Assertion (A): Cobalt was placed before nickel in the Mendeleev periodic table.
Reason (B): Cobalt has less atomic mass than nickel.

see full answer

Start JEE / NEET / Foundation preparation at rupees 99/day !!

21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!

An Intiative by Sri Chaitanya

Both A and R are true and R is the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are true but R is not the correct explanation of A.

answer is C.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

This was done to ensure that the elements with similar chemical properties were put in the same group. Due to this, cobalt was placed before nickel in spite of the fact that cobalt has a higher atomic mass than a nickel.

Watch 3-min video & get full concept clarity

tricks from toppers of Infinity Learn

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Books for IIT JEE

Best Books for NEET

🔥 Start Your JEE/NEET Prep at Just ₹1999 / month - Limited Offer! Check Now!

Get Expert Academic Guidance – Connect with a Counselor Today!