Atomic Structure: 1.14 deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table

Electronic configuration 

The arrangement of electrons into shells for an atom is known as its electronic configuration

As you are given a periodic table in the exam, you don't have to remember all of them, just be able to state them when asked.

They are given in shorthand notations, e.g.
Carbon has 6 electrons, so its EC would be 2.4
Magnesium has 12 electrons, so its EC would be 2.8.2