LECTURE 1

Contents:• Types of Matter• Atoms & Atomic Theory• Atomic Masses• Naming Compounds• Mole Concept

• MatterMatter is anything that has mass and occupies space. • It exist in 3 phases:

Solid – fixed shape and volume. Liquid – fixed volume & not rigid in shape (shape of the

container). Gas – neither fixed volume nor a rigid shape (depend on

the volume and shape of the container)

• Matter can be classified into two categories: Pure substance – fixed composition and unique set of

properties. Mixtures – composed two or more substances.

Elements • A type of matter that cannot be broken down into 2 or

more pure substance. • consists of only one kind of atoms. All atoms of a given

element are identical, having the same size, mass and chemical properties.

• The atoms of one element are different from the atoms of all other elements – each elements is unique.

• Example: Copper (Cu) – use in electrical wiring, jewelry, water

pipe. Aluminium (Al) – household utensils

Compound • Pure substance that composed of two or more

different elements that are chemically bound together. Example: Water contain oxygen (O) and hydrogen (H).

• Compounds have fixed compositions – always contain the same elements in the same percentages by mass.

Water contain precisely 11.19% hydrogen and 88.81% oxygen.

• The properties of compounds are different from those the elements they contain. Example: salt (sodium chloride).

Mixtures • Contain two or more substances combined in such a

way that each substance retains its chemical identity. Copper sulfate do not react with sand when it

combine/shake together.

• There are two types of mixtures:

a.a. HomogeneousHomogeneous – or uniform mixtures which the composition is the same throughout. Also called as solution (contain solvent and solute).

b.b. HeterogeneousHeterogeneous – or nonuniform mixtures which the composition varies throughout. Most rocks fall into this categories.

To learn about matter, you must also familiar with:• AtomsAtoms - which are composed of electrons, protons

and neutrons.• MoleculesMolecules - the building blocks of several element and

many compounds. Molecular substances can be identified by their formulae or their names.

• IonsIons - species of opposite charge found in all ionic compounds. Using relatively simple principles, it is possible to derive the formulae and names of ionic compounds.

Postulates of the Dalton’s Atomic TheoryPostulates of the Dalton’s Atomic Theory

1. All matter consists of atomsatoms.

2. Atoms of one element cannotcannot be converted into atoms of another element.

3. Atoms of an element are identicalidentical in mass and other properties and are different from atoms of any other element.

4.4. CompoundsCompounds result from the chemical combination of a specific ratio of atoms of different elements.

Some features of Dalton’s

atomic theory

Some features of Dalton’s

atomic theory

8 X2Y16 X 8 Y+

Structure of the AtomStructure of the Atom• An atomatom is an electrically neutral, spherical entity

composed of a positively charged central nucleus surrounded by one or more negatively charged electrons.

• An atomic nucleus consists of protons and neutrons (except H).

Proton (p+) has a positive charge Neutron (n0) has no charge Electron (e-) has a negative charge

• An atom is neutralneutral because the number of protons in nucleus is equals the number of electrons surrounding the nucleus.

Electrons Electrons • Are common to all atoms, carry a unit negative charge (-

1) and have a very small mass, roughly 1/2000 that of the lightest atom.

• Every atom contains a definite number of electrons. Hydrogen contain 1 electron Uranium contain 92 electrons

• Electrons are found in the outer regions of the atom, where they form what amounts to a cloud of negative charge.

Protons and Neutrons; the atomic nucleusProtons and Neutrons; the atomic nucleus• Proton, which has a mass nearly equal to that of an

ordinary hydrogen atom.• The proton carries a unit positive charge (+1), equal in

magnitude to that of the electron (-1).• The neutron is an uncharges particle with a mass slightly

greater than that of a proton.• Because proton and neutrons are much heavier than

electrons, most of the mass of an atom (>99.9%) is concentrated in the nucleus, even though the volume of the nucleus is much smaller than that of the atom.

Atomic Number, Mass Number and Atomic SymbolAtomic Number, Mass Number and Atomic Symbol• Atomic number (Z)- Atomic number (Z)- number of protons in nucleus of

each of its atoms.• Example: C atoms (Z=6) have 6 protons• Mass number (A) Mass number (A) – the total number of proton and

neutrons in the nucleus of an atom.• The nuclear mass number and charge are often written

with the atomic symbolatomic symbol. Atomic symbol – element symbol based on its English, Latin

or Greek name. Atomic number (Z) is written as a left subscript Mass number (A) – is written as left superscript

H11 Cl35

17 C126

U23592 Sr90

38

XAZ

Mass Number

Atomic NumberElement Symbol

or

Isotopes and Atomic Masses of the ElementsIsotopes and Atomic Masses of the Elements• IsotopesIsotopes – all atoms of an element are identical in atomic

number but not in mass number (different numbers of neutrons).

• Example: Carbon (Z=6)Carbon (Z=6) – have 6 protons and 6 neutrons. A small % have 7 neutron (A=13) and 8 neutron (A=14). Carbon have three isotopes – 1212C, C, 1313C and C and 1414CC

• The chemical properties of an element are primarily determine by the no of electron.

• So, all isotopes of an element have nearly identical chemical behavior (even though have different masses).

H11 H21 H

31 Cl35

17 Cl3717

6 protons, 8 (14 - 6) neutrons, 6 electrons

6 protons, 5 (11 - 6) neutrons, 6 electrons

How many protons, neutrons, and electrons are in C14

6 ?

How many protons, neutrons, and electrons are in C11

6 ?

13 protons, 14 (27 - 13) neutrons, 10 (13 – 3) electrons

16 protons, 16 (32 - 16) neutrons, 18 (16-2) electrons

How many protons, neutrons, and electrons are in Al27

13?

3+

How many protons, neutrons, and electrons are in S32

16?

2-

Atomic Masses; the Carbon-12 ScaleAtomic Masses; the Carbon-12 Scale

• Individual atoms are far too small to be weighed on a balance.Individual atoms are far too small to be weighed on a balance.

• Atomic massAtomic mass is the mass of an atom in atomic mass units (amu).

• The atomic mass of an element indicates how heavy, on the average, one atom of that element is compared with an atom of another element.

• To set up a scale of atomic mass, it is needed a standard value for one particular species.

• One atomic mass unit atomic mass unit is defined as a mass exactly equal to one-twelfth the mass of one carbon-12 atom.

On this scale1H = 1.008 amu

16O = 16.00 amu

1 amu = 1/12 x mass of one C-12 atom

In the periodic table, atomic masses are listed directly below the symbol of the

element

In the periodic table, atomic masses are listed directly below the symbol of the

element

Relative Atomic Mass, Relative Atomic Mass, AArr ; Relative Molecule Mass, ; Relative Molecule Mass, MMrr

• Some definitions of atomic and molecular masses:Some definitions of atomic and molecular masses:

• If the mass ratio of one atom of an element to one atom of If the mass ratio of one atom of an element to one atom of carbon-12 is known, the relative atomic mass of the element can carbon-12 is known, the relative atomic mass of the element can be calculated.be calculated.

Relative atomic mass, Relative atomic mass, AArr of an = of an = element Xelement X

Mass of one atom of XMass of one atom of X 1/12 x mass of one 1/12 x mass of one 1212C atomC atom

Relative molecular mass, Relative molecular mass, MMrr of a = of a = compound W compound W

Mass of one molecule of WMass of one molecule of W 1/12 x mass of one 1/12 x mass of one 1212C atomC atom

The mass ratio of one atom of nitrogen to one atom of carbon-12 is 1.24899. What is the relative mass of nitrogen?

Start from the definition of relative atomic mass of an element

= 12 x 1.24899

= 1.24899Mass of one atom of Nmass of one atom of carbon-12

Relative atomic mass of N = Mass of one atom of N 1/12 x mass of one 12C atom

= 14.98788

• The amount of each isotope of an element expressed in percentage is called the relative abundance the relative abundance or isotopic abundance of that element.

• The total relative abundance is 100%.

• Element that have more than one isotope – measure the average mass for all occurring mixture of isotopes.

• If an element has n isotopes, the average atomic mass of the elements is:

Fraction abundance, f = Percentage of isotope 100

• Example: Lithium

(7.42 x 6.015) + (92.58 x 7.016)100 = 6.941 amu

Tentukan jisim atom relatif, Ar bagi unsur Neon yang diketahui mempunyai tiga isotop iaitu 20Ne, 21Ne dan 22Ne dengan peratus kelimpahan masing-masing 90. 92%, 0.26% dan 8.82%.

= 20.18

90.92100

+Ar Ne = ( )x 20 ( )x 210.26100

( )x 228.82100

+

• Relative masses of individual atoms can be determined using a mass spectrometer.

• The substance to be analysed must first be vapourised to gaseous atoms or molecules in the vapourisation chambervapourisation chamber.

• The spectrometer is connected to a vacuum pump vacuum pump so that the air molecules will not interfere with incoming particles.

• Gaseous atoms or molecules are ionised in the ionisation ionisation chamberchamber as a result of bombardment by the beam of high energy electrons emitted by an electron gunelectron gun. When atom loses electron, positive ion are produced. Example: C+ ion is formed when an electron is removed from a

carbon atom.

• In the acceleration chamberacceleration chamber, the cation formed are accelerated by a potential difference of 500 to 2000V toward a magnetic magnetic field.field.

• The magnetic field deflects the ions from their straight-line path (depends on the mass to charge ratio of the ions). The path of more massive ions curve less than the less massive ions (species can be separate).

• All ions will be directed to the detectordetector plate where they produce a weak signal or current.

• Mass spectrum Mass spectrum showing peaks of various heights at certain mass/charge (m/e) values.

The mass spectrometerThe mass spectrometer

Mass spectrum of chlorine

Chlorine contains only two isotopes: 34.97 amu (75.53%) and 36.97 amu (24.47%)

Average atomic mass Cl Average atomic mass Cl

= (34.97 x 75.53) + (36.97 x 24.47) 100 100

= 35.46 amu

Names and Formulas of Names and Formulas of Ionic CompoundsIonic Compounds

• Many ionic compound are binary compound binary compound or compound formed from just two element

Metal (cation)– many metal names end in –ium–ium Nonmetal (anion) – adds the suffix –ide –ide in the end of

nonmetal name

• Ternary compound Ternary compound – compounds consisting of three elements Anion groups containing different elements also used ––

ideide Example: Lithium hydroxide (LiOH) Potassium cyanide (KCN)

Names and Formulas of Names and Formulas of Ionic CompoundsIonic Compounds

Names and Formulas of Names and Formulas of Ionic CompoundsIonic Compounds

• Compound with metal that can form more than one Compound with metal that can form more than one ionion Metal in transition element (B groups) Example: Iron can form FeFe2+2+ and FeFe3+3+ ion. When iron react with chlorine, FeClFeCl22 (iron(II)chloride)

and FeClFeCl33 (iron (III)chloride).

Common names for the ion with the lower charge – ous– ous for the ion with the higher charge – ic– ic

• Families of Oxoanions - Families of Oxoanions - Usually nonmetal, is bonded to one or more oxygen atoms. The ion more O atoms takes the nonmetal root, -ate-ate The ion fewer O atoms takes the nonmetal root, -ite-ite

Names and Formulas of Names and Formulas of Ionic CompoundsIonic Compounds

ClO4- is perchlorate ion

ClO3- is chlorate

ClO2- is chlorite

ClO- is hypochlorite

ClO4- is perchlorate ion

ClO3- is chlorate

ClO2- is chlorite

ClO- is hypochlorite

• If have four oxoanions in the family:

Ammonium NH4+ Chlorate ClO3

- Peroxide O2-2

Acetate CH3COO- Perchlorate ClO4- Chromate CrO4

-2

Nitrate NO3- Permanganate MnO4

- Dichromate Cr2O7-2

Nitrite NO2- Carbonate CO3

-2 Silicate SiO3-2

Hydroxide OH- Sulfate SO4-2 Phosphate PO4

-3

Hypochlorite ClO- Sulfite SO3-2 Arsenate AsO4

-3

Chlorite ClO2- Thiosulfate S2O3

-2 Arsenite AsO3-3

Cyanate CN- Thiocyanate SCN- Borate BO3-3

Bicarbonate HCO3- Bisulfate HSO4

- Bisulfite HSO3

• Compound composed of nonmetallic elements. • Many molecular compound are binary compound.• Similar to naming binary ionic compounds. • Adds the suffix –ide –ide in the end of second element.• Example:

Names and Formulas of Names and Formulas of Molecular CompoundsMolecular Compounds

HI hydrogen iodide

NF3 nitrogen trifluoride

SO2 sulfur dioxide

N2Cl4 dinitrogen tetrachloride

NO2 nitrogen dioxide

N2O dinitrogen monoxide

TOXIC!

Laughing Gas

• To avoid confusing in naming the compound, Greek prefixes has been used to denote the number of atoms of each element present.

Names and Formulas of Names and Formulas of Molecular CompoundsMolecular Compounds

• AcidAcid – a substance that yields hydrogen ion (H+) when dissolved in water.

• Two common types of acid: Binary acid Binary acid solution form when certain gaseous compounds

dissolved in water.

OxoacidOxoacid – similar to oxoanions except Suffix – ate – ate becomes – ic– ic in the acid Suffix – ite– ite becomes – ous– ous in the acid

Names and Formulas of Names and Formulas of Acids and Bases Acids and Bases

Name of Anion

Name of Acid Examples

.....-ide Hydro.....-ic acidHCN(aq) cyanide → hydrocyanic acid HBr(aq) bromide → hydrobromic acid

Per .....-ate Per .....-ic acid HClO4 perchlorate → perchloric acid

.....-ate .....-ic acidHClO3 chlorate → chloric acidH2SO4 sulfate → sulfuric acid

.....-ite .....-ous acidHClO2 chlorite → chlorous acidH2SO3 sulfite → sulfurous acid

Hypo...-ite Hypo....-ous acidHClO hypochlorite → hypochlorous acid

• BaseBase – a substance that yields hydroxide ion (OH-) when dissolved in water.

Names and Formulas of Names and Formulas of Acids and Bases Acids and Bases

• The molemole (mol) is the amount of a substance that contains the same number of particles (atoms, molecules or ions) that exists in exactly 12.00 grams of 12C.

• The definition specifies the number of objects in a fixed mass of substance.

• A mole represents 6.022 x 1023 particles, whatever they may be. Therefore, 1 mole of substance = fixed number of chemical entities and has a fixed mass.

Molar massMolar mass is the mass of 1 mole of in gramsionsAtomsMolecules

1 mole 12C atoms = 6.022 x 1023 atoms = 12.00 g

1 12C atom = 12.00 amu

1 mole 12C atoms = 12.00 g 12C

1 mole lithium atoms = 6.941 g of Li

Mass (g) Mass (g) = no. of moles x no of grams1 mol

No. of moles No. of moles = mass (g) x 1 mol no. of grams

• Convert between amount (mol) and mass (g), use molar mass ( M in g/mol)

No. of entities No. of entities = no. of moles x 6.022 x 1023 entities no. of grams

No. of moles No. of moles = no. of entities x 1 mol 6.022 x 1023 entities

• Convert between amount (mol) and no. of entities, use Avogadro’s number (6.022 x 1023 entities)

(1)(1)

(2)(2)

(3)(3)

(4)(4)

• Convert between number of entities and mass, first convert to number of moles.

No. of atoms No. of atoms = mass (g) x 1 mol x 6.022 x 1023 entities no. of grams 1 mol

(5)(5)

Berapakah bilangan atom H yang terdapat di dalam 1 mol gas NH3?

1 mol NH3 mengandungi 3 mol atom H

Bilangan atom H dalam 1 mol NH3

= 3 x 6.023 x 1023 = 1.807 x 1024 atom

Hitung bilangan ion Ca2+ dan ion Cl- dalam 1 mol CaCl2

1 mol CaCl2 mengandungi 1 mol ion Ca2+ dan 2 mol ion Cl-

= 2 x 6.023 x 1023 = 1.205 x 1024 atom

Bilangan ion Ca2+ = 6.023 x 1023

Bilangan ion Cl-

Acetylsalicylic acid, C9H8O4, is the active ingredient of aspirin.

a.What is the mass in grams of 0.509 mol of Acetylsalicylic acid?b.How many moles of C9H8O4 are in 1 g sample of aspirin that contains 91.6% by mass of C9H8O4?

= [9(12.01) + 8(1.008) + 4(16.00)] g/mol = 180.15 g/mol

The molar mass of C9H8O4

a. 0.509 mol x 180.15 g = 91.7g 1 mol

b. 1.000 g x 0.916 x 1 mol = 5.08 x 10-3 mol 180.15 g

The relationships between mass (m in grams) of an element and number of moles of an element (n) and between number of

moles of an element and number of atoms (N) of an element.

M= molar mass in g/mol

NA = Avogadro’s number

Do You Understand Molar Mass?

How many atoms are in 0.551 g of potassium (K) ?

1 mol K = 39.10 g K

1 mol K = 6.022 x 1023 atoms K

0.551 g K 1 mol K39.10 g K

x x 6.022 x 1023 atoms K1 mol K

= 8.49 x 1021 atoms K