Answer: D (³⁷₁₇R, a neutral atom). Start from the isotope \({}^{32}_{16}\text{Q}\): it has 16 protons, \(32 - 16 = 16\) neutrons and, being a neutral atom, 16 electrons.
Particle R has four more neutrons, one more proton and one more electron than this isotope. So R has \(16 + 4 = 20\) neutrons, \(16 + 1 = 17\) protons and \(16 + 1 = 17\) electrons.
Because the number of protons (17) equals the number of electrons (17), R carries no overall charge — it is a neutral atom, not an ion, so any option with a negative charge is wrong. The nucleon number is protons plus neutrons, \(17 + 20 = 37\), and the proton number is 17, giving \({}^{37}_{17}\text{R}\). The common error is to forget that gaining an extra proton and an extra electron together keeps the particle neutral.
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