Why are atomic radii of noble gases larger than those of halogens?

1.	Why are atomic radii of noble gases larger than those of halogens?
Answer» Halogens (F to At) are in group 17 while noble gas (He to Rn) are in group 18. Generally, atomic radii decrease on moving from left to right in a period, hence atomic radii of noble gases are expected to be smaller than those of halogens. Due to the crowding of eight electrons in the valence shell, electron density increases and there is an appreciable electronic repulsion between them. To decrease this repulsion and electronic density, the volume of valence shell increases. Therefore atomic radii of noble gases are larger than those of halogens.

Answer»

Halogens (F to At) are in group 17 while noble gas (He to Rn) are in group 18.
Generally, atomic radii decrease on moving from left to right in a period, hence atomic radii of noble gases are expected to be smaller than those of halogens.
Due to the crowding of eight electrons in the valence shell, electron density increases and there is an appreciable electronic repulsion between them.
To decrease this repulsion and electronic density, the volume of valence shell increases.

Therefore atomic radii of noble gases are larger than those of halogens.

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