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BECE Science 2024 Paper

Question : 7

Total: 40

Solution:

Concept:

The number of electron shells in an atom is equal to the number of different energy levels occupied by its electrons.

Explanation:

Write the electron configuration of each element:

{}_{19}\mathrm{K} = 2, 8, 8, 1

→ 4 shells

{}_{13}\mathrm{Al} = 2, 8, 3

→ 3 shells

{}_{15}\mathrm{P} = 2, 8, 5

→ 3 shells

{}_{5}\mathrm{B} = 2, 3

→ 2 shells

Hence, only potassium has four electron shells.

Answer:

Option A:

{}_{19}\mathrm{K}

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