Question

1. choose the best answer.

what is the electron configuration for aluminum?
1s²2s²2p⁶3s²
1s²2s²2p⁶3s²3p¹
1s²2s²2p⁵
1s²2s²2p⁶3s²3p⁶4s

1. choose the best answer.

what period is calcium in?
20
40
2
4

Explanation:

Step1: Determine the atomic number of aluminum

Aluminum (Al) has an atomic number of 13. This means it has 13 electrons.

Step2: Fill the electron orbitals

• The 1s orbital can hold 2 electrons: \(1s^{2}\)
• The 2s orbital can hold 2 electrons: \(2s^{2}\)
• The 2p orbital can hold 6 electrons: \(2p^{6}\)
• The 3s orbital can hold 2 electrons: \(3s^{2}\)
• After filling 1s²2s²2p⁶3s², we have used \(2 + 2+6 + 2=12\) electrons. The remaining 1 electron goes into the 3p orbital: \(3p^{1}\)

So the electron configuration of aluminum is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{1}\)

Step3: Determine the period of calcium

Calcium (Ca) has an atomic number of 20. In the periodic table, the period number is equal to the highest - energy level (principal quantum number \(n\)) of the valence electrons.

• The electron configuration of calcium is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}\). The highest - energy level is \(n = 4\)

Answer:

1. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{1}\)
2. 4