Question

Use Lewis symbols to show electron transfer between the following atoms to form cations and anions:

1. K and S 
2. Ca and O 
3. Al and N.

Answer 1

Lewis symbols and electron transfer:

Lewis symbols represent the valence electrons of atoms using dots around the atomic symbol. Electron transfer from a metal to a non-metal results in the formation of cations and anions.

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(a) Potassium (K) and Sulphur (S)

Potassium has 1 valence electron and sulphur has 6 valence electrons. Two potassium atoms each donate one electron to sulphur.

K· + ··S·· + ·K → K⁺ + K⁺ + [··S··]²⁻

Thus, K⁺ and S²⁻ ions are formed.

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(b) Calcium (Ca) and Oxygen (O)

Calcium has 2 valence electrons and oxygen has 6 valence electrons. Calcium transfers both electrons to oxygen.

Ca·· + ··O·· → Ca²⁺ + [··O··]²⁻

Thus, Ca²⁺ and O²⁻ ions are formed.

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(c) Aluminium (Al) and Nitrogen (N)

Aluminium has 3 valence electrons and nitrogen has 5 valence electrons. Three electrons are transferred from aluminium to nitrogen.

Al··· + ··N··· → Al³⁺ + [··N··]³⁻

Thus, Al³⁺ and N³⁻ ions are formed.

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Conclusion:

Lewis symbols clearly show the transfer of valence electrons from metals to non-metals, leading to the formation of stable cations and anions.