Given a carbon atom with four single bonds ($C_4$), how many hydrogen atoms ($H_{\mathrm{n}}$) can be attached to it if it is not bonded to any other atoms besides hydrogen?

• A. $2$
• B. $1$
• C. $3$
• D. $4$

Answer: (D)

Verified step by step guidance

1. Recall that a carbon atom typically forms four covalent bonds to satisfy the octet rule, meaning it needs a total of four bonds to be stable.
2. Since the carbon atom in question is not bonded to any other atoms besides hydrogen, all four of its bonds must be with hydrogen atoms.
3. Each hydrogen atom forms one single bond, so the number of hydrogen atoms attached to the carbon equals the number of bonds carbon can form.
4. Therefore, the carbon atom can have four hydrogen atoms attached to it, making the molecular formula CH₄ (methane).
5. This satisfies the valency of carbon and ensures all atoms have full outer electron shells.