Question

what element forms an ion with an electronic configuration of $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}$ (or $kr$) and a $-2$ charge? give the symbol for the element.
element symbol:

Explanation:

Step1: Determine the number of electrons in the ion

The electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}\) (or \([Kr]\)) has 36 electrons. Since the ion has a \(- 2\) charge, it has gained 2 electrons.

Step2: Calculate the number of electrons in the neutral atom

Let \(x\) be the number of electrons in the neutral atom. Then \(x+2 = 36\), so \(x=36 - 2=34\).

Step3: Identify the element

The element with 34 electrons (atomic number \(Z = 34\)) is selenium (\(Se\)).

Answer:

\(Se\)