Question

which element has the electron configuration 1s²2s²2p⁶3s²3p⁵?
phosphorus
iron
chlorine
sulphur

Explanation:

To determine the element, we count the total number of electrons. For the electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}\), we sum the exponents: \(2 + 2+6 + 2+5=17\). The number of electrons in a neutral atom is equal to its atomic number. Chlorine (\(Cl\)) has an atomic number of \(17\). Phosphorus (\(P\)) has an atomic number of \(15\) (\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{3}\)), iron (\(Fe\)) has an atomic number of \(26\), and sulphur (\(S\)) has an atomic number of \(16\) (\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}\)).

Answer:

chlorine