In a chemical reaction, the mass of the reactants will equal the mass of the products.

EXAMPLE
In an experiment, 2.73 g of an oxide of mercury was decomposed to yield 2.53 grams of mercury.
What mass of oxygen was released?

2.73 g – 2.53 g = 0.20 g oxygen

Law of Definite Proportions
A pure compound, whatever its source, always contains definite or constant proportions of the elements by mass.
In a given chemical compound, the elements are always combined in the same proportions by mass.

EXAMPLE
In 1.00 g of NaCl there are 0.3934 g Na and 0.6066 g of chlorine.  What is the ratio of Na to Cl or Cl to Na?

This means that a ratio of 0.3934 g Na/0.6066 g Cl or 0.6485 g Na/g Cl is established.
The law of constant composition means that for any sample of NaCl that's decomposed, we obtain 0.6485 g of Na for every
1.000 g of Cl or 1.542 g of Cl for every 1.000 g of Na.

Law of Multiple proportions:
When two elements form more than one compound, the masses of one element in these compounds for a fixed mass
of the other element are in ratios of small whole numbers.

In carbon monoxide, CO, there are 1.3321 g of O for each 1.0000 g of C.

In carbon dioxide, CO₂, there are 2.6642 g of O for each 1.0000 g of C.
CO₂ contains 2 times the mass of O as is contained in CO for a given mass of C.

Dalton’s Atomic Theory
1. All matter is composed of indivisible atoms. An atom is an extremely small (submicroscopic) particle of matter that takes
part in chemical reactions.

2. An element is a type of matter composed of only one kind of atom, each atom of a given kind has the same properties.

3. A compound is a type of matter composed of atoms of two or more elements which have been chemically combined.

4. A chemical reaction consists of rearrangement of the atoms present in the reacting substances to give a new substance.
The atoms cannot be destroyed or created in this process.

Proton: positively charged particle located inside the nucleus. It has a relative mass of 1.  The proton also carries
one fundamental unit of positive electric charge, +1.

Neutron: particle with no charge located inside the nucleus.  It has a mass slightly larger than the proton but shall
be considered to have a relative mass of 1.

Electron: a very light, negatively charged particle that exists in the region around the atom's positively charged
nucleus.  It has a mass that is 1/1836 or (0.0005447) of the mass of the proton.  An electron has the same amount of
charge as a proton, but it is negative charge, that is, 1-.

Protons, neutron, and electrons are fundamental particles. This means that all protons are alike, all neutrons are alike,
and all electrons are alike in whatever element they are found.

Nucleus: positively charged dense area at the center of the atom.

Element: a substance whose atoms all have the same atomic number.

Sub-atomic particles

Particle	Symbol	Relative Mass	Relative Charge	Location in Atom	Absolute Charge	Mass	Mass in amu
Proton	p+	1	+1	Inside nucleus	+1.60 x 10-19 C	1.67 x 10-27 kg	1.007276
Neutron	n	1	0	Inside nucleus	---	1.67 x 10-27 kg	1.00866490
Electron	e-	0.000545	-1	Outside nucleus	-1.60 x 10-19 C	9.11 x 10-31 kg	0.0005485799

Atomic number (Z): the number of protons in the nucleus.
The atomic number is shown above the elemenal symbol on the periodic table.

For H, Z =1, that is an atom of hydrogen contains 1 proton.

For Na, Z = 11, that is an atom of sodium contains 11 protons.

For Fe, Z = 26, that is an atom of iron contains 26 protons.

Mass Number (A): Number of protons and neutrons in the nucleus.
Isotopes: atoms whose nuclei have the same atomic number but different mass numbers; that is the same number of protons
but different number of neutrons.

Mass number is symbollicaly represented as either a subscript before the symbol, ²²Na, or as a hyphen and number following
the symbol, Na-23.

Mass number - atomic number = numbe of neutrons in the neuleus.

A - Z = number of neutrons

EXAMPLE
How many neutrons are in ²²Na, ²³Na, ³⁵Cl, and ³⁷Cl?

²²Na:     22 – 11 = 12 neutrons

²³Na:     23 – 11 = 12 neutrons

³⁵Cl:     35 - 17 = 18 neutrons

³⁷Cl:     35 - 17 = 20 neutrons
 

The number of electrons in a species can be calculated by subtracting the charge on the species from the atomic number.

Z - Charge = # of electrons

EXAMPLE
How many electrtons are in the sodium cation, Na¹⁺ , and the chloride anion, Cl^1- ?

Na¹⁺:        11 - (+1) = 10 electrons

Cl^1-:        17 - (-1) = 18 electrons

ATOMIC MASSES
What gives mass to the atom?     (PROTON, NEUTRON, & ELECTRON)

Carbon on earth is 98.892% ¹²C, 1.108% ¹³C.

¹²C = 6 protons; 6 neutrons; 6 electrons

¹³C = 6 protons; 7 neutrons; 6 electrons

By international agreement, the current atomic mass standard is the pure isotope of carbon-12 (C-12) which is
assigned a mass of exactly 12 atomic mass units (12 u).

All weights on the periodic table are relative to this value.
Atomic mass unit (amu): one twelfth the mass of a carbon-12 atom. 1 amu = 1.66054 x 10^-24 g. The unit is often
abbreviated as, u.
If 1 atom of ¹²C has a mass of exactly 12 amu then the relative mass of 1 atom of ¹³C is 13.0035 amu.

Atomic mass: the weighted average of the masses of the naturally occurring isotopes of that element.  The atomic mass
is shown below the elemenal symbol on the periodic table.

The atomic mass of hydrogen is 1.0079 u.

The atomic mass of sodium is 22.9898 u.

The atomic mass of iron is 55.847 u.

The atomic masses given for an element on the periodic table are weighted averages of all the stable isopopes of that element.
All atomic masses are averaged because of isotopes.
This value is calcuated by adding the contribution of each iosotpe.

Contribution of isotope = fractional abundance  x  mass of isotope
 

Isotope	Percent  Abundance	Fractional Abundance
Carbon-12	98.892%	0.9882
Carbon-13	1.108%	0.01108

The atomic mass of carbon is:

(0.98892)(12 u) + (0.01108)(13.00335 u) =  11.867 u + 0.1441 u = 12.011 u

EXAMPLE
Naturally occurring chromium is a mixture of: 4.35% ⁵⁰Cr (49.9461 amu), 83.79% ⁵²Cr (51.9405 amu), 9.50% ⁵³Cr (52.9407 amu),
and 2.36 % ⁵⁴Cr (53.9389 amu). What is the atomic mass of chromium?

    Contribution of Cr-50 = (0.0435)(49.9461) = 2.1726 u

   Contribution of Cr-52 = (0.8379)(51.9405) = 43.5209 u

    Contribution of Cr-53 = (0.0950)(52.9407) = 5.0295 u

    Contribution of Cr-54 = (0.0236)(53.9389) = 1.2730 u

    = 2.1726 u + 43.5209 u + 5.0294 u + 1.2730 u = 51.99 u
 

EXAMPLE
Boron has two naturally occurring isotopes ¹⁰B and ¹¹B.  Their masses are 10.01294 u and 11.00931 u respectively.
What is their fractional abundance?

Let X = fractional abundance ¹⁰B ; then 1 - X = fractional abundance ¹¹B.

10.81u = (X)(10.01294 u) + (1 - X)(11.00931 u)

10.81u = 10.01294X + 11.00931 - 11.00931X

11.00931X - 10.01294X = 11.00931- 10.81

0.99637X = 0.19931

X = 0.200

The fractional abundance is:  0.200 ¹⁰B and 0.800 ¹¹B or percent abundance 20.00% B-10 & 80.00% B-11

Elements are placed in the periodic table in order of increasing atomic number (Z).

The periodic table is divided into groups (vertical columns) and periods (horizontal rows).

GROUPS (or families) are vertical columns.

    Group 1 Alkali metals

    Group 2 Alkaline Earth Metals

    Group 17 Halogens

    Group 18 Noble Gases (Inert Gases)

    Groups 3-10 Transition metals

The transition metals take their collective name from their role as a bridge between the chemically active metals of
Groups 1 and 2 and the much less active metals of groups 12, 13, and 14.

    Groups 1, 2, 12 - 18 are referred to a main group elements.

PERIODS are horizontal rows.

There are 7 periods in the present day periodic table.

The long block below the main table consists of the inner transition metals.
    La - Yb Lanthanides
    Ac - No Actinides

Each element in the periodic table is represented by a SYMBOL which most often is based on English or Latin names.
    Hydrogen (Greek hydros genes = "water forming")
    Helium (Greek  helios = "sun")
    Neon (Greek neos = "new")
    Oxygen (Greek oxys - sharp = "acid & genes - forming")
    Gold  (Latin aurum = "shining dawn")
    Chlorine (Greek chloros = "greenish, yellow")
    Carbon  (Latin carbo = "charcoal")
    Mercury (Latin  hydraargyrum = "liquid silver")
    Lead (Latin  plumbum)

Each element is represented by a "box" in the periodic table, and the data shown in the box.

The elements can be identified in three main classes:
    1. Metals: luster, conductor of heat and electricity, malleable (hammered), ductile (drawn into wire)

    2. Nonmetals: non of the above

    3. Metalloid or semimetals: both metallic and nonmetallic properties B, Si, Ge, As, Sb, Te, At

Two (2) elements are liquids at room temperature: Br & Hg

Eleven (11) elements are gases: H₂, He, N₂, O₂, F₂, Ne, Cl₂, Ar, Kr, Xe, Rn

Seven (7) elements exist as diatomic molecules:  Br₂, I₂, N₂, Cl₂, H₂, O₂, F₂ (Memory of the seven diatomic elements can be
aided by the term "Brinclhof")

B₂O₃ ,NH₃, H₂O

Molecules and Molecular Compounds

Molecule is a group of two or more atoms held together in a definite spatial arrangement by forces called covalent bonds.

Molecular compound a compound that has molecules as its smallest characteristic entities.

Empirical formula the simplest formula which can be written for a compound.

Molecular formula the actual number of atoms in a molecule represented by whole number ratio.
 

The molecular formula for glucose is:  C₆H₁₂O₆
The emperical formula for glucose is:   CH₂O

Writing Formulas and Names of Binary Molecular Compounds

BINARY molecules = Compounds of Two Nonmetals
    1. Element to the left in the period named first. HCl: hydrogen named first.

    2. The element in the period below named first. BrCl: bromine is named first.

    3. The other element is named with -ide ending.
        HCl hydrogen chloride
        BrCl bromine chloride

4. When two nonmetals form more than one compound from each other, numerical prefixes are used.
       Number   Prefix
        one           mono-
        two           di-
        three       tri-
        four         tetra-
        five          penta-
        six           hexa-
        seven      hepta-
        eight       octa-
        nine        nona-
        ten          deca-

        NO nitrogen monoxide                  N₂O₅ dinitrogen pentoxide
        N₂O dinitrogen monoxide             PCl₅ phosphorus pentachloride
        NO₂ nitrogen dioxide                     P₂O₅ diphosphorus pentoxide
        N₂O₃ dinitrogen trioxide               SF₆ sulfur hexafluoride
        N₂O₄ dinitrogen tetroxide            Cl₂O₇ dichlorine heptoxide

BINARY MOLECULAR COMMON NAMES
    B₂H₆ Diborane
    CH₄ Methane
    SiH₄ Silane
    NH₃ Ammonia
    PH₃ Phosphine
    H₂O Water
    H₂S Hydrogen sulfide
    HF Hydrogen fluoride
    HCl Hydrogen chloride
    HBr Hydrogen bromide
    HI Hydrogen iodide

Ions and Ionic Compounds
Ion: an electrically charged particle obtained from an atom or chemically bonded group of atoms by adding or
removing electrons.

Anion: negatively charged ions

Cation: positively charged ions

Ionic compound: a compound composed of cations and anions; also called salts.

Formula unit: the group of atoms or ions explicitly symbolized in the formula. The formula unit is "hypothetical,"
because it does not exist as a separate entity.

Nomenclature of Simple  IONIC COMPOUNDS:
Ionic compound composed of a metal cation and a nonmetal anion other than hydroxide (OH^1-) are referred to as salts.
NaCl, CaS, Al(NO₃)₃, NaHCO₃, Fe₃PO₄, FePO₄
Ionic solids with hydroxide as the anion are called bases.
NaOH, Ca(OH)₂, Al(OH)₃, Fe(OH)₂

BINARY Type I Salts
An ionic solid which is composed of only 2 elements with the cation having only one type of charge.
    1. Cation named first and anion named last.
    2. Metal takes its name from the element.
    3. Anion is named by taking the first part of the elements name and adding "ide".

        Group IA metals (Alkali metals) all form cations with a 1+ charge.
                Li¹⁺, Na¹⁺, K¹⁺
        Group IIA (alkline earth metals) all form cations with a 2+ charge.
                Mg²⁺, Ca²⁺, Ba²⁺
        Aluminum forms only the 3+ cation. Al³⁺

    KF potassium fluoride        MgS magnesium sulfide
    LiH lithium hydride             NaH sodium hydride
    Al₂O₃ aluminum oxide       CaO calcium oxide

BINARY Type II Salts
An ionic solid composed of only 2 elements but the cation can have more than one type of charge.
    1. Metal takes its name from the element.
    2. Immediately following the metal a Roman numeral is used to indicate the charge. Parentheses are used to enclose the
        Roman numeral.   There is no space between the metal and the opening parenthesis. There is a space between the
        closing parenthesis and the anion name.
    3. Anion is named by taking the first part of the elements name and adding "ide".

    FeCl₂ iron(II) chloride            FeCl₃ iron(III) chloride
    CrO chromium(II) oxide         Cr₂O₃ chromium(III) oxide        CrO₃ chromium(VI) oxide
    Cu₂S copper(I) sulfide           CuS copper(II) sulfide
    VF₅ vanadium(V) fluoride
    Nb₂O₅ niobium(V) oxide

POLYATOMIC IONS
Cations
Ammonium NH₄¹⁺
Anions
Acetate C₂H₃O₂^1-
Carbonate CO₃^2-
Hydrogen carbonate  (or bicarbonate) HCO₃^1-
Hypochlorite ClO^1-
Chlorite ClO₂^1-
Chlorate ClO₃^1-
Perchlorate ClO₄^1-
Chromate CrO₄^2-
Dichromate Cr₂O₇^2-
Cyanate OCN^1-
Thiocyanate SCN^1-
Cyanide CN^1-
Hydroxide OH^1-
Nitrite NO₂^1-
Nitrate NO₃^1-
Oxalate C₂O₄^2-
Permanganate MnO₄^1-
Phosphate PO₄^3-
Hydrogen phosphate HPO₄^2-
Dihydrogen phosphate H₂PO₄^1-
Sulfite SO₃^2-
Hydrogen sulfite  (or bisulfite) HSO₃^-1
Sulfate SO₄^2-
Hydrogen sulfate (or bisulfate) HSO₄^-1
Thiosulfate S₂O₃^2-

Hydrates
Hydrate A hydrate is a crystalline compound with a fixed number of water molecules weakly bound within the crystal.
The water in the compound is referred to as waters of hydration.
Some examples of hydrates are:
CuSO₄• 5 H₂O    Copper(II) sulfate pentahydrate
NiSO₄• 6 H₂O    Nickel(II) sulfate hexahydrate
AlK(SO₄)₂• 12 H₂O    Aluminum potassium sulfate dodecahydrate

Acids, Bases, and Salts
ACID: a molecular compound which ionizes, or breaks up, in water to form a solution containing H⁺ ions (protons) and anions.

TERNARY ACID: An acid composed of three elements: hydrogen and two other nonmetals.  Most are oxoacids.

OXOACID: a ternary acid containing hydrogen, oxygen, and another element (often called the central atom).

BASE: a compound which ionizes in water to form a solution containing OH^1- anions and cations.

SALT: the ionic compound formed from the reaction of an acid and a base.

The salt is composed of the cation of the base and the anion of the acid.

Formulas and Names of Acids, Bases, and Salts
The rules for naming acids depends on whether or not the anion contains oxygen.
    1. If the anion does not contain oxygen, the acid is named with the prefix hydro- and the suffix -ic.
        (Also called binary acids.)
        HCl is a gas, but when dissolved in water is hydrochloric acid.
        HCN hydrocyanic acid
        H₂S hydrosulfuric acid
    2. If the anion contains oxygen the acid name is formed from the root name for the anion with the suffix
        -ic for -ate anions and the suffix -ous for -ite anions. Also called OXOACIDS
                "-ic" acids are related to the "-ate" anions
                "-ous" acids are related to the "ite" anions
 

ACID FORMULA	ACID NAME	ANION NAME	ANION FORMULA
H2SO4	sulfuric acid	sulfate	SO42-
H2SO3	sulfurous acid	sulfite	SO32-
H2CO3	carbonic acid	carbonate	CO32-
HNO3	nitric acid	nitrate	NO31-
HNO2	nitrous acid	nitrite	NO21-
HClO4	perchloric acid	perchlorate	ClO41-
HClO3	chloric acid	chlorate	ClO31-
HClO2	chlorous acid	chlorite	ClO21-
HClO	hypochlorous acid	hypochlorite	ClO1-
HC2H3O2	acetic acid	acetate	C2H3O21-
H3PO4	phosphoric acid	phosphate	PO43-

There are 6 Strong acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄

There are 9 Strong bases: LiOH, NaOH, KOH, RbOH, CsOH, Mg(OH)₂, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂