Practice portal › Nuclei › Composition and Size of the Nucleus

How many protons, neutrons and nucleons respectively present in the nucleus of ²⁰⁶₈₂Pb.

Asked in GSEB Board July 2016 · Composition, isotopes and isobars

• (1) 206, 82, 288
• (2) 82, 206, 288
• (3) 82, 124, 206
• (4) 124, 82, 206

Step-by-step solution

Why the other options are wrong

• (1) This reads the mass number 206 as the proton count and then adds the two numbers: 206+82=288. Nothing is added — the mass number 206 is already the nucleon count.
• (2) Here the mass number is used as the neutron count and again added on. Neutrons are what is left when the protons are taken out: 206-82=124.
• (4) The right three numbers in the wrong order: 124, 82, 206 is neutrons, protons, nucleons, and this question asks for the protons first.

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.