Question

question 31
1 pts
which of the following atoms have the same electron configuration as ar: (pick all that apply.
ar 1s² 2s² 2p⁶ 3s² 3p⁶
□ na⁺
□ cl⁻
□ kr
□ p³⁻
□ br⁻
□ s²⁻
□ mg²⁺
□ k⁺
□ ca²⁺

Explanation:

Step1: Determine electron - count of Ar

Argon (Ar) has an electron configuration of $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}$, and it has 18 electrons.

Step2: Analyze each ion/atom

• $Na^{+}$: Sodium (Na) has 11 electrons. $Na^{+}$ has 10 electrons ($11 - 1$), so it does not have the same electron - configuration as Ar.
• $Cl^{-}$: Chlorine (Cl) has 17 electrons. $Cl^{-}$ has 18 electrons ($17+1$), so it has the same electron - configuration as Ar.
• $Kr$: Krypton (Kr) has 36 electrons, so it does not have the same electron - configuration as Ar.
• $P^{3 - }$: Phosphorus (P) has 15 electrons. $P^{3 - }$ has 18 electrons ($15 + 3$), so it has the same electron - configuration as Ar.
• $Br^{-}$: Bromine (Br) has 35 electrons. $Br^{-}$ has 36 electrons ($35 + 1$), so it does not have the same electron - configuration as Ar.
• $S^{2 - }$: Sulfur (S) has 16 electrons. $S^{2 - }$ has 18 electrons ($16+2$), so it has the same electron - configuration as Ar.
• $Mg^{2 + }$: Magnesium (Mg) has 12 electrons. $Mg^{2 + }$ has 10 electrons ($12 - 2$), so it does not have the same electron - configuration as Ar.
• $K^{+}$: Potassium (K) has 19 electrons. $K^{+}$ has 18 electrons ($19 - 1$), so it has the same electron - configuration as Ar.
• $Ca^{2 + }$: Calcium (Ca) has 20 electrons. $Ca^{2 + }$ has 18 electrons ($20 - 2$), so it has the same electron - configuration as Ar.

Answer:

$Cl^{-}$, $P^{3 - }$, $S^{2 - }$, $K^{+}$, $Ca^{2 + }$