Question

1. why does an anion of p³⁻ have a larger radius than a neutral atom of p?

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Explanation:

A neutral phosphorus (P) atom has an atomic number of 15, so its electron configuration is \(1s^2 2s^2 2p^6 3s^2 3p^3\), with 15 protons and 15 electrons. The \(P^{3 -}\) anion is formed when a P atom gains 3 electrons, resulting in an electron configuration of \(1s^2 2s^2 2p^6 3s^2 3p^6\), so it has 15 protons but 18 electrons. The number of protons (positive charge) remains the same, but the number of electrons (negative charge) increases. The increased number of electrons leads to greater electron - electron repulsion within the electron cloud. Since the protons' positive charge has to pull on more electrons, the electron cloud expands. This expansion of the electron cloud results in a larger atomic radius for the \(P^{3 -}\) anion compared to the neutral P atom.

Answer:

A neutral P atom has 15 protons and 15 electrons. The \(P^{3-}\) anion has 15 protons but 18 electrons. The same nuclear charge (from 15 protons) acts on more electrons (18 vs. 15), causing greater electron - electron repulsion and an expanded electron cloud, so \(P^{3-}\) has a larger radius.