Isotopes and Isobars MCQs

Q1. A laboratory vial is labelled as the isotope hydrogen-1; how many neutrons are packed inside one such nucleus?

• A.2
• B.0
• C.3
• D.1

Answer: B. 0

hydrogen has atomic number Z = 1, so every hydrogen atom has 1 protons. The tag hydrogen-1 sets the mass number A = 1. Neutrons = A - Z = 1 - 1 = 0.

Q2. The periodic-table poster in a classroom shows an entry written carbon-12; what number of neutrons does this atom hold?

• A.18
• B.12
• C.13
• D.6

Answer: D. 6

carbon has atomic number Z = 6, so every carbon atom has 6 protons. The tag carbon-12 sets the mass number A = 12. Neutrons = A - Z = 12 - 6 = 6.

Q3. A museum card describes a single atom of oxygen-16; how many uncharged particles lie in its core?

• A.17
• B.8
• C.24
• D.16

Answer: B. 8

oxygen has atomic number Z = 8, so every oxygen atom has 8 protons. The tag oxygen-16 sets the mass number A = 16. Neutrons = A - Z = 16 - 8 = 8.