Question

An element X has six electrons in its outer shell and forms a diatomic molecule.

1. Why would that be so? 
2. What kind of bond would it form?
3. Draw the structure of the molecule it would form. 
4. A certain other element Y has two electrons in its second shell. Draw the structure of the molecule that X would form with Y.

Answer 1

• X is oxygen. Its atom needs 2 more electrons to complete its octet, so two oxygen atoms share two electron pairs. This forms O² with a double covalent bond; structure: O=O (Lewis structure: :Ö=Ö:).
• Y, with configuration 2,2, is beryllium. X and Y form BeO, represented ionically as Be²⁺ O²⁻.