Ionic Nomenclature

An ionic bond forms between metals and nonmetals.

Metals Nonmetals

Because nonmetals tend to have high electronegativity, they are strongly attracted to the electrons of other atoms. Because metals tend to have low effective nuclear charge, they cannot hold on to their valence (outermost) electrons tightly.

Metals Nonmetals

Nonmetals can pull on the electrons of metals harder than the metals themselves can, so electrons get transferred from the metal to the nonmetal.

Na Cl

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Na has 11p+ and 11e-Cl has 17p+ and 17e-

Nonmetals can pull on the electrons of metals harder than the metals themselves can, so electrons get transferred from the metal to the nonmetal.

ClNa

NOW Na has 11p+ and 10e-

NOW Cl has 17p+ and 18e-

After the transfer of electrons, the metal ends up with a positive charge (lost negatives) and the nonmetal ends up with a negative charge (gained negatives). Charged atoms are called ions; the positive ones are called cations and the negative ones are called anions.

Cl-Na+

NOW Na+ has 11p+ and 10e-

NOW Cl- has 17p+ and 18e-

Like magnets, the positive metal wants to stick to the negative nonmetal, and an ionic bond is formed.

Na+ Cl-

Ionic compounds often form crystal shapes as positive metals want to be surrounded by negative nonmetals, and vice versa. NaCl (table salt) has a cube shape for this reason.

When metal atoms lose electrons, they will lose enough valence electrons to because like a previous noble gas.

Na Na = 11e- = [Ne]3s1

Na+ Na+ = 10e- = [Ne]3s0 or Ne

When nonmetals gain electrons, they will gain enough valence electrons to become like the next noble gas.

Cl

Cl-

Cl = 17e- = [Ne]3s23p5

Cl- = 18e- = [Ne]3s23p6 or Ar

This gives us a trend for the charges elements will have, as metals will have enough positive charge to be like the previous noble gas and the nonmetals will have enough negative charge to be like the next noble gas.

When metals and nonmetals get together, they do so in such amounts that the resulting compound is neutral (has zero charge). This is easy to figure out if the charges are the same in number, for example:

Na+ and Cl- make NaCl

Mg+2 and S-2 make MgS

Al+3 and N-3 make AlN

Save time – don’t write “1”

When the numbers don’t match, the atoms will still get together in the right amounts to make the resulting compound neutral:

Al+3 and S-2 total +1 so more S-2 is needed

When the numbers don’t match, the atoms will still get together in the right amounts to make the resulting compound neutral:

Al+3 and S-2

S-2 total -1, so more Al+3 is needed

When the numbers don’t match, the atoms will still get together in the right amounts to make the resulting compound neutral:

Al+3 and S-2

Al+3 S-2 total +2, so more S-2 is needed

When the numbers don’t match, the atoms will still get together in the right amounts to make the resulting compound neutral:

Al+3 and S-2

Al+3 S-2

S-2

Now the compound is neutral, so the result is Al2S3

This method will work each time, but there is a short cut. Notice:

Al+3 and S-2

Al2S3

But if you use the crisscross method, don’t forget to reduce if possible! (Save time, don’t write “1”)

Al+3 and N-3

Al3N3 = AlNAlways write the metal first!

To name an ionic compound with only representative elements (ones in the tall columns), name the metal and then name the nonmetal – changing the ending to “ide”.

Examples: LiF = lithium fluoride CaBr2 = calcium bromide

Notice the subscripts have no affect on the names.

Polyatomic ions are groups of elements (poly = many) that are covalently bonded together and have an overall ionic charge.

When forming a compound, polyatomic ions work as a group. So after criss-crossing the charges, it will be necessary to use parentheses if the subscript is bigger than 1.

Examples: Lithium and Arsenate Li+ and AsO4 -3

Li3AsO4

Beryllium and ArsenateBe+2 and AsO4 -3

Be3(AsO4)2

The 4 is not changed!

The 4 is not changed!

When naming ionic compounds with polyatomic ions, the polyatomic ion already has a special name that never changes.

Examples: LiC2H3O2 = lithium acetate NH4OH = ammonium hydroxide

If the ending is a normal nonmetal, still change the ending to “ide”!

There are some metals that can lose more than just one amount of electrons. Most of these metals are transition metals, but also some of the metals directly below the stairstep line do this.

Because there is more than one possible positive charge for these metals, a way of naming them is needed to specify which charge it has.

The old system of naming (Classic System) uses suffixes of -ous and -ic to distinguish the charges. Sometime the Latin name of the element is used before changing the ending to -ous or -ic.

Cobalt +2 Cobaltous+3 Cobaltic

Copper +1 Cuprous+2 Cupric

 Gold +1 Aurous

+3 Auric Iron +2 Ferrous

+3 Ferric

The new system (Stock system) uses the normal name for the metal and then added a roman numeral in parentheses to stand for the charge.

Chromium +2 Chromium (II)+3 Chromium (III)+6 Chromium (VI)

   Gold +1 Gold (I)

+3 Gold (III) Manganese +2 Manganese (II)

+3 Manganese (III)+4 Manganese (IV)+7 Manganese (VII)

When naming an ionic compound with a metal that can have more than one charge, the nonmetal’s charge will tell you how much positive charge the metal must have. The nonmetal still ends in “ide”.FeO Fe2O3

 Oxygen must have a -2 charge Oxygen must have a -2 chargeThere is 1 oxygen There are three oxygensThe total negative charge is -2 The total negative charge is -6 The total positive charge must be +2 The total positive charge must be +6There is 1 iron There are two ironsThus the iron has a +2 charge Thus each iron has a +3 charge

(+2 / 1 = +2) (+6 / 2 = +3)

This is Iron(II) Oxide or This is Iron(III) Oxide or Ferrous Oxide Ferric Oxide