Question

electronic configuration practice- use periodic table with electron configuration table
in the space below, write the unabbreviated electron configurations of the following elements:

1. sodium
2. magnesium
3. iron
4. potassium
5. selenium

in the space below, write the abbreviated electron configurations of the following elements:

1. cobalt
2. silver
3. tellurium
4. radium

10.iodine
determine what elements are denoted by the following electron configurations:
11.1s² 2s² 2p⁶ 3s² 3p⁴
12.1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰4p⁶ 5s¹
13.kr 5s² 4d¹⁰5p³
explain what is wrong with the following electron configurations:
14.1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4d¹⁰4p⁶
15.1s² 2s² 2p⁶ 3s³ 3d⁵
identify the element and determine the valence electrons.

electron configuration	element symbol	valence electrons
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰4p⁶ 5s¹
1s²2s²2p⁶3s²3p⁶4s²3d⁶
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁵
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁵
1s² 2s² 2p⁶ 3s² 3p⁵

Explanation:

Step1: Recall electron - filling rules

Electrons fill orbitals in order of increasing energy (Aufbau principle), with s - orbitals holding a maximum of 2 electrons, p - orbitals holding 6, d - orbitals holding 10, and f - orbitals holding 14.

Step2: Unabbreviated electron configurations

Sodium (Na, atomic number = 11)

$1s^{2}2s^{2}2p^{6}3s^{1}$

Magnesium (Mg, atomic number = 12)

$1s^{2}2s^{2}2p^{6}3s^{2}$

Iron (Fe, atomic number = 26)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}$

Potassium (K, atomic number = 19)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}$

Selenium (Se, atomic number = 34)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{4}$

Step3: Abbreviated electron configurations

Cobalt (Co, atomic number = 27)

$[Ar]4s^{2}3d^{7}$

Silver (Ag, atomic number = 47)

$[Kr]4d^{10}5s^{1}$

Tellurium (Te, atomic number = 52)

$[Kr]5s^{2}4d^{10}5p^{4}$

Radium (Ra, atomic number = 88)

$[Rn]7s^{2}$

Iodine (I, atomic number = 53)

$[Kr]5s^{2}4d^{10}5p^{5}$

Step4: Identify elements from electron configurations

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$

Sulfur (S) since the total number of electrons is 16.

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{1}$

Rubidium (Rb) as the total number of electrons is 37.

$[Kr]5s^{2}4d^{10}5p^{3}$

Antimony (Sb) as adding the electrons from $[Kr]$ (36) and the additional 15 electrons gives 51 electrons.

Step5: Find errors in electron configurations

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}4d^{10}4p^{6}$

The 4d - subshell should not fill before the 5s - subshell. The correct order is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}$

$1s^{2}2s^{2}2p^{6}3s^{3}3d^{5}$

The 3s - orbital can only hold 2 electrons, so it should be $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}$ (following Hund's rule and Aufbau principle).

Step6: Identify elements and valence electrons

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{1}$

Element: Rubidium (Rb), Valence electrons: 1

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}$

Element: Iron (Fe), Valence electrons: 8 (2 in 4s and 6 in 3d)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}$

Element: Bromine (Br), Valence electrons: 7

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}$

Element: Bromine (Br), Valence electrons: 7

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$

Element: Chlorine (Cl), Valence electrons: 7

Answer:

1. $1s^{2}2s^{2}2p^{6}3s^{1}$
2. $1s^{2}2s^{2}2p^{6}3s^{2}$
3. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}$
4. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}$
5. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{4}$
6. $[Ar]4s^{2}3d^{7}$
7. $[Kr]4d^{10}5s^{1}$
8. $[Kr]5s^{2}4d^{10}5p^{4}$
9. $[Rn]7s^{2}$
10. $[Kr]5s^{2}4d^{10}5p^{5}$
11. Sulfur (S)
12. Rubidium (Rb)
13. Antimony (Sb)
14. 4d - subshell filled before 5s - subshell; correct is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}$
15. 3s - orbital has 3 electrons instead of 2; correct is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}$
16. Rubidium (Rb), 1
17. Iron (Fe), 8
18. Bromine (Br), 7
19. Bromine (Br), 7
20. Chlorine (Cl), 7