JEE MAIN - Chemistry (2011 - No. 9)
The outer electron configuration of $$Gd$$ (Atomic No. $$64$$) is :
$$4{f^3}\,5{d^5}\,6{s^2}$$
$$4{f^8}\,5{d^0}\,6{s^2}$$
$$4{f^4}\,5{d^4}\,6{s^2}$$
$$4{f^7}\,5{d^1}\,6{s^2}$$
Paliwanag
The configuration of $$Gd$$ is $$4{f^7}\,5{d^1}\,6{s^2}.$$