Ionic Bonds

Ions are atoms that have become charged by gaining or losing electrons.

Cations are positively charge ions (metals).

Anions are negatively charged ions (nonmetals).

Ions Review

Oxidation number: The number of electrons an atom needs to gain, lose or share to become stable. For elements that form ions the oxidation number is the charge of the ion it will form.

Elements in the same group have the same oxidation number.

Oxidation Numbers

+1 0

H +2 +3 -4 -3 -2 -1 He

Li Be B C N O F Ne

NaMg

Al Si P S Cl Ar

Oxidation Numbers

Ions are written by writing the charge of the ion as a superscript after the symbol for the element.

Cations: Na+1 Mg+2

Anions: Br-1 N-3

Ions

Ionic bond: bonds that form between a metal and nonmetal –or- a bond that forms between a cation and a anion.

One atom loses electrons and becomes a cation, another atom gains those electrons and becomes an anion.

The two atoms are attracted to each other because of their opposite charges.

Ionic Bonds

Ionic Bonds

P – 6N - 8P – 6N - 8P – 6N - 8Be

P – 6N - 8P – 6N - 8P – 6N - 8Se

An ionic bond is the force of attraction between cations and anions that holds ionic compounds together.

Ionic bonds form when an atom gains or loses electrons.

Ionic Bonds

We draw ionic bonds by showing the movement of electrons on Lewis dot diagrams.

Be S

Ionic Bonds

An ionic compound is a compound that is made of ions and is held together by ionic bonds.

A binary ionic compound has only two elements.

The charges on all the ions in an ionic compound add up to zero. An ionic compound is neutral.

****This means the oxidation numbers also add up to zero.

Ionic Compounds

If the oxidation numbers on the two elements is different then there will be more of one element than the other.

Ionic Compounds

If we know which elements are in a binary ionic compound then we can figure out what the formula for the compound is.

We just need to figure out the ratio that results in a net charge of zero.

Formulas of Ionic Compounds

FormulasExample: Magnesium + Chlorine

1.

2.

3.

4.

Four steps:

1. Note the oxidation numbers of the ions

2. Write the symbol of the positive ion

3. Write the symbol of the negative ion

4. Use subscripts to get a total oxidation number of zero

FormulasPractice:

Potassium + nitrogen

1.

2.

3.

4.

Four steps:

1. Note the oxidation numbers of the ions

2. Write the symbol of the positive ion

3. Write the symbol of the negative ion

4. Use subscripts to get a total oxidation number of zero

Formulas

Practice: Beryllium + phosphorous

1.

2.

3.

4.

Four steps:

1. Note the oxidation numbers of the ions

2. Write the symbol of the positive ion

3. Write the symbol of the negative ion

4. Use subscripts to get a total oxidation number of zero