Question

match the letter of the following electron configurations with the number of valence electrons. note: valence electrons for transition metals are omitted due to the presence of additional d subshell electrons. electron configurations a. 1s² 2s² 2p⁶ 3s² 3p⁵ b. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰5p³ c. 1s² 2s² 2p⁶ 3s² 3p⁴ d. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² e. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ electron configurations a. b. c. d. e. number of valence electrons: choose choose choose choose choose

Explanation:

Step1: Recall valence - electron rule

Valence electrons are in the outermost shell. For the given electron - configurations, we consider the electrons in the highest - numbered shell.

Step2: Analyze configuration A ($1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$)

The highest - numbered shell is 3. The number of electrons in shell 3 is $2 + 5=7$.

Step3: Analyze configuration B ($1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{3}$)

The highest - numbered shell is 5. The number of electrons in shell 5 is $2+3 = 5$.

Step4: Analyze configuration C ($1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$)

The highest - numbered shell is 3. The number of electrons in shell 3 is $2 + 4=6$.

Step5: Analyze configuration D ($1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}$)

The highest - numbered shell is 5. The number of electrons in shell 5 is 2.

Step6: Analyze configuration E ($1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}$)

The highest - numbered shell is 4. The number of electrons in shell 4 is $2+6 = 8$.

Answer:

A. 7
B. 5
C. 6
D. 2
E. 8