Question

Describe the theory associated with the radius of an atom as it 

1. gains an electron 
2. loses an electro

Answer 1

1. When an atom gains an electron

When a neutral atom gains one or more electrons, it forms an anion.

• The number of protons (nuclear charge) remains the same, but the number of electrons increases.
• Electron–electron repulsion in the valence shell increases, and effective nuclear attraction per electron decreases.
• As a result, the electron cloud expands and the ionic radius becomes larger than the atomic radius.

In simple terms: \[ \text{Anion radius} \;>\; \text{neutral atom radius} \]

2. When an atom loses an electron

When a neutral atom loses one or more electrons, it forms a cation.

• The number of protons remains the same, but the number of electrons decreases.
• There is less electron–electron repulsion and the remaining electrons experience a stronger effective nuclear attraction.
• Sometimes, one outer shell may be completely lost, causing a big decrease in size.
• Therefore, the electron cloud contracts and the ionic radius becomes smaller than the atomic radius.

In simple terms: \[ \text{Cation radius} \;<\; \text{neutral atom radius} \]

Key Idea (LaTeX Summary)

\[ \text{Gain of electrons} \;\Rightarrow\; \text{more repulsion, weaker effective attraction, larger radius} \] \[ \text{Loss of electrons} \;\Rightarrow\; \text{less repulsion, stronger effective attraction, smaller radius} \]