Ionic Compounds and Metals

Chapter 7

Ions are charged atoms. An neutral atom becomes an ion when it

either gains or loses electrons. The imbalance between the number of

protons and the number of electrons results in a charge on the atom.

An ion with a positive charge is called a cation.

An ion with a negative charge is called an anion.

Ion Formation

The octet rule states that atoms tend to lose, gain, or share electrons in order to acquire a full set of eight valence electrons.

The Octet Rule

The electrostatic force that holds two ions together is called an ionic bonds.

compounds that contain ionic bonds are called ionic compounds.

Na + Cl Na+ + Cl-

[Ne] 3s1 + [Ne] 3s23p5 [Ne] + [Ar]

Formation of Ionic Bonds

Most ionic compounds have a crystal like structure.

This structure is known as a crystal lattice.

Structure of Ionic Compounds

When ionic compounds are dissolved in water they break apart into a cation and an anion.

Not all ionic compounds dissolve in water.

Ones that do are called electrolytes.

Dissolved Ionic Compounds

The chemical formula for an ionic compound, called a formula unit, represents the simplest ratio of ions involved.

MgCl2

A monatomic ion is a one-atom ion.

Names and Formulas of Ionic Compounds

Representative elements of the same groups usually have the same ionic charges.

Group 1: H+, Li+, Na+

Group 2: Be2+, Mg2+, Ca2+

Group 15: N3-, P3-, As3-

Group 16: O2-, S2-, Se2-

Group 17: F-, Cl-, Br-

Transition elements can usually have more than one charge. Example Fe2+ and Fe3+

Common Ions and their charges

Most transition metals can have a few different charges.

Example: Fe2+, Fe3+

Fe2O3

FeO

Transition Metal Ions

Polyatomic ions are ions that are made up of more than one atom.

There are a few you need to memorize….sorry. Ammonium: NH4

+

Nitrite: NO2-

Nitrate: NO3-

Hydroxide: OH-

Hypochlorite: ClO-

Polyatomic Ions

Chlorite: ClO2-

Chlorate: ClO3-

Perchlorate: ClO4-

Carbonate: CO32-

Sulfite: SO32-

Sulfate: SO42-

Peroxide: O22-

PO43-

The cation comes first in the name then the anion. If the anion is a monatomic ion we give it the ending –ide.

NaCl – Sodium Chloride When the formula unit contains two or more of the

same polyatomic ion we put it in parentheses with a subscript to show how many ions are present.

Ba(NO3)2 – Barium Nitrate If the cation is a transition element the charge of

the cation is written as roman numerals in parentheses.

Co(SO4) – Cobalt (II) Sulfate

Naming Ionic Compounds

NH4Cl

Fe(NO3)3

TiBr3

Pb(SO4)2

Chromium (VI) Phosphate

Tin (II) Nitrate

Cobalt (III) Oxide

Chromium (III) Hydroxide

Practice