EVERYDAY SCIENCE

Detailed explanation-1: -Valence electrons are the electrons in the outermost shell, or energy level, of an atom. For example, oxygen has six valence electrons, two in the 2s subshell and four in the 2p subshell.

Detailed explanation-2: -This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.

Detailed explanation-3: -Valency tells us only the total number of electrons present in the outermost shell of the atom and so it is different from the atomic number. Therefore, the outermost shell of an atom is known as valence shell.

Detailed explanation-4: -Why is the third period contains 8 elements and not 18? The third period contains 8 elements because it corresponds to the filling of the 3s and 3p subshells (of the third shell) which take a total of 8 electrons, two in the 3s and 6 in the 3p subshell.

Detailed explanation-5: -For transition elements, the last electron (differentiating electron) enters the d orbital of the penultimate shell i.e. (n−1) d orbital where n is the outermost shell.