Lesson 3: Ionic compounds

Question 1

How do you write an ionic compound when given the ions?

Answer 1

• You have to make sure the charge cancels out to 0 by increasing atoms.

Question 2

What is the chemical formula for Magnesium Hydroxide:
Mg²⁺ OH⁻

Answer 2

• You have 2 positives
• You need 2 negatives
  So you write: Mg(OH)₂

Question 3

What is the chemical formula for Aluminium carbonate:
Al³⁺ + CO₃²⁻

Answer 3

• You need 6p’s and 6n’s
• So, you write: Al₂(CO₃)₃

Question 4

What is the difference between: (CO₃)₃ and CO₉?

Answer 4

• (CO₃)₃ means three lots of CO₃. 3 carb, 9 oxygen
• Whereas, CO₉ is a different compound. 1 carb, 9 oxygen