Compounds and Bonding

Covalent Bonding

Covalent bonds form between atoms of non-metallic elements.

In a covalent bond, the octet rule is satisfied by atoms sharing electrons so that each can have a full outer valence shell.

Shared pair of electrons forms covalent bond between hydrogen and oxygen in this water molecule

The number of electrons required to fill the outer shell indicates how many covalent bonds an atom can form. For example, to satisfy the octet rule . .

Carbon will form 4 covalent bonds Nitrogen will form 3 covalent bonds Oxygen will form 2 covalent bonds Fluorine will form 1 covalent bonds

Neon will form 0 covalent bonds

We know chlorine gas is a diatomic molecule and has the formula Cl2. A molecule of chlorine gas consists of two atoms held together by a covalent bond.

Chlorine has 7 valence electrons, and requires one more to complete the outer shell

ClCl ClCl

Shared pair of electrons(single covalent bond)

Try these examples. Use dot and cross diagrams to show the covalent bonding in:

HCl (hydrochloric acid) CH4 (methane)

Start with the Lewis dot diagrams for each element involved. Combine the diagrams to form the molecule.

sharing

Try these examples. Use dot and cross diagrams to show the covalent bonding in:

HCl (hydrochloric acid) CH4 (methane)

In a covalent bond, the shared electrons are counted in both atoms valence shells when applying the octet rule.

Simplified

HCl (hydrochloric acid)

Lewis dot structures of molecules show all the bonds (the valence electrons)

CH4 (methane)

Multiple covalent bonds

Atoms joined by covalent bonds can share more than one pair of electrons. Consider a molecule of oxygen O2

Multiple covalent bonds

Two shared pairs = ONE double covalent bond

Try to draw the covalent bonding in CO2

Try to draw the covalent bonding in N2

Three shared pairs = ONE triple covalent bond

Complete the bonding and naming worksheets

Polyatomic ions

Polyatomic ions are groups of atoms held together by covalent bonds but have an overall electrical charge

-1for example

the nitrate ion

NO3-1

CuCl

Copper I chloride

Ca(NO3)2

Calcium nitrate

?

?

(NH4)2CO3

Ammoniumcarbonate

?

Complete the polyatomic ion worksheet

Properties of Covalent CompoundsPhysicalProperty

IonicCrystal

CovalentMolecular

Melting and boiling points

Very highStrong attractions

between ions

Solubility in water

Most ionic compounds are soluble in water.

Conduct electricity

Yes when dissolved in water

or melted

Hardness Very brittle

Structure

Solids with geometrical

arrangement of ions

Properties of Covalent CompoundsPhysicalProperty

IonicCrystal

CovalentMolecular

Melting and boiling points

Very highStrong attractions

between ions

LowWeak attractions

between molecules

Solubility in water

Most ionic compounds are soluble in water.

Only polar molecules

dissolve in water.

Conduct electricity

Yes when dissolved in water

or meltedDo not conduct

Hardness Very brittle Not brittle

Structure

Solids with geometrical

arrangement of ions

Solid, liquid, gas made of

molecules