Question

determine what elements are denoted by the following electron configurations: 21) 1s²2s²2p⁶3s²3p⁴ 22) 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s¹ 23) kr 5s²4d¹⁰5p³ 24) xe 6s²4f¹⁴5d⁶ 25) rn 7s²5f¹¹ determine which of the following electron configurations are not valid: 26) 1s²2s²2p⁶3s²3p⁶4s²4d¹⁰4p⁵ 27) 1s²2s²2p⁶3s³3d⁵ 28) ra 7s²5f⁸ 29) kr 5s²4d¹⁰5p⁵ 30) xe

Explanation:

Step1: Recall electron - configuration rules

The atomic number (Z) of an element is equal to the total number of electrons in a neutral atom. For noble - gas core notations, we add the number of electrons in the noble - gas core to the remaining electrons.

Step2: Calculate atomic number for 21

For $1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$, sum the electrons: $2 + 2+6 + 2+4=16$. The element with atomic number 16 is sulfur (S).

Step3: Calculate atomic number for 22

For $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{1}$, sum the electrons: $2 + 2+6 + 2+6 + 2+10 + 6+1 = 37$. The element with atomic number 37 is rubidium (Rb).

Step4: Calculate atomic number for 23

The noble - gas Kr has 36 electrons. For $[Kr]5s^{2}4d^{10}5p^{3}$, add the remaining electrons: $36+2 + 10+3 = 51$. The element with atomic number 51 is antimony (Sb).

Step5: Calculate atomic number for 24

The noble - gas Xe has 54 electrons. For $[Xe]6s^{2}4f^{14}5d^{6}$, add the remaining electrons: $54+2 + 14+6 = 76$. The element with atomic number 76 is osmium (Os).

Step6: Calculate atomic number for 25

The noble - gas Rn has 86 electrons. For $[Rn]7s^{2}5f^{11}$, add the remaining electrons: $86+2 + 11 = 99$. The element with atomic number 99 is einsteinium (Es).

Step7: Check validity for 26

The order of filling orbitals is incorrect. After $4s^{2}$, the next orbitals to fill are $3d$ and then $4p$. So $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}4d^{10}4p^{5}$ is not valid.

Step8: Check validity for 27

The $3s$ orbital can hold a maximum of 2 electrons. So $1s^{2}2s^{2}2p^{6}3s^{3}3d^{5}$ is not valid.

Step9: Check validity for 28

Ra is not a noble - gas. Noble - gas core notation should use a noble - gas. So $[Ra]7s^{2}5f^{8}$ is not valid.

Step10: Check validity for 29

$[Kr]5s^{2}4d^{10}5p^{5}$ is a valid electron configuration for iodine (I).

Step11: Check validity for 30

$[Xe]$ is not a complete electron configuration for an element. It just represents the xenon noble - gas core.

Answer:

1. S
2. Rb
3. Sb
4. Os
5. Es
6. Not valid
7. Not valid
8. Not valid
9. Valid
10. Not valid