1.40 explain, using dot and cross diagrams, the formation of covalent compounds by electron sharing
To draw a dot and cross diagram for a covalent bond, you need to draw the outer shells of the two atoms involved with an overlap, in this overlap should be the electrons they share. Half the electrons in the overlap should be dots and half crosses, because one electron in every pair comes from each atom. The rest of the electrons for the outer shell should be drawn on, one atom with dots, the other with crosses.
For example, H + Cl = HCl:
You need to be able to do dot and cross for
the following substances (comment if you need help with any):