1.5 Chemical Formulae

Question 1

What is the definition of valency?

Answer 1

Before we do formulae we must learn about a thing called valency.
Valency is the number of bonds that an element can form. The valency of
an element in groups 1 to 8 can be worked out using the periodic table. This means for example that all the alkali metals have a valency of 1 and so on.

Question 2

What is formulae?

Answer 2

The formulae of covalent molecular compounds give the number of
atoms present in the molecule, but in ionic and covalent network
compounds the formulae give the simplest ratio of ions/atoms in the
substance.

A way to work out chemical formula is to use SVSDF.
Eg:

Symbol: C Cl
Valency: 4. 1.
Swap:     1. 4.
Divide:   1. 4. 
Formula: CCl4

Question 3

REMEBER SOMETHING PLEASE!!

Answer 3

You can find ions valency on page 8 of your data booklet! <3

Question 4

How to calculate ionic formulae.

Answer 4

The ionic formula includes the charges on the ions (which is easier than it
sounds!) the charges are the same as the valency for the element or group
ion. Remember that all metals are positively charged and non-metals are
negatively charged.