The atomic number of two elements A and B are 12 and 8 respectively. What type of a compound is formed when they combine?

When elements A and B combine, they will form a compound based on the difference in their atomic numbers.

Step 1: Identify the atomic numbers Element A has an atomic number of 12, which corresponds to Magnesium (Mg). Element B has an atomic number of 8, which corresponds to Oxygen (O).

Step 2: Determine the type of bond The difference in atomic numbers (or more accurately, the difference in electronegativity) determines the type of bond that will form. Magnesium is a metal and Oxygen is a non-metal. When a metal and a non-metal combine, they typically form an ionic bond.

Step 3: Determine the formula of the compound Magnesium has 2 valence electrons it wants to give away, and Oxygen has 6 valence electrons but wants 8. Therefore, one Magnesium atom will give its 2 electrons to one Oxygen atom, forming the compound MgO.

Step 4: Determine the type of compound MgO is an ionic compound because it is formed from a metal (Magnesium) and a non-metal (Oxygen) through an ionic bond.

So, when elements A and B with atomic numbers 12 and 8 respectively combine, they form an ionic compound.