Question

Easy trick to find group no of element​

Answer 1

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In Inorganic chemistry, first thing is to learn periodic table thoroughly. Know the periodic table & you will enjoy the inorganic chemsitry learning.

To locate the block, period & group of an element, go through following steps:

Remember group 1 elements & group 18 elements with atomic number.

How to do that ?

Group 1 Trick :

HLiNa (pronounced as “Helina”) ki Rab Cs(pronounce as “Se”) Fariyad.

(Translation - Helina complaints to god)

For calculating atomic no. Remember these magic nos. 2, 8,8, 18, 18, 32.

Add these magic nos to atomic no for getting the atomic no of next one.

At no-Element

1-Hydrogen, (Remember atomic no. Of H,then add 1st magic no 2 & atomic no of next one i.e 1 + 2 = 3

3-Lithium,(3 + 8 = 11)

11-Na (Sodium) (11 + 8 = 19)

19-Rubidium,(19 + 18 = 37)

37-Cesium,(37 + 18 = 55)

37-Francium

Group 18 Trick :

HeNeArKr ne Xe Runs Banaye

(Translation - Henearkar made X runs)

At no - Element

2-Helium, (2 itself is a magic no. So add 8 to get next atomic no)(2 + 8 = 10)

10-Neon,(10 + 8 = 18)

18-Argon,(18 + 18 = 36)

36-Krypton,(36 + 18 = 54)

54-Xenon,(54 + 32 = 86)

86-Radon

Now just remember 2 mnemonics, atomic no.of H & He is already easy to remember, so just add magic nos to get atomic no of next element by saying mnemonic.

Calculate this fast on fingers.

Now coming to question, lets take an example.

Locate the element with atomic number 40.

Follow these steps & do it on your fingers. Atomic no 40, Count on your fingers from first atomic no of first group by adding magic nos like this & reach to the range of 40 as asked,like this

1. 13 (1 + 2 = 3)
2. 11 (3 + 8 = 11 )
3. 19 (11 + 8 = 19)
4. 37 (19 + 18 = 37)
5. 55 (37 + 18 = 55)

Stop here,as we have reached more than 40, this means element lies between 37 and 54 (54, ending point i got because next step starts with 55)

Now as step is 5th (5th cut on finger), in which we got range of 40 (i.e 37 to 54), PERIOD IS 5 & for group start counting on finger grp nos from 37 (starting point of this range) to reach till our 40th number & here we stop on 4th cut on finger and arrives on 40 so GROUP IS 4

If number asked is nearby to group nos of group 18 then do counting of group in reverse order.e.g 33. This falls in the range of 36 number. If we count like 2,10,18,36 (grp 18 atomic nos) on finger,

Stop here 34 is less than 36. Its on 4th cut on finger. So PERIOD IS 4, now from 36 - count group no in reverse to reach till 33.i.e 18,17,16,15 .so GROUP IS 15.Learn the skeleton of periodic i.e shape. So that you can learn blocks. As there is hydride gap in 1st period so bit change there.

s block - group 1 and 2

d block - group 3 to 12

p block - group 13 to 17

f block - group 3 (57 -71, 89–103)

In last two periods you have to keep in mind about f-block.

Learn mnemonics for all elements then you will be able to name an element too.

Once you repeat these steps, you can calculate this way faster. Tested timing is 20 seconds.

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Answer 2

You can find group number by seeing the valency if the valency is less than 2 the group will be 1 or 2. but if the valency is greater than 2 than you have to add 10. and you will get group number

For example :- Valency of chlorine is 7 so it's group will be 10+7=17