Learn to write and interpret chemical symbols, formulae, and simple chemical equations.
Valency is the combining power of an element. Chemical formulae are written using the valencies of the combining elements.
If hydrogen has valency 1 and oxygen has valency 2, what is the formula for water?
H₂O (two hydrogens combine with one oxygen to balance valencies)
What does the formula NaCl represent?
Sodium chloride (common salt), with one sodium atom bonded to one chlorine atom
A chemical equation shows reactants transforming into products, and must be balanced so the number of atoms is equal on both sides.
Write a word equation for hydrogen burning in oxygen to form water.
Hydrogen + Oxygen → Water
Why must a chemical equation be balanced?
Because atoms are neither created nor destroyed in a reaction, so the same number of each type of atom must appear on both sides
1. What is valency?
2. What does the formula CO₂ tell you about its composition?
3. Write the word equation for carbon burning in oxygen to form carbon dioxide.
4. Why must chemical equations be balanced?
5. What is the chemical formula for common salt?