2.5 - Covalent Bonding

What does covalent bonding exist between

non-metals atoms only

What happens in covalent bonding

atoms share electrons to form molecules and to achieve a noble gas configuration

Define covalent bond

Result of attraction between the bonding pair of electrons (negative charge) and the nuclei (positive charge) of all the atoms involved

What are the types of covalent bonds

• Single bond - 1 pair of electrons

• Double bond - 2 pairs of electrons

• Triple bond - 3 pairs of electrons

In covalent bonding dot-cross diagrams, should you show all shells

No, only outer shell

When naming chemical formulae you need prefixes, name them

1 - mono (only used when there are molecules that are simmilar

2 - di

3 - tri

4 - tetra

5 - penta

6 - hexa

Also note: last element takes -ide

Explain the simple molecular structure of covalent compounds

• Most covalent compounds are made up of simple molecules

• Between different molecules there are weak forces of attraction called intermolecular forces

• These are weak and easy to break

• But within each molecule, the atoms are held together by strong covalent bonds which are called intramolecular bonds

• These are strong and hard to break

Name four properties of covalent compounds

• Gases or solids at RTP

• Have low melting and boiling points at RTP → due to weak forces of attraction between the molecules (intermolecular forces) which require little energy to break

• do not dissolve in water but dissolve very easily in organic solvents

• do not conduct electricity since they do not have free electrons (like metals) or free ions (like solutions of salt in water) o

What is diffusion

The passive movement of particles from a region of high concentration to a region of low concentration down a concentration gradient until equilibrium is reached

What factors affect diffusion

• Temperature

• Pressure

• Molecular mass

Explain how molecular mass affects diffusion

The lower the relative molecular mass of the gas, the faster the gas will diffuse

Explain how

• The particles are packed

• Moving around

• Densities

In solids, liquids and gases

• Solids most tightly packed, gases least

• Solids can only vibrate to a from a fixed position, liquids particles can move around each other, in gases particles can move at high speeds

• Density highest in solids, lowest in gases