Question

Without consulting the periodic table, select from each of the following sets, the elements belonging to the same group of the periodic table

• A. Z=11, 3, 20, 37
• B. Z=12, 38, 4, 88
• C. Z=31, 13, 81, 50
• D. Z=21, 39, 90, 57

Answer 1

The correct option is B

Z=12, 38, 4, 88

12 (Mg), 4 (Be), 38 (Si), 88 (Ra) belong to group 2 of the periodic table.

The way to go about this problem is to add the magic numbers starting with the smallest number in the series.

Magic numbers are 2, 8, 8, 18, 18, 32 and so on. But keep in mind to note the period you are adding to.

If we take options (a) for example, 3 is in the second period. So, 3 + 8 = 11, 11 + 8 = 19, 19 + 18 = 37, 37 + 18 = 55, 55 + 32 = 87.
So, atomic numbers 3, 11, 19, 37, 55 and 87 would be in the same group. Option (a) is wrong. You can check for other options too.

Now, 4 + 8 = 12, 12 + 8 = 20, 20 + 18 = 38, 38 + 18 = 56, 56 + 32 = 88
This is option (b).