Question

20/23
what atom matches this electron configuration?
xe6s²4f¹⁴5d⁹
gold
platinum
mercury
thallium

Explanation:

Step1: Determine the atomic number from the electron configuration

The electron configuration \([Xe]6s^{2}4f^{14}5d^{9}\) means we need to add the electrons from \(Xe\) (atomic number \(54\)) plus \(2 + 14+9\) electrons. So \(54 + 2+14 + 9=79\). But wait, for transition - metals, there are some exceptions. For \(5d\) and \(4f\) electrons, the actual electron - filling can have some rearrangements. The general formula for the atomic number \(Z\) of an element with electron configuration \([Xe]6s^{n}4f^{m}5d^{k}\) is \(Z = 54 + n + m + k\). Here \(n = 2\), \(m = 14\), \(k = 9\), so \(Z=54 + 2+14 + 9 = 79\) (but we need to check for electron - pair stability).

Step2: Check the electron - pair stability for \(5d\) orbitals

Platinum (\(Pt\)) has an electron configuration of \([Xe]6s^{1}4f^{14}5d^{9}\) (due to the stability of half - filled and fully - filled sub - shells. The \(6s\) electron can move to the \(5d\) orbital to get a more stable configuration). Gold (\(Au\)) has \([Xe]6s^{1}4f^{14}5d^{10}\), mercury (\(Hg\)) has \([Xe]6s^{2}4f^{14}5d^{10}\), and thallium (\(Tl\)) has \([Xe]6s^{2}4f^{14}5d^{10}6p^{1}\). Considering the \(5d\) electron count and the electron - pairing rules for stability (a \(5d^{9}\) configuration with a \(6s^{1}\) contribution, which is characteristic of platinum's electron - configuration deviation from the simple \(n + l\) rule).

Answer:

B. Platinum