What do you understand by the term "electronic configuration" of an element? Write down the electronic configuration of oxygen (At. No. = 8).
An element has an atomic number 12. How many electrons will be present in the K, L and M energy shells of its atom?

Distribution of electrons around the nucleus in certain shell/orbits is known as the electronic configuration of an element.
Electronic configuration of oxygen = 2, 6

Electronic configuration of the element with atomic number 12 will be 2, 8, 2.
Electrons present is K subshell will be 2.
Electrons present is L subshell will be 8.
Electrons present is M subshell will be 2.