(i) Element X has two valence electrons in the M - shell.
(ii) In element Y, the electrons are distributed in the first three shells. It has eight
electrons in the M-shell.
(iii) Element Z has eight electrons in the penultimate shell, i.e., M.
Based on the information given in the above three statements, answer the following
questions.
(a) Give the electronic configuration of X.
(b) Which element is stable among X, Y and Z and why?
(c) In which atom of an element is the number of electrons distributed in the four shells?
(d) What is the atomic number of Z in which the number of electrons in the first and the
last shell are not the same?
(e) What are the number of electrons and protons present in Y?
Answers
Explanation:
In chemistry and atomic physics, an electron shell, or a principal energy level[clarification needed], may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on farther and farther from the nucleus. The shells correspond to the principal quantum numbers (n = 1, 2, 3, 4 ...) or are labeled alphabetically with the letters used in X-ray notation (K, L, M, …).
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.[1] Since electrons are electrically attracted to the nucleus, an atom's electrons will generally occupy outer shells only if the more inner shells have already been completely filled by other electrons. However, this is not a strict requirement: atoms may have two or even three incomplete outer shells. (See Madelung rule for more details.) For an explanation of why electrons exist in these shells see electron configuration.[2]
The electrons in the outermost occupied shell (or shells) determine the chemical properties of the atom; it is called the valence shell.
Each shell consists of one or more subshells, and each subshell consists of one or more atomic orbitals.