Atomic Radius :
One of the important Periodic Table trend is Size of the Atom / Atomic Radius is Explained in this blog
Introduction – The Periodic Table :-
Periodic Table of Elements :-
The periodic table, also known as Periodic table of elements. It is the address book of elements. The Elements are arranged here in the increasing order of atomic number. It keeps the all information about size, nature, property, behavior towards other elements, strength, weakness. However these information’s are hidden in the periodic table so we have to learn and explore those Information.
I will Explain these topic One by one,
The Secret of these information’s are lies in the subatomic particles of atom and the effects shown by those particles like Proton, neutrons, electrons.
Size of the atom :- (Across the Group)
Let’s Examine the First Column (Group) of the Periodic Table. As you go down the Column (Group), you can see there is an increase in Orbit. So therefore the size of the atom is increase in going down the Group.
So therefore element in down of the group has Larger Size than Element present in Upper
Size of an Atom :- (Across the Period)
As you move through the Period (Row) Right to left, You can see that the number of orbit remains same but the number of electrons and number of protons are increased. This results in the Formation of Stronger Nuclear Force ( Attraction between Proton and Electron ) , It is capable of large binding of electons more closely. This results in Decrease of the size of atom.
So the element placed in the Right side of the Period (Row) is smaller when compared with element placed in Left of the same Period (Row)
When you observe the trends of atomic size across the period (Row),You will find that it is not steady as we expected. It decreases across the period (row) but when we move from the “d – block” to “p – block” there is a large contraction in size. And again after “f – block” you will see large contraction in size of “d – block “elements
What do you think about the Reason behind this unsteady trend in size ?
So first note down the factors responsible for the contractions in the size
• Nuclear Charge/Number of Protons Which pulls electrons towards nucleus like a tiny 🧲 Magnet
• Distance between the Outer electron and Nucleus, which prevents them to be pulled towards the nucleus.
Shielding Effect :-
Electrons in the inner shell can cancel some of the nuclear charge, so that the electron in the outer shell can experience the less attraction of Nucleus. This is called Shielding Effect. The Extent of Shielding caused by Sub- shells are different because every sub-shell has different structure.
Node :- Every Sub-shell has a place where no electron is present it is called as Node.
Presence of Node weakens the shielding effect of sub-shell. The number of Node can guessed by Azimuthal quantum number (l) .
• S subshell is spherical shaped and has l = 0 means has no nodes. So it has stronger Shielding tendency.
• P subshell is Dumbbell shaped and has l = 1 means has one node.
• D subshell is double dumbbell shaped and has l = 2 means it has two nodes.
• F subshell is complex shaped and has l = 3 means it has three nodes.
The order of shielding effect of different sub- shell are follows
This is the main reason of the size difference between (i) d block to p block and (ii) f block to d block.
(i) d block has two nodes and dumbbell shaped subshell, so it is a poorer shielding tendency when compared to p block. This the reason behind why Contraction of size between d block to p block
(ii) f block has three nodes and it is complex shaped subshell, so it is a poorer shielder when compared to d block.
Check Other Periodic Trends ( Properties) also
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