chemical substances formulas and names

Chemical formula

a notation that uses atomic symbols with numerical subscripts to convey the relative proportions of atoms of the different elements in the substance

Molecule

A molecule is a definite group of atoms that are chemically bonded together that is tightly connected by attractive forces

Molecular substance

A molecular substance is a substance that is composed of molecules, all of which are alike

Polymers

are very large molecules that are made up of a number of smaller molecules repeatedly linked together

Monomers

are the small molecules that are linked together to form the polymer

Structural formula

A structural formula is a chemical formula that shows how the atoms are bonded to one another in a molecule

Polyatomic ion

A polyatomic ion is an ion consisting of two or more atoms chemically bonded together and carrying a net electric charge

Ion

An ion is an electrically charged particle obtained from an atom or chemically bonded group of atoms by adding or removing electrons .N

Naming of ionic compounds

• name an ionic compound by giving the name of the cation followed by the name of the anion

Rules for naming monatomic ions

1. Monatomi cations are named after the element if there is only one such ion. Example Al3+ is called aluminium ion.

2. If there is more than one monatomic cation of an element , rule 1 is not sufficient , the stock system of nomenclature names the cations after the element as in rule 1 but follows this by a roman numeral in parentheses denoting the charge on the ion. Example Fe2+ is called iron (ll) ion and Fe3+ is called iron (lll) ion. In an older system of nomenclature, ions are named by addng the suffixes -ous and -ic to a stem name of the element to indicate the ions and higher charge ,respectively. Example : Fe2+ is calle ferrous ion , Fe3+ ferric ion

Naming of binary compounds (Ionic compounds)

• name of cation first then anion

• metal atom retains the name of the element , when the element can form cations with different charges , the charge is written as a Roman numeral in brackets

• name of non-metals is changed to end in -ide

• EXAMPLE: CaBr2 is calcium bromide not calcium (ll) bromide or calcium dibromide because calcium can only form the Ca2+ cation an bromine only the Br anion Cr2O3 is chromium (lll) oxide

Molecular (covalent) compounds

Equation

symbolic representation of a chemical reaction in terms of chemical formulas

CN-

cyanide

OH-

hydroxide

C2H3O2-

acetate

CIO4-

perchlorate

CIO3-

chlorate

CIO2-

Chlorite

CIO-

Hypochlorite

NO3-

nitrate

NO2-

nitrite

CO3 minus 2 charge

carbonate

CrO4 -2 charge

chromate

SO4 2- charge

sulfate

SO3 2- charge

sulfite

PO4 -3 charge

phosphate

PO3 -3 charge

phosphite