Answer:
These are experimentally reported values , The values are
A = Bromine = 1.12 Angstrom
B = Magnesium = 1.6
C = Sodium = 1.9
Order of Atomic radius :
<u>Sodium > Magnesium >Phosphorus > Bromine > Chlorine</u>
Explanation:
In order to explain the answer , look some basic concepts of the periodic table:
The periodic table is the arrangement of element in increasing order of their atomic number.
Modern periodic table is divided into two parts :
1. Periods : The horizontal rows are called the periods. There are seven periods in the periodic table.The period of the element tells about the electron shell.
For example the element of period 2 = contain 2 shell( from Li to Neon)
Along the period the<u> atomic size decreases</u>. This is because the effective nuclear charge increases along the period
2. Groups : The vertical columns are called the groups . The group number of the element tell about the number of electron in outermost shell.
For example the element of group 3 = has 3 electrons in their outermost shell(Boron , Aluminium , Gallium , Indium , Thallium)
Down the group the<u> atomic size increases</u> because each the number of shells increases on going down.
For example example :
Boron = 2 shells
Al = 3 shell , In = 4 shells
<u>The given table is :</u>
Bromine = 1.12
Chlorine = 0.97
Magnesium = 1.6
Sodium = 1.9
Phosphorus = 1.28
Order of size :
<u>Sodium > Magnesium >Phosphorus > Bromine > Chlorine</u>
How to proceed :
<u>1. First , find out their atomic number</u>
Bromine = 35
Chlorine = 17
Magnesium = 12
Sodium = 11
Phosphorus = 15
2.Find the electronic configuration :
Bromine = [Ar] 3d10 <u>4s2 4p5 </u>
Chlorine = [Ne] <u>3s2 3p5</u>
Magnesium = [Ne] <u>3s2</u>
Sodium = [Ne] <u>3s1</u>
Phosphorus = [Ne] <u>3s2 3p3</u>
3. Check the elements which belong to <u>halogen family</u> : They have smallest atomic radii. Here,<u> Bromine and chlorine .</u>
<u>These have smallest size because of more effective nuclear charge.</u>
.(These elements are present on Right side of the periodic table)
But Bromine = 4 shell and chlorine =3 shell
So Cl = smallest radii
Hence,<u>radii Bromine > Chlorine</u>
<u>4 .</u>Check the elements which belong to<u> "Alkali</u> "<u>family</u> : They have largest atomic radii. Here sodium.(These elements are present on extreme left side of the periodic table)
So Size , of <u>sodium = maximum</u>
Then search the alkaline metal ion : These are large in size , also present on left side of periodic table
Hence
Magnesium is second large atom
So trend is :
<u>Sodium > Magnesium >Phosphorus > Bromine > Chlorine</u>