Question

electron configuration practice worksheet
in the space below, write the unabbreviated electron configurations of the following elements:

1. sodium
2. iron
3. bromine
4. barium
5. neptunium

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

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

determine what elements are denoted by the following electron configurations:

1. 1s²2s²2p⁶3s²3p⁴
2. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s¹
3. kr 5s²4d¹⁰5p³
4. xe 6s²4f¹⁴5d⁶
5. rn 7s²5f¹¹

determine which of the following electron configurations are not valid:

1. 1s²2s²2p⁶3s²3p⁶4s²4d¹⁰4p⁵
2. 1s²2s²2p⁶3s²3d²
3. ra 7s²5f⁸
4. kr 5s²4d¹⁰5p⁶
5. xe

Explanation:

Step1: Recall electron - filling rules

Use the Aufbau principle, Pauli - exclusion principle, and Hund's rule to write electron configurations.

Step2: Write unabbreviated electron configurations

• Sodium (Na, atomic number = 11): $1s^{2}2s^{2}2p^{6}3s^{1}$
• Iron (Fe, atomic number = 26): $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}$
• Bromine (Br, atomic number = 35): $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}$
• Barium (Ba, atomic number = 56): $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}$
• Neptunium (Np, atomic number = 93): $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}4f^{14}5d^{10}6p^{6}7s^{2}5f^{4}6d^{1}$

Step3: Write 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): $[Kr]4d^{10}5s^{2}5p^{4}$
• Radium (Ra, atomic number = 88): $[Rn]7s^{2}$
• Lawrencium (Lr, atomic number = 103): $[Rn]7s^{2}5f^{14}6d^{1}$

Step4: Identify elements from electron configurations

• $1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$: Sulfur (S)
• $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{1}$: Rubidium (Rb)
• $[Kr]5s^{2}4d^{10}5p^{3}$: Antimony (Sb)
• $[Xe]6s^{2}4f^{14}5d^{6}$: Osmium (Os)
• $[Rn]7s^{2}5f^{11}$: Mendelevium (Md)

Step5: Determine invalid electron configurations

• $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}4d^{10}4p^{5}$: Invalid, should be $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}$
• $1s^{2}2s^{2}2p^{6}3s^{2}3d^{2}$: Invalid, 3p sub - shell should be filled before 3d ($1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{2}$ is correct for titanium)
• $[Ra]7s^{2}5f^{8}$: Invalid, Ra is not a noble gas, should use Rn as the noble - gas core
• $[Kr]5s^{1}4d^{10}5p^{6}$: Invalid, 5s should be filled before 5p ($[Kr]4d^{10}5s^{2}5p^{6}$ is correct for xenon)
• $[Xe]$: Invalid, this is just a noble - gas symbol, not a complete electron configuration for an element other than xenon

Answer:

1. Sodium: $1s^{2}2s^{2}2p^{6}3s^{1}$
2. Iron: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{6}$
3. Bromine: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}$
4. Barium: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}$
5. Neptunium: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}4f^{14}5d^{10}6p^{6}7s^{2}5f^{4}6d^{1}$
6. Cobalt: $[Ar]4s^{2}3d^{7}$
7. Silver: $[Kr]4d^{10}5s^{1}$
8. Tellurium: $[Kr]4d^{10}5s^{2}5p^{4}$
9. Radium: $[Rn]7s^{2}$
10. Lawrencium: $[Rn]7s^{2}5f^{14}6d^{1}$
11. Sulfur (S)
12. Rubidium (Rb)
13. Antimony (Sb)
14. Osmium (Os)
15. Mendelevium (Md)
16. Invalid
17. Invalid
18. Invalid
19. Invalid
20. Invalid