Question

The van der Waals radii \[O,N,Cl,F\;\] and increase in the order:
A.\[F,O.N,Ne,Cl\]
B.\[Ne,F,O,N,Cl\]
C.\[F,Cl,O,N,Ne\]
D.\[N,O,F,Ne,Cl\]

Answer 1

Hint: To answer this question, you should recall the trends in the periodic table. The modern periodic law developed by Moseley states that the physical and chemical properties of elements are the periodic function of their atomic number. The radii of atoms depends upon the net effective nuclear charge.

Complete step by step answer:
The systematic arrangement of elements according to Moseley’s law discloses certain periodic trends in the properties of elements. As it we know that \[{\text{radius }}\alpha \dfrac{{\text{1}}}{{{{\text{Z}}_{{\text{eff}}}}}}\], where \[{{\text{Z}}_{{\text{eff}}}}\] is the effective charge over an atom.
When we move along a period towards right from left the \[{{\text{Z}}_{{\text{eff}}}}\] increase leading to a decrease in the radius.
Although, in a period noble gases have the largest van der Waals radius compared to all the elements in the same period. The reason for this is the weaker the intermolecular force of attraction, the more electron-electron repulsion.
When we move down a group, the \[{{\text{Z}}_{{\text{eff}}}}\] decreases leading to an increase in radius down the group. Another important thing to remember is that when moving along a period, the atomic radius is supposed to decrease but oxygen has slightly higher atomic radius than nitrogen. The reason for this observation is that because nitrogen has an electronic configuration \[2{p^3}\] of the outermost shell having its orbital half- filled. This results in less repulsion and more exchange energy between the electrons.
However, in oxygen we have \[2{p^4}\] as the electronic configuration of the outermost shell. This results in one paired electron in one of its orbitals. This leads to interelectronic repulsion and thus increases the atomic radius slightly. So, the order of radii is-
\[F < Cl < O < N < Ne\].

Hence, the correct option is C.

Note:
Let us summarize the trends of fundamental properties of an element: Atomic Radii and Ionic radii: The atomic radii and ionic radii of elements decrease while moving from left to right in a period. Ionization Enthalpy: Across a period in the periodic table, ionization energy generally increases. However, when we see the trend of ionization enthalpy in the groups, it decreases from top to bottom in a group. Electron gain enthalpy: Electron gain enthalpy becomes more negative as we move from left to right in a period. Electron gain enthalpy is negative when energy is released while accepting an electron. While it is positive when energy is supplied to an atom while adding an electron.