Verified answer

Explanation:

Atomic radius: The distance between the nucleus and the valence shell of an atom is called the atomic radius.

The atomic radius of an atom is expressed in the units of Picometer (pm)

[tex] \bf \: 1pm \: = 10^{ - 12} m[/tex]

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The elements Cl, I, and Br belong to 17th group of the periodic table.

In a group of the periodic table, as we move from top to down,

• The number of shell increases at each step
• The nuclear charge on the nucleus of an atom increases.

Both of these factors have opposing effects on the size of the atom. Due to addition of a new shell at each step, the size of the atom tends to increase, but due to increase in nuclear charge on the nucleus, the outermost electrons are pulled strongly by the nucleus which tends to decrease the size of the atom.

But the effect of the addition of a new shell at each step overcomes the effect of an increase in nuclear charge and overall, as we move from top to down in a group, the atomic size increases.



Thus, the order of atomic radius among Cl, I, and Br is Cl < I < Br and the atomic radius of Cl , l and Br are 99, 133, 114 pm respectively.

Explanation:

the valence electrons experience less attractive force from the nucleus and are held less tightly resulting in the increased atomic radius. Thus, their atomic radii increase in the following order down the group. Hence, the atomic radii of Cl, I, and Br are 99, 133, and 114 pm, respectively.