Unit 6: Chemical formula and Chemical Compounds

Chapter 7

Chemical formula

The formula of a covalent compound (molecule) indicates the number of atoms of each element contained in a single molecule of the compound

Monatomic Ions

Ions formed a single atom

Cation

A positive ion, metals tend to lose one or more electrons.

Anion

A negative ion, Nonmetals tend to gain one or more electrons.

Naming Monatomic Ions: Cation

By the elements name. (Na⁺ sodium ion)

Naming Monatomic Ions: Anion

By deleting the ending of the elements name, and then add ending -ide to the root name. (Cl^- , chloride)

Binary compounds

Compounds composed of two different elements

Binary covalent compounds

H₂O, BF₃

Binary ionic compounds

KI, CaCl₂

Naming Binary Ionic compounds

name of metal + (root name of nonmetal + ide). Ex: Al₂O₃ aluminum oxide, CaS calcium sulfide, KBr potassium bromide

The Stock System Of Nomenclature

Used for metals that have different charges (most transition metals, Pb and Sn).

Roman numeral

Used to indicate a cations charge. it is inclosed in parentheses and placed immediately after the metals name. Ex: Fe₂⁺+O- Iron (II) Oxide

Naming compounds containing polyatomic ions

Name of the cation + name of the anion. Ex: MgSO₄ Magnesium sulfate

Predict the formula of ionic compounds

the total number of positive charges and negative charges must be equal

Cross over method

Used to determine the ratio of cations to anions when the number of charges is different. Example: Mg₂+ SO₂ —> MgSO₄; Al₃+ N₃^- —> AlN

Ba(OH)2

Barium Hydroxide

Cr2O3

Chromium(III) oxide

(NH4)3PO4

Ammonium Phosphate

Naming Binary Covalent Compounds

(prefix if more than one + name of the less electronegative elements)+(prefix + root name of the more electronegative element + ide)

Binary Acids

Containing two elements, usually hydrogen and one of the halogens. (hydrogen + root name of the halogens + ic) + acid). Example: HF; hydrofluoric acid

Naming oxyacids

Contain hydrogen, oxygen, [Root name of the third element + ic (ous)] + acid. Example: H₂SO₄; sulfuric acid (containing sulfate). H₂SO₃, sulfurous acid (contain sulfite)

Using Chemical Formula

The following values for a given compound can be calculated. Formula mass, molar mass, and percentage composition

Formula mass

the sum of the average atomic masses of all the atoms in the formula. Unit: amu

Molar mass

The sum of the masses of the elements in one mole of the given compound. It is numerically equal to its formula mass. Unit: g/mol

Percentage composition

The % by mass of each element in a compound. Element% = total mass of the element / total mass of the compound x 100%

Empirical formula

Indicates the simplest whole-number ratio of atoms in a given compound, it’s the formula of ionic compounds

Molecular formulas

Indicates the types of numbers of atoms in a single molecule of a covalent bond. X= formula mass/ empirical formula mass

Nitrite

NO2-

Numerical prefixes

Mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca