Question

use the periodic table to determine the electron configuration for zinc (zn) and technetium (tc) in noble - gas notation.
zn:
✓ $ar4s^{2}3d^{10}$
× $ne3s^{2}3p^{6}4s^{2}3d^{10}$
× $ar4s^{2}3d^{9}$
$ar4s^{2}4d^{10}$
tc:
$ar4s^{2}3d^{10}4p^{6}5s^{2}4d^{6}$
$kr5s^{2}4d^{6}$
$kr5s^{2}4d^{5}$
$kr5s^{2}5d^{6}$

Explanation:

Step1: Determine the noble - gas core for Zn

Zinc (Zn) has an atomic number of 30. The noble gas before Zn is Argon (Ar) with an atomic number of 18.

Step2: Determine the remaining electrons for Zn

The remaining number of electrons is \(30 - 18=12\). The electron configuration after Ar is \(4s^{2}3d^{10}\). So the electron configuration of Zn is \([Ar]4s^{2}3d^{10}\)

Step3: Determine the noble - gas core for Tc

Technetium (Tc) has an atomic number of 43. The noble gas before Tc is Krypton (Kr) with an atomic number of 36.

Step4: Determine the remaining electrons for Tc

The remaining number of electrons is \(43 - 36 = 7\). The electron configuration after Kr is \(5s^{2}4d^{5}\) (because for transition metals, the \(ns\) orbital is filled before the \((n - 1)d\) orbital and there is a half - filled stability consideration in some cases, but for Tc, following the Aufbau principle: after filling \(5s\) with 2 electrons, we fill \(4d\) with 5 electrons)

Answer:

Zn: \([Ar]4s^{2}3d^{10}\)
Tc: \([Kr]5s^{2}4d^{5}\)