Unit 1-Formulae
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What does the ending ‘‑ide’ mean?
The compound contains only the two elements named
What do the endings ‘‑ite’ and ‘‑ate’ mean?
They indicate oxygen is also present
What does a Roman numeral in a name show?
The valency of the element
What do prefixes mono‑, di‑, tri‑, tetra‑ mean?
1, 2, 3, 4 atoms
What is valency?
The combining power of an element (number of bonds it makes)
How do you find valency of elements?
How do you find valency of group ions?
From the data booklet (charge = valency)
Steps to work on chemical formula using valencies.
Symbols → Valencies → Swap → Divide (if possible) → Formula
Why do some metals need Roman numerals?
They can form ions with different valencies
What is the formula of strontium chloride?
SrCl₂
What is the formula of germanium sulfide?
GeS₂
What is the formula of copper(II) chloride?
CuCl₂
What is the formula of copper(I) chloride?
CuCl
What is a group ion?
An ion containing more than one type of atom
Give an example of a group ion
Sulfate SO₄²⁻ Carbonate CO₃²⁻ Hydroxide OH⁻ Nitrate NO₃⁻
How do you write formulae with group ions?
Use valency rules and brackets when needed
What is the formula of magnesium carbonate?
MgCO₃
What is the formula of beryllium phosphate?
Be₃(PO₄)₂
What does the formula of a covalent molecule show?
The number of each type of atom in one molecule
What does the formula of a covalent network show?
The simplest ratio of atoms
What is the formula of carbon dichloride?
CCl₂
What is the formula of phosphorus tetrahydride?
PH₄
What does an ionic formula show?
The simplest ratio of ions in the compound
What must be included in an ionic formula when asked?
Charges on each ion