Formulae Of Elements And Compounds Flashcards
How to find the formulae of non metals in group 0 (the noble gases)
The formula = the chemical symbol
Eg, Heliums formulae = He
How to find the formulae of group 7 / 17 non metals
Group 7 formulae = chemical symbol ₂
So chlorine = Cl ₂
Atoms which naturally form with 2 of themselves are called
diatomic particles, most diatomic particles are found in group 7
Other diatomic particles include
- oxygen
- nitrogen
- hydrogen
Phosphorus
Exists as simple covalent molecules with 4 phosphorus atoms, so it’s written as P₄
All other non metals
Exist as giant structures, meaning that the number of particles cannot be counted
Their formula is their chemical symbol.
Sulphur
Exists as a simple molecules (not a giant structure) of 8 atoms.
Metals formulae
Exist as giant metallic lattices
Formula = empirical formula (chemical symbol)
Name of simple covalent compounds
Formed from 2 Or more non metals
Simple molecules consisting of a fixed number of different atoms covalently bonded
Eg hydrogen chloride
The formulae of simple covalent molecules show
- each element in the molecule
- number of each atoms in the molecule
Eg hydrogen chloride = HCl
Formula of giant covalent compounds
formed from two or more nonmetals
Giant lattice of covalently bonded atoms
Eg Diamond = C
How to write the formula of giant covalent compounds
- write the ratio of the numbers of each atom (empirical formula)
- eg, silicon dioxide = SiO₂
Hydrogen ions formulae
NORMALLY have a plus on charge
H⁺
Metal ions have
- positive charge
- their charges are the same as the group number (column) that they are in
- eg group three has +3 charge
Transition metal (groups 3-12) ions have
- positive ions
- usually a plus two charge
- SOMETIMES can form an ion with a different charge
- silver ALWAYS has has 1+ charge
- Iron is ALWAYS EITHER 2+ or 3+ charge
