! Ionic Bonding and Salts The opposite charges of cations and anions attract to form a tightly packed

substance of bonded ions called a crystal lattice.

Salts have high melting and boiling points and do not conduct electric current in the solid state, but

they do conduct electric current when melted or when dissolved in water.

Salts are made of unit cells that have an ordered packing arrangement.

SECTION THREE! Names and Formulas of Ionic Compounds Ionic compounds are named by joining the cation and anion names.

Formulas for ionic compounds are written to show their balance of overall charge.

A polyatomic ion is a group of two or more atoms bonded together that functions as a single unit.

Parentheses are used to group polyatomic ions in a chemical formula with a subscript.


SECTION ONE! Covalent Bonds Covalent bonds form when atoms share pairs of electrons.

Atoms have less potential energy and more stability after they form a covalent bond.

The greater the electronegativity difference, the greater the polarity of the bond.

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The physical and chemical properties of a compound are related to the compounds bond type.

SECTION TWO ! Drawing and Naming Molecules In a Lewis structure, the elements symbol represents the atoms nucleus and

inner-shell electrons, and dots represent the atoms valence electrons.

Two atoms form single, double, and triple bonds depending on the number of electron pairs that the

atoms share.

Some molecules have more than one valid Lewis structure. These structures are called resonance

structures.

Molecular compounds are named using the elements names, a system of prefixes, and -ide as the

ending for the second element in the compound.

SECTION THREE! Molecular Shapes VSEPR theory states that electron pairs in the valence shell stay as far

apart as possible.

VSEPR theory can be used to predict the shape of a molecule.

Molecular shapes predicted by VSEPR theory include linear, bent, trigonal planar, tetrahedral, and

trigonal pyramidal.

The shape of a molecule affects the molecules physical and chemical properties.

Chemistry Final Exam Term 1 Review Sheet

Three stats of matter: What they are and how to change between them

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Gas

Liquid

Solid

FreezingMelting

Evaporation Condensation


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Reactants and Products

Observations of a chemical/physical change

Volume, Mass, Weight and density calculations

Chemical and physical properties and changes

Mixtures vs. Compounds

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A+B C+D A + B = Reactants = A substance or molecule thatparticipates in a chemical reaction

C+ D = Products = A substance that forms in achemical reaction

- ChemicalChange

ColorChange

Precepitate

Heat

Gas

Reactions

- PhysicalChange

Dissolve NoReactions

D=M/V D=Denisity

M=Mass

V=Volume

Difference between mass and weight:

Mass : a measure of the amount of matter in an object

Weight : a measure of gravitational force exerted on anobject

Chemical Change : a change that occurs when one or moresubstances change into entirely new substances with differentproperties

Physical Change : a change of matter from one form to anotherwithout a change in chemical properties

PhysicalProperty-observebydensity

Mixture:Nobonding,NoReaction

TwoTypeofMixture:

- Hemomgenous:Dissolve

- Hetrogenous:DontDissolve

Compound:reaction,Chemicalbond


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Specific Heat Calculations

Scientific Method

Significant Figures

13

C=speci3icheatatagivenpressure

q=energytransferredasheat

m=mass

DeltaT=representsthedifferencebetweenthe

intialand3inaltempreatures

Unti:J/g*K

Nonzero digits are always significant.

For example, 46.3 m has three significant figures.

For example, 6.295 g has four significant figures.

Zeros between nonzero digits are significant.

For example, 40.7 L has three significant

figures.

For example, 87 009 km has five significant figures.

Zeros in front of nonzero digits are not significant.

For example, 0.0095 87 m has four significant figures.

For example, 0.0009 kg has one significant figure.

Zeros both at the end of a number and to the right of a decimal point are significant.

For example, 85.00 g has four significant

figures.

For example, 9.070 000 000 cm has 10 significant figures.

Zeros both at the end of a number but to the left of a decimal point may not be significant. If a zero

has not been measured or estimated, it is not significant. A decimal point placed after zeros indicates

that the zeros are significant.

For example, 2000 m may contain from one to four significant figures, depending on how many zeros areplaceholders. For values given in this book, assume that 2000 m has one significant figure.


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Law of Conservation of Mass

Law of Conservation of Energy

Ground stats and Excited State

Electron Configuration

Quantum Numbers

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the law that states that mass cannot be created or destroyed in ordinarychemical and physical changes

ener can not be create or destro but it ust chan e to a di erent state

Normally, if an electron is in a state of lowest possible energy, it is in a ground

state. If an electron gains energy, it moves to an excited state. An electron in

an excited state will release a specific quantity of energy as it quickly falls

back to its ground state. This energy is emitted as certain wavelengths of light,

which give each element a unique line-emission spectrum.

S:2

P:6D:10

F14

a number that specifies the properties of electrons

Pressheretoseethevideo.
http://www.youtube.com/watch?v=VfBcfYR1VQo&feature=relatedhttp://www.youtube.com/watch?v=VfBcfYR1VQo&feature=related


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Pauli Exclusion Principle, Aufbau Principle, Hunds rules, Octet Rule

Atoms- Protons, Neutrons, Electrons, Proton Number

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Pauli Exlusion- States that two particles of a certain class cannot be

in the exact same energy state- Every electron have the be unique

Aufbau Principle- states that the structure of each successive element is

obtained by adding one proton to the nucleus of theatom and one electron to the lowest-energy orbital thatis available

- lowest energy orbitals filled first

Hunds Principle- states that for an atom in the ground state, the number of unpaired

electrons is the maximum possible and these unpaired electrons have thesame spin

Octet Rule- Atom have 8 valence electron

Formoreinformationaboutvalenceelectronandoctetrulepresshere

Proton : a subatomic particle that has a positive charge and that isfound in the nucleus of an atom; the number of protons of the nucleusis the atomic number, which determines the identity of an element

Neutron: a subatomic particle that has no charge and that is found inthe nucleus of an atom

Electron: a subatomic particle that has a negative electric charge

Mass Number = (Number of Protons) + (Number of Neutrons)

The atomic number is the number of protons in an atom of an element.

Atoms must have equal numbers of protons and electrons.

Neutron for Kr = 84 = 36 + (Number of Neutrons)

Number of neutrons = Mass number minus Atomic number
http://en.wikipedia.org/wiki/Octet_rulehttp://en.wikipedia.org/wiki/Octet_rule


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Periodic Groups - Alkali Metals, Alkaline Earth Metals, Transition Metals, Halogens, Noble Gases,

Lanthanides, Actinides, Hydrogen

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Group 1: Alkali Metals

These elements are less dense than other metals, form ions with a +1 charge,

and have the largest atom sizes of elements in their periods. The alkali metalsare highly reactive.

Group 2: Alkaline Earth Metals

These metals form many compounds. They have ions with a +2 charge. Theiratoms are smaller than those of the alkali metals.

Groups 3-12: Transition Metals

These elements are very hard, with high melting points and boiling points. Thetransition metals are good electrical conductors and are very malleable. They form

positively charged ions.

Group 17: Halogens

These nonmetals form ions with a -1 charge. The physical properties of thehalogens vary. The halogens are highly reactive.

Group 18: Noble Gases

These elements are used to make lighted signs, refrigerants, and lasers. The noble gases are notreactive. This is because they have little tendency to gain or lose electrons.

Lanthanides

The lanthanides are silvery metals that tarnish easily. They are relatively soft metals, with high melting and boiling poin

The lanthanides react to form many different compounds. These elements are used in lamps, magnets, lasers, and to impthe properties of other metals.

Actinides

All of the actinides are radioactive, with positively charged ions. They are reactive metals that formcompounds with most nonmetals. The actinides are used in medicines and nuclear devices.

Hydrogen

Hydrogen has a single positive charge, like the alkali metals, but at

room temperature, it is a gas that doesn't act like a metal.Therefore, hydrogen usually is labeled as a nonmetal.


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Periodic Trends, Electronegativity, Electron Affinity, Atomic Radii, Ionization Energy

17

Electronegativity:

Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. Thehigher the electronegativity of an atom, the greater its attraction for bonding electrons. Electronegativity

is related to ionization energy. Electrons with low ionization energies have low electronegativitiesbecause their nuclei do not exert a strong attractive force on electrons. Elements with high ionizationenergies have high electronegativities due to the strong pull exerted on electrons by the nucleus. In agroup, the electronegativity decreases as atomic number increases, as a result of increased distance

between the valence electron and nucleus (greater atomic radius). An example of an electropositive (i.e.,low electronegativity) element is cesium; an example of a highly electronegative element is fluorine.

Electron Affinity

Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurswhen an electron is added to a gaseous atom. Atoms with stronger effective nuclear charge have greaterelectron affinity. Some generalizations can be made about the electron affinities of certain groups in the

periodic table. The Group IIA elements, the alkaline earths, have low electron affinity values. Theseelements are relatively stable because they have filleds subshells. Group VIIA elements, the halogens,have high electron affinities because the addition of an electron to an atom results in a completely filledshell. Group VIII elements, noble gases, have electron affinities near zero, since each atom possesses astable octet and will not accept an electron readily. Elements of other groups have low electron affinities.

Atomic Radii

The atomic radius of an element is half of the distance between the centers of two atoms of that elementthat are just touching each other. Generally, the atomic radius decreases across a period from left to rightand increases down a given group. The atoms with the largest atomic radii are located in Group I and atthe bottom of groups.


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Covalent Compounds, naming, formulas

19

a bond formed when atoms share one or more pairs of electrons

Covalent-Non-Metal+Non-Metal

VIDEO

Naming:

All covalent compounds have two word names. The first word typically corresponds to the first element in the formulaand the second corresponds to the second element in the formula except that "-ide" is substituted for the end. As a resultHF is named "hydrogen fluoride", because hydrogen is the first element and fluorine is the second element.

If there is more than one atom of an element in a molecule, we need to add prefixes to these words to tell us how manyare present. Here are the prefixes you'll need to remember:

Let's see how this works:

Examples:

P2O5 - this is named diphosphorus pentoxide, because there are two phosphorus atoms and five oxygen atoms.CO - this is carbon monoxide (you need the "mono-" because there's only one oxygen atom).CF4 - this is carbon tetrafluoride, because there's one carbon atom and four fluorine atoms.

1 Mono

2 Di-

3 Tri-

4 Tetra-

5 Penta-

6 Hexa-

7 Hepta-

8 Octa-

Properties of Covalent :

- Covalent compounds generally have much lower melting and boiling points than ionic compounds.

- Covalent compounds are soft and squishy (compared to ionic compounds)

- Covalent compounds tend to be more flammable than ionic compounds.

- Covalent compounds don't conduct electricity in water.

- Covalent compounds aren't usually very soluble in water.
http://www.youtube.com/watch?v=-Eh_0Dseg3E&feature=relatedhttp://www.youtube.com/watch?v=-Eh_0Dseg3E&feature=related


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Lewis Structure

Molecular Geometry

20

a structural formula in which electrons are represented bydots; dot pairs or dashes between two atomic symbolsrepresent pairs in covalent bonds

Video

1) The number of valence electrons is 16. (Carbon has fourelectrons, and each of the oxygens have six, for a total of 4 + 12= 16 electrons).

2) The number of octet electrons is equal to 24. (Carbon wantseight electrons, and each of the oxygens want eight electrons,for a total of 8+16 = 24 electrons).

3) The number of bonding electrons is equal to the octetelectrons minus the valence electrons, or8.

4) The number of bonds is equal to the number of bondingelectrons divided by two, because there are two electrons per

bond. As a result, in CO2, the number of bonds is equal to 4.(Because 8/2 is 4).

5) If we arrange the molecule so that the atoms are held together by four bonds, we find that the only way to do it so that the following pattern: O=C=O, where carbon is double-bonded to both oxygen atoms.

6) The number of nonbonding electrons is equal to the number of valence electrons (from #1) minus the number of bondielectrons (from #3), which in our case equals 16 - 8, or8. Looking at our structure, we see that carbon already has eightelectrons around it. Each oxygen, though, only has four electrons around it. To complete the picture, each oxygen needs totwo sets of nonbonding electrons:

Example:CO2

Video

atheorythatpredictssomemolecular shapes based on the idea that pairs of valenceelectrons surrounding an atom repel each other

There are a whole bunch of common shapes you need to know to accurately think of covalentmolecules. Here they are:

Tetrahedral: Tetrahedral molecules look like pyramids with four faces. Each point on thepyramid corresponds to an atom that's attached to the central atom. Bond angles are 109.5degrees. (NO LONE PAIR)

Trigonal pyramidal: It's like a tetrahedral molecule, except flatter. It looks kind of like asquished pyramid because one of the atoms in the pyramid is replaced with a lone pair.Bond angles are 107.5 degrees (it's less than tetrahedral molecules because the lone pairshoves the other atoms closer to each other). (LONE PAIR)

Trigonal planar: It looks like the hood ornament of a Mercedes automobile, or like a peacesign with that bottom-most line gone. The bond angles are 120 degrees. (NO LONE PAIR)

Bent: They look, well, bent. Bond angles can be either 118 degrees for molecules with onelone pair or 104.5 degrees for molecules with two lone pairs. (LONE PAIR)

Linear: The atoms in the molecule are in a straight line. This can be either because thereare only two atoms in the molecule (in which case there is no bond angle, as there need tobe three atoms to get a bond angle) or because the three atoms are lined up in a straight line(corresponding to a 180 degree bond angle). (NO LONE PAIR)
http://www.youtube.com/watch?v=KJjNfsRfFXUhttp://www.youtube.com/watch?v=KJjNfsRfFXUhttp://www.youtube.com/watch?v=QKoA3fZ29B0&feature=relatedhttp://www.youtube.com/watch?v=QKoA3fZ29B0&feature=related


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Moles, Grams, Avogadros Number

Electron Shielding

Lattice Energy

Mole is the SI base unit used to measure the amount of asubstance whose number of particles is the same as thenumber of atoms in 12 g of carbon-12

Avogadros Number : 6.022 1023, the number of atoms or

molecules in 1 mol

Mole :

N= G/M

N = Number of Mole

G = Grams

M = Molar Mass

the reduction of the attractive force between a positively chargednucleus and its outermost electrons due to the cancellation of someof the positive charge by the negative charges of the inner electrons

The shielding effect describes the decrease in attraction between an electron and the nucleus in any atom with morthan one electron shell.

It is also referred to as the screening effect or atomic shielding.

Shielding electrons are the electrons in the energy levels between the nucleus and the valence electrons. They are c"shielding" electrons because they "shield" the valence electrons from the force of attraction exerted by the positivecharge in the nucleus.

the energy associated with constructing a crystal lattice relative to the energy of allconstituent atoms separated by infinite distances

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