Answer: Atomic number.
- A Mass number
- B Atomic number
- C Neutron number
- D Molar mass
Correct answer: B. Atomic number
Explanation: Z represents atomic number, which is the number of protons.
Bohr's model: electrons occupy fixed circular shells (K, L, M) around the nucleus, with each shell holding up to 2n2 electrons.
Concept context
Explore how electrons are arranged inside an atom. Covers Bohr's model, quantum numbers, Heisenberg's uncertainty principle, shapes of s, p, d orbitals, and electronic configuration rules.