Magnesium and calcium are in group 2 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2016 - Paper 1

The balanced equation for the reaction between magnesium and steam is:

Calcium is more reactive than magnesium because it has a larger atomic radius and fewer ionization energy barriers to overcome. Calcium has the electronic configuration of 2.8.8.2, while magnesium has 2.8.2. The additional outer shell electron in calcium is further from the nucleus and is therefore less tightly held, making it easier for calcium to lose an electron and react.

To calculate the empirical formula of calcium bromide:

1. Divide the mass of each element by its relative atomic mass:

   • For Calcium: $0.2 g \div 40 g/mol = 0.005 \text{ mol}$
   • For Bromine: $0.8 g \div 80 g/mol = 0.01 \text{ mol}$

2. Find the simplest mole ratio:

   • $\frac{0.005}{0.005} : \frac{0.01}{0.005} = 1 : 2$

3. The empirical formula of calcium bromide is therefore $CaBr_2$.