Question

1. complete table 2 below. 2

table 2: electron configurations for selected elements
mg
fe
cu
br

Explanation:

Mg

Shorthand

• The noble gas before Mg is Ne.
• So the shorthand is $[Ne]3s^{2}$.

Last Subshell

• The last subshell is $3s$.

Valence Rule

• Mg is a main - group element. So the valence rule is Main - group.

Fe

Spectroscopic (Full)

• Ar has 18 electrons.
• $[Ar]4s^{2}3d^{6}$ means total electrons \(18 + 2+6=26\).
• The full electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}\).

Valence Rule

• Fe is a transition metal. So the valence rule is Transition.

Cu

Last Subshell

• The last subshell is \(3d\).

Br

Spectroscopic (Full)

• Ar has 18 electrons.
• $[Ar]4s^{2}3d^{10}4p^{5}$ means total electrons \(18+2 + 10+5=35\).
• The full electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}\).

Answer:

Element	Spectroscopic (Full)	Shorthand	Last Subshell	Valence Rule Used
Fe	\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}\)	\([Ar]4s^{2}3d^{6}\)	\(3d + 4s\)	Transition
Cu	\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{10}\)	\([Ar]4s^{1}3d^{10}\)	\(3d\)	Transition
Br	\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}\)	\([Ar]4s^{2}3d^{10}4p^{5}\)	\(4p\)	Main - group