In covalent bonding, the number of covalent bonds that can be formed is determined by what?

• A. The total number of protons in the nucleus
• B. The number of valence electrons, which indicates how many covalent bonds can be formed
• C. The total number of electrons in the atom
• D. The ionization energy

Answer: (B)

Covalent bonds are formed when atoms share electrons to obtain a stable electron arrangement around each atom, usually aiming for a full valence shell. The number of covalent bonds an atom can form is determined by its valence electrons—the electrons available to be shared. Since each covalent bond typically uses one electron from the atom (paired with one from another atom), the atom’s bonding capacity matches how many electrons it needs to complete its outer shell. For common main-group elements this means carbon, with four valence electrons, can form about four bonds; nitrogen, three; oxygen, two; hydrogen, one. Ionization energy or the total number of electrons or protons in the nucleus doesn’t set this bonding count—the bonding capacity is tied to valence electrons. There are occasional exceptions (like expanded octets for some elements), but the general rule is determined by valence electrons.