Question

Match the following elements with the correct electron configuration.


1s22s22p63s23p6


1s22s22p63s23p64s23d5


[Ar] 4s2


1s22s22p62d103s23p3


[Kr] 5s24d10

1.
Cd

2.
P

3.
Ca

4.
Ar

5.
Mn

Answer 1

To do this all you will have to do is just work out the electron configuration of each of the elements you are given.
To do this, as none of them are ions you can just look at the atomic number of each element on the periodic table and you will see how many electrons are in the element (atomic number = proton number and electron number in neutral atoms)
You will also need to know how many electrons and orbitals each sub-shell can hold. (baring in mind orbitals can only hold a max of 2 electrons travelling in opposite directions)
s sub shell = 1 orbital that can hold a max of 2 electrons
p sub shell = 3 orbitals that can hold a max of 6 electrons
d sub shell = 5 orbitals that can hold a max of 10 electrons

Now lets write the electron configuration of each element provided.

Cd has 48 electrons.
This means: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
This means that the correct configuration for this element is: [Kr] 5s2 4d10 (the [Kr] means the configuration of krypton ADD the shells in front of the symbol, in this case krypton + 5s2 and 4d10)

From this im sure you can work the rest out. I hope this helps