Chemistry
(a) State the rule according to which electrons are filled in various energy levels.
(b) Give the number of electrons that can be present in the first four shells of an atom using this rule.
(c) What is the maximum number of electrons present in the outermost (valence) shell ?
Atomic Structure
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Answer
(a) Neil Bohr and Charles Bury proposed a scheme for distribution of electrons in different shells of an atom based on the formula 2n2, where n denotes the number of shell.
(b) The maximum number of electrons in each shell or orbit is determined by the formula 2n2, where n is the number of shell.
K shell, n=1, no. of electrons = 2 x 12 = 2
L shell, n=2, no. of electrons = 2 x 22 = 8
M shell, n=3, no. of electrons = 2 x 32 = 18
N shell, n=4, no. of electrons = 2 x 42 = 32
(c) The atom's outermost shell needs 2 electrons for stability (duplet rule) if it has only one shell. If it has multiple shells, it requires 8 electrons (octet rule) in the outermost shell for stability.
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