What are the two types of bonding and what is the difference between them?

One example of covalent bonding is the molecule Cl2. Another is H20 either use a diagram or in words explain the covalent bonding between the hydrogen and oxygen.

What are the properties of simple covalently bonded molecules?

If an element is in group 7 then how many electrons does it have in its outer shell and where can you find a group in the periodic table?

What do periods tell us and how do you find a period in the periodic table?

What did Johann Dobereiner do in the discovery of the periodic table?

What did Demitri Mendelev do in the discovery of the periodic table?