Chemistry 5072Chemistry 5072

Dot-and-cross diagramDot-and-cross diagram

Ionic bondingIonic bondingHence the ionic bond is an electrostatic forceHence the ionic bond is an electrostatic force

Ionic bondingIonic bonding Ionic bonds are formed between atoms of metals

and atoms of non-metals, as a result of the transfer of electrons.

Compounds formed by ionic bonding are called ionic compounds. Metals react with non-metals to form ionic compounds.

Note : The particles present in ionic compounds are ions; there are NO molecules in ionic compounds.

Ionic bonds are formed between atoms of metals and atoms of non-metals, as a result of the transfer of electrons.

Compounds formed by ionic bonding are called ionic compounds. Metals react with non-metals to form ionic compounds.

Note : The particles present in ionic compounds are ions; there are NO molecules in ionic compounds.

More Practice1. Draw ‘dot and cross’ digrams to show the formation of :

Calcium oxide

Magnesium chloride

Sodium oxide

2. Draw ‘dot and cross’ diagram to show the bonding in

O atom 2,6

Ca2+ ion O2- ion Ionic bond(electrostatic force)

x xx

xx

x x

xx

xx

x

x

xxx

xx

xx

Ca atom 2,8,8,2

Calciumoxide(CaO)

2+

x

2-x

xxxx

xx

xx

xxxx

xx

xx

xx

2,8,8 2,8

transfer of 1 electron

transfer of 1 electron

O atom 2,6

Ca2+ ion O2- ion Ionic bond(electrostatic force)

x

x

Ca atom2,8,8,2

Calciumoxide(CaO)

2+

x

2-x

xx

xx

xx

xx

2,8,82,8

transfer of 1 electron

transfer of 1 electron

O

O

Ca

Ca

Note: onlyvalence shellsare shown

2,8,2

x xx

xx

x

x

xx

x2,8,7

x x

x

2 Cl¯ ions

¯

Mg2+ ion

x x xx

x

xx

x

xx

2+

MagnesiumchlorideMgCl2

transfer of 1 electron

transfer of 1 electron

2,8 2,8,8

2

Mg atom

Cl atoms

2,8,2

x

x2,8,7

x

2 Cl¯ ions

¯

Mg2+ ion

xx

x

xx

x

xx

2+

MagnesiumchlorideMgCl2

transfer of 1 electron

transfer of 1 electron

2,8 2,8,8

2

Mg atom

Cl atoms

Note: onlyvalence shellsare shown

Mg

Mg

Cl

Cl

Cl

Chemical formulae of ionic compoundsChemical formulae of ionic compounds

An easy method of writing a chemical formula involving 2 ions is to ‘criss-cross’ the charges

An easy method of writing a chemical formula involving 2 ions is to ‘criss-cross’ the charges

Eg. Write the formula of aluminium oxide.

Ions: Al3+ O2-

Eg. Write the formula of aluminium oxide.

Ions: Al3+ O2-

Chemical formula: Al2O3

Check that the total positive charge and total negative charge are equal

Chemical formula: Al2O3

Check that the total positive charge and total negative charge are equal

Chemical formulae of ionic compoundsChemical formulae of ionic compounds

Write the formula of magnesium carbonate.

Ions: Mg2+ CO3 2-

Chemical formula: MgCO3

Check that the total charges are balanced.

Write the formula of magnesium carbonate.

Ions: Mg2+ CO3 2-

Chemical formula: MgCO3

Check that the total charges are balanced.

All subscripts are in the simplest set of whole

numbers

Chemical formulae of ionic compoundsChemical formulae of ionic compoundsWrite the formula of calcium nitrate.

Ions: Ca2+ NO3 -

Write the formula of calcium nitrate.

Ions: Ca2+ NO3 -

a) subscript ‘1’ is not written

b) Polyatomic ions should be written within brackets if there is a subscript attached

Chemical formula: Ca(NO3)2

Check that the total charges are balanced.

Properties of ionic compoundsProperties of ionic compounds

High melting and boiling points Usually soluble in water Low volatility Conducts electricity only in molten or

aqueous state

Physical properties: