An atom with the electronic configuration, 1S2 2S2 2P6 3S2 3p6 4s2 3d6 is that of a/an

 An atom with the electronic configuration, 1S2 2S2 2P6 3S2 3p6 4s2 3d6 is that of a/an

A. alkali metal.

B. alkaline-earth metal.

C. halogen.

D. noble gas.

E. transition metal.

The Correct answer is E. transition metal.

Explanation: There are many ways of answering this questions

First way of sourcing answer: by adding all the valence electron of the subsidiary or azimuthal quantum number together.

1S2 2S2 2P6 3S2 3p6 4s2 3d6

    2+   2+   6+   2+   6+  2+   6 = 26

From the result you will observe that the element is iron with the atomic number of 26. Also element with the atomic number from 21 to 30 are called transition metals. This element are

scandium 21

titanium 22

vanadium 23

chromium 24

manganese 25

iron 26

cobalt 27

nickel 28

copper 29

zinc 30

So you see that iron is one of them

Second way of sourcing answer: Take a look at the last sub orbital 

1S2 2S2 2P6 3S2 3p6 4s2 3d6

That is 3d6. This 3 represent third period which correspond to the third period of the periodic table where the transition metals begin after calcium. Hence the two ways point to transition metals.

QUESTION SOURCE: NECO OBJECTIVE QUESTION 2001 QUESTION 37