Build the Carbon Atom

Why it matters

Carbon is the backbone of life, yet its nucleus holds a secret balance of six protons and six neutrons. Build this atom to see how its four valence electrons dictate its chemistry.

Predict first

If carbon has an atomic number of 6 and a mass number of 12, how many neutrons are in its nucleus?

Mass number (12) minus atomic number (6) equals 6 neutrons.

• 6 neutrons — correct
• 0 neutrons
• 12 neutrons

What you do

Build a neutral carbon-12 atom: 6 protons and 6 neutrons in the nucleus, then add 6 electrons and watch them fill the shells (2, then 4).

Check yourself

Why does carbon typically form four covalent bonds?

Carbon's electron configuration is 2,4. It needs 4 more electrons to complete its octet, so it shares 4 valence electrons.

What is the charge of the nucleus in a neutral carbon atom?

The nucleus contains 6 protons (+6) and 6 neutrons (0), resulting in a nuclear charge of +6.

• It has 4 valence electrons to share — correct
• It has 6 protons in the nucleus
• It wants to lose all 6 electrons
• It has 2 electrons in the outer shell
• +6 — correct
• 0
• +12