list the 3 main types of subatomic particles and indicate the ...objective 13b 45 objective 13c...

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Module 1C – Basic Chemistry

Chemistry – the scientific study of the structure and properties of matter

Why do we study chemistry in a biology course?All living organisms are composed of chemicals. To understand life, we must understand the structure, function, and properties of these chemicals.

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Objective # 6

List the 3 main types of subatomic particles and indicate the mass and electrical charge of each.

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Objective 6

00.00055-1eElectron

11.008670nNeutron

11.00728+1pProton

Mass Number

Mass (Daltons)

ChargeSymbolName

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Objective # 7

Describe the basic structure of the atom and be able to define the following terms: nucleus, orbital, energy level, isotope, and ion.

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Objective 7

Each atom is composed of:Protons and neutrons which are densely packed together in the central part of the atom called the nucleus.Electrons which are in constant motion around the nucleus.

[Note: most hydrogen atoms have no neutrons and atoms can lose some or all of their electrons]

6Proton(Positive charge)

Neutron(No charge)

Electron(Negative charge)

Hydrogen1 Proton1 Electron

Oxygen8 Protons8 Neutrons8 Electrons

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Objective 7

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Objective 7

As electrons move around the nucleus, they do not follow a specific path and it is impossible to say exactly where any specific electron is at any given time. However, the volume of space where there is a 90% chance of finding a particular electron is called its orbital.

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Objective 7

Orbitals:hold a maximum of 2 electrons each.come in a variety of shapes, which are represented by probability clouds.several orbitals may be the same average distance from the nucleus and thus contain electrons of the same average energy. Such electrons are said to occupy the same energy level or shell.Energy levels or shells are often represented as concentric circles around the nucleus

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Objective 7

The first energy level has one spherical orbital:

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10

Objective 7The second energy level has 1 spherical orbital (2s) and 3 dumbbell-shaped orbitals (2p):


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Objective 7

Here you can see a composite of all 5 orbitals found in the first 2 energy levels:

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Objective 7

The higher the energy level, the farther from the nucleus the electrons tend to be , and the more energy they have:

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Objective 7

Rules for filling energy levels:The first electrons enter the K shell, up to a maximum of 2.The next electrons enter the L shell, up to a maximum of 8.

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Objective 7

The pattern for filling higher shells becomes more complex and will not concern us. However, what you should remember is that even though any shell beyond L can hold more than 8 electrons, it will not hold more than 8 when it is the outermost shell.

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Objective 7

Atoms that have the same number of protons but different numbers of neutrons are called isotopes:

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Carbon-12 Carbon-13 Carbon-14


Isotopes of Carbon

6 protons 6 protons 6 protons7 neutrons 8 neutrons6 neutrons6 electrons6 electrons 6 electrons

Objective 7

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Objective 7

Normally, the number of electrons in an atom equals the number of protons and the overall charge of the atom is zero.

However, atoms often gain or lose electrons:If an atom gains electrons, it will have an extra negative charge for each electron gained.If an atom loses electrons, it will have an extra positive charge for each electron lost.

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Objective 7

The gain of electron(s) is called reductionand the loss of electrons is called oxidation.Atoms that have gained or lost electrons and are no longer electrically neutral are called ions:

positive ions = cationsnegative ions = anions

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++

–

Oxidized Reduced

Objective 7

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20

Objective # 8

Define the term “element” and know the names and chemical symbols of the principle elements found in living organisms.

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Objective 8

Element:A substance composed of only one type of atom – i.e. all the atoms have the same number of protons. All atoms of a given element have the same number of protons. However, the number of neutrons and electrons can vary.

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Objective 8

A copy of the Periodic Table can be seen on the next slide. Each box in the table represents one element.Elements found in living organisms in more than trace amounts are shaded in green . Of these, 4 elements (carbon, hydrogen, oxygen, and nitrogen) make up about 96% of the mass of living organisms.

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Objective 8

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Objective # 9

Be able to determine the number of protons, neutrons, and electrons in an atom if you know its atomic number, atomic mass, and overall charge. Also be able to determine the number of electrons in each energy level of an atom if you know the total number of electrons present.

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Objective 9

# p = atomic number# n = atomic mass – atomic number# e:If overall charge is 0, #e = #pIf overall charge is +, #e = #p minus one for each overall + chargeIf overall charge is -, #e = #p plus one for each overall - charge

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Objective # 10

Define the term “molecule” and explain how the molecular formula (or chemical formula) and the structural formula are used to provide information about a molecule.

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Objective 10

Molecule: a unit composed of two or more atoms joined together by chemical bonds:Molecular formula or chemical formula:tells us what types of atoms and how many of each are joined together.Structural formula: shows us the actual arrangement of the atoms.

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H2CO3Carbonic acid

O

O

OC

H

H

Objective 10

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Objective # 11

Explain the difference between an element, a compound, and a mixture.

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Objective 11

Element: a substance composed of only one type of atom (all the atoms have the same number of protons). The atoms may occur signally, or they may be joined to form molecules. The smallest unit of an element that retains the properties of the element is an atom. e.g. hydrogen

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Objective 11

Compound: a substance composed of 2 or more elements that have been joined by chemical bonds. The smallest unit of a compound that retains the properties of the compound is a molecule. e.g. waterMixture: a combination of 2 or more substances that do NOT chemically combine and retain their individual properties. e.g. sugar mixed with salt

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Objective # 12

Explain how the number of electrons in the outermost shell of an atom affects the number and type of chemical bonds the atom can form.

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Objective 12

Electrons in the outermost shell are called:valence electrons

Atoms join together in ways that give each atom a stable outer shell of electrons:If the first shell is the outer shell, it is stable with 2 electrons.If any other shell is the outer shell, it is stable with 8 electrons.

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Nonreactive Reactive

Helium Nitrogen

2 protons2 neutrons2 electrons

7 protons7 neutrons7 electrons

KK

L

2+ 7+


Atoms that lack a stable outer shell of electrons are reactive:

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Objective 12

How can an atom obtain a stable outer shell of electrons if it doesn’t already have one?Gain electronsLose electronsShare electrons

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Objective 12

Different atoms attract their outer electrons with different intensity. The electronegativity of an atom is the amount of energy needed to remove electrons. The more strongly an atom attracts electrons, the higher its electronegativity.

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Objective 12

In general:The closer the electrons are to the nucleus, the higher the electronegativity.The more nearly full the shell is, the higher the electronegativity.

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Objective 12

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Objective # 13

Discuss the mechanism involved in forming the following types of chemical bonds, describe their characteristics, and be able to give examples of each:

a) Ionic bondb) Nonpolar covalent bondc) Polar covalent bondd) Hydrogen bond

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Objective 13a

Ionic bond: If an atom with a very high electronegativity comes near an atom with a very low electronegativity, there may be a transfer of electrons from the 2nd atom to the 1st to give both atoms a stable outer shell.The transfer of electrons produces oppositely charged ions that attract each other to form an ionic bond. e.g. Na and Cl

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Objective 13aFormation of Ionic Bonds – NaCl


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Objective 13a

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Objective 13b

Nonpolar covalent bond:If 2 atoms with the same electronegativity come near each other, neither can remove electrons from the other. However, they may share electrons to obtain a stable outer shell.Since the atoms have the same electronegativity the electrons are shared equally. e.g. two H atoms

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H2 (hydrogen gas)

Non-polar Covalent bond

+ +

–

–


Objective 13b

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Objective 13c

Polar covalent bond:If 2 atoms have different electronegativities, but the difference is not large enough to allow one atom to remove electrons from the other, they may share electrons unequally.The electrons tend to stay closer to the atom with the higher electronegativity. e.g. H2O:

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δ–δ+

Oxygen

Hydrogen

HydrogenPolar Covalent Bond

8+8n

+

+

δ–δ+


Objective 13c

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Objective 13b

Atoms that share one pair of electrons are joined by a single covalent bondAtoms that share 2 pairs of electrons are joined by a double covalent bondAtoms that share 3 pairs of electrons are joined by a triple covalent bond

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Objective 13b

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Objective 13d

Hydrogen bond:The weak attraction between a covalently bound H atom with a slight positive charge and another covalently bound atom with a slight negative charge.May occur between different molecules or between different parts of the same molecule:

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Objective 13d

Hydrogen bonds can form between 2 different molecules

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Objective 13d

Hydrogen bonds can also form between different parts of the same molecule

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Objective 13

Electrostatic bonds are formed by an attraction between opposite charges:Hydrogen bondsIonic bondsCovalent bonds are formed by a sharing of electrons:Polar covalent – unequal sharingNonpolar covalent – equal sharing

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Objective # 14

Describe the structure of the water molecule. List and describe the properties of water, and explain why these properties are so important to all living organisms.

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δ–δ+

Oxygen

Hydrogen

HydrogenWater Molecule

8+8n

+

+

δ–δ+


Objective 14

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Objective 14

Water molecules are drawn up a narrow tube

Capillarity

Surface water molecules cling to each other

Surface tension

Water molecules attract other charged substances

Adhesion

Water molecules attract other water molecules

Cohesion

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Objective 14

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Objective 14

A large amount of heat needed to change water from a liquid to a gas

High heat of vaporization

A large amount of heat needed to change water from a solid to a liquid

High heat of fusion

A large amount of heat must be absorbed or lost to change the temperature of water

High specific heat

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Objective 14

Substances repelled by water are called hydrophobic

Repels nonpolar molecules

Substances attracted to water are called hydrophilic

Dissolves ions and polar molecules

Below 0oC a regular crystalline structure forms

Lower density as a solid

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Stablehydrogen

bondsUnstable hydrogen

bonds


Liquid water Ice

Objective 14

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Objective 14


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Objective # 15

Describe the process of dissociation and be able to distinguish between acids, bases, and salts.

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Objective 15

Because of the polar structure of water, many ionic and polar substances are pulled apart into oppositely charged ions when they dissolve in water. This is called ionization or dissociation.

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Objective 15

Substances held together by relatively weak ionic bonds show a large amount of dissociation in water:

NaCl → Na+ + Cl-

These substances are called salts. Because they are good conductors of electricity, they are also called electrolytes.

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Objective 15

Substances held together by stronger covalent bonds may also show some dissociation when dissolved in water:

CH3COOH → CH3COO- + H+

In fact, water itself undergoes a small amount of dissociation:

H2O → H+ + OH-

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Objective 15

In pure water:[H+] = [OH-] = 1 x 10-7 M

In all aqueous solutions:[H+] [OH-] = 1 x 10-14 M2

This means as the [H+] increases, [OH-] decreases, and vice versa.

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Objective 15

Substances that increase the [H+] of a solution are called acids:

HCl → H+ + Cl-

Substances that decrease the [H+] of a solution are called bases:

NaOH → Na+ + OH-

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Objective # 16

Describe the pH scale and know how to use it.

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Objective 16

pH is used to measure how acidic or basic a solution is.pH is defined as the negative log of the [H+] of a solution.If a solution has a [OH-] of 1x10-3 M,What is its [H+]?What is its pH?

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Objective 16

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Objective # 17

Explain the role that buffers play in living organisms.

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Objective 17

A buffer is a substance that helps minimize the change in the pH of a solution when acids or bases are added.Buffers work by releasing H+ when their concentration falls and absorbing H+ when their concentration rises.

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Objective 17

Relationship between pH andamount of base added

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Objective 17

Buffers are important to living organisms because most cells can survive and function normally only within a relatively narrow pH range.

list the 3 main types of subatomic particles and indicate the ...objective 13b 45 objective 13c...

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