Question

Arrange the size of $ Na,N{a^ + },Cl,C{l^ - } $ in increasing order.

Answer 1

Hint: Atomic radii is the distance between the centre of the nucleus and the outermost valence electron of the atom. To determine the size of any atom or ion, we’ll have to know its atomic or ionic radius. To solve this question, we’ll recall the trend of atomic size across the period and down the group.

Complete answer:
We have studies that the size of the atom decreases as we move from left to right across a period of the periodic table. This is because when we move across the period the atomic number goes on increases, which increases the no. of electrons in the atom. The effective nuclear charge also increases, and it attracts the electrons more effectively. This leads to the atoms being pulled more strongly by the nucleus and reducing the size of the atom.
Now, as we move down the group, the size increases. This is because the no. of orbitals in an atom increases and the electrons tend to move farther from the nucleus. Also, the shielding due to the electrons doesn’t allow the electrons to be attracted effectively, due to which the electrons are pushed far off and the atomic size increases.
We are given four species, $ Na,N{a^ + },Cl,C{l^ - } $ . Na belongs to the first group of the periodic table and Cl belongs to group XVII of the periodic table. Hence the size of $ Na > Cl $ as they belong to the same period.
The size of the cations formed are always smaller than the parent atom. Cations are formed when an electron is lost from the outermost shell. As one electron is lost the nuclear attraction increases and the size of the ion reduces. Hence the size of $ Na > N{a^ + } $
The size of anions are bigger than their parent atoms, as one electron is added to the outermost shell of the atom. Because of this the ionic radius increases and thus the size of $ Cl < C{l^ - } $ . The size of $ C{l^ - } > N{a^ + } $ .
The correct order of size of atomic radii is: $ Cl < N{a^ + } < C{l^ - } < Na $ .

Note:
Remember that the anions are always bigger than cations whatsoever. The size of the atoms, if we give a neutral, cation and anionic atom will be as: $ Anion > Neutral > Cation $ . If a covalent bond is present between two atoms, divide the bond length by two to know the atomic radius.