An element M has an atomic number 9 and atomic mass 19. Its ion will be represented by
M
M+2
M-
M-2
An element M has an atomic number 9 and atomic mass 19. Its ion will be represented by
M
M+2
M-
M-2
The correct option is C M-
Valency
The number of electrons gained or lost by the electron to achieve a stable electronic configuration is called its valency. Atoms form ions by the addition or removal of electrons. The ions formed by the removal of electrons are positive ions and are called cations. The ions formed by the addition of electrons are negatively charged and are called anions. The most stable ion formed by an atom is determined from its number of valence electrons.
A stable configuration is obtained when a shell is completely filled. The ions with the stable configuration will be the stable ion of the element. The maximum occupancy of each shell is in the order 2, 8, 8,18,18,….
The sign on the ion represents whether an electron is added or removed and the magnitude of charge represents the number of electrons added or removed from the atom.
Consider metal M. The number of electrons in the metal is 9. Therefore, its electronic configuration is 2,7.
Explanation for wrong answers
(A) The metal atom contains 7 electrons in the outermost shell. Therefore, the neutral form of the meal does not have complete octet. Therefore, option (A) is incorrect.
(B) M+2 ion is formed by the removal of 2 electrons. When two electrons are removed from M, the electronic configuration becomes 2,5 which is not a stable configuration, Therefore, option (B) is incorrect.
(D) M2- is formed by the addition of 2 electrons to the atom. Then, the electronic configuration becomes 2, 8, 1. This is not a stable configuration. Option (D) is incorrect.
Explanation for correct answer
(C) M- ion is formed by the addition of one electron to the atom. Then the electronic configuration becomes 2, 8. Therefore, the two shells are completely filled and the atom will have a stable configuration. Therefore, M- represents the ion of the metal.
The correct option is (C) M-
M-
Valency
The number of electrons gained or lost by the electron to achieve a stable electronic configuration is called its valency. Atoms form ions by the addition or removal of electrons. The ions formed by the removal of electrons are positive ions and are called cations. The ions formed by the addition of electrons are negatively charged and are called anions. The most stable ion formed by an atom is determined from its number of valence electrons.
A stable configuration is obtained when a shell is completely filled. The ions with the stable configuration will be the stable ion of the element. The maximum occupancy of each shell is in the order 2, 8, 8,18,18,….
The sign on the ion represents whether an electron is added or removed and the magnitude of charge represents the number of electrons added or removed from the atom.
Consider metal M. The number of electrons in the metal is 9. Therefore, its electronic configuration is 2,7.
Explanation for wrong answers
(A) The metal atom contains 7 electrons in the outermost shell. Therefore, the neutral form of the meal does not have complete octet. Therefore, option (A) is incorrect.
(B) M+2 ion is formed by the removal of 2 electrons. When two electrons are removed from M, the electronic configuration becomes 2,5 which is not a stable configuration, Therefore, option (B) is incorrect.
(D) M2- is formed by the addition of 2 electrons to the atom. Then, the electronic configuration becomes 2, 8, 1. This is not a stable configuration. Option (D) is incorrect.
Explanation for correct answer
(C) M- ion is formed by the addition of one electron to the atom. Then the electronic configuration becomes 2, 8. Therefore, the two shells are completely filled and the atom will have a stable configuration. Therefore, M- represents the ion of the metal.
The correct option is (C) M-
