Question

The correct order of increasing radii of the elements Na, Si, Aland P is:
(a) Si, Al, P, Na
(b) Al, Si, P, Na
(c) P, Si, Al, Na
(d) Al, P, Si, Na

Answer 1

Hint: The atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the centre of the nucleus to the boundary of the surrounding shells of electrons. In general, atomic radius decreases across a period and increases down a group. ... Down a group, the number of energy levels (n) increases, so there is a greater distance between the nucleus and the outermost orbital. This results in a larger atomic radius.

Complete step by step solution:
We have been provided with the elements Na, Si, Aland P,
We are supposed to arrange them in increasing order of their atomic radii,
So, for that: The atomic radii are the distance between an atom's nucleus and outer electron shell.
It is known that on moving down the group, the ionic radii increase and on moving across the period from left to right, ionic radii decrease.

Here, the biggest element would be Na then Al followed by Si and P. P is the smallest element among these.

So, the arrangement would be: P< Si< Al< Na,

Therefore, option (c) is correct.

Note: Ionic radius is the radius of a monatomic ion in an ionic crystal structure. Although neither atoms nor ions have sharp boundaries, they are sometimes treated as if they were hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice.