A gold atom is heavier than an iron atom; $1 \mathrm{mg}$ of which element - gold or iron - will contain a greater number of atoms? 

Fill up the blank spaces in the following table.

Fill up the blank spaces in the following table.

Construct the formulae of the compounds using above table.

In the following table a $\text{'}-\text{'}$ represents a shared electron pair. Let us find out the similarities among the various entries in the table and have a grasp of the whole thing.