Structure and Bonding
Halogens
chlorine = green, gas, -34c bp
Bromine = red-brown, liquid, 59c bp
Iodine = dark grey, solid, 185c bp
Gets darker, gas --> solid, bp gets higher, more reactive
Covalent bonding (1)
Sharing pairs of electrons
Diatomic molecules
Triatomic Molecules
Covalent bonding (2)
Properties of simple covalent substances
High melting point = strong bonding
Low melting point = weak bonding
The covalent bonds binding the atoms together are very strong but there are only very weak forces holding the molecules to each other (the intermolecular forces). Therefore, only a low temperature is needed to separate the molecules when they're melted or boiled.
Intermolecular forces = forces between molecules
Intramolecular forces = forces between atoms
Carbon Structures
Allotropes = each of two or more physical forms in which an element can exist.
Graphite, charcoal and diamond are allotropes of carbon
Diamond
A lot of energy is required to separate the atoms. The covalent bonds are strong. This means that more energy is required to break the bonds = high mp and bp
Drill tips, cutting tools
Graphite
A lot of energy is required to separate the atoms. The covalent bonds are strong. This means that more energy is required to break the bonds = high mp and bp
good conductor of electricity = free electrons
Pencils
Bonding in metals
metal + nonmetal --> ionic
nonmetal + nonmetal --> covalent
metal + metal --> metallic