An atom's maximum number of covalent bonds is determined by the number of valence electrons it has. For instance:

1. Hydrogen: It has one valence electron and can only form one covalent bond.

2. Carbon: It has four valence electrons and can form four covalent bonds—one with each valence electron.

3. Nitrogen: With five valence electrons, nitrogen forms three covalent bonds.

4. Oxygen: It can form two covalent bonds using its six valence electrons.

The bonding capacity of an atom also depends on its group number in the periodic table. Atoms in the same group tend to have the same number of valence electrons and thus form the same number of covalent bonds.