Home » UPSC NDA-2 » For Aluminium (Al) (atomic number : 13, mass number : 27), which one a

For Aluminium (Al) (atomic number : 13, mass number : 27), which one a

June 1, 2025 by rawan239

For Aluminium (Al) (atomic number : 13, mass number : 27), which one among the following statements is NOT correct ?

Number of electrons present in Al is 13

Number of protons present in Al is 13

Number of neutrons present in Al is 14

The valency of Al is 2

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UPSC NDA-2 – 2024

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For a neutral atom, the number of protons is equal to the atomic number (Z), and the number of electrons is also equal to the atomic number. Given the atomic number of Aluminium (Al) is 13, it has 13 protons and 13 electrons. The mass number (A) is the sum of protons and neutrons. Given the mass number is 27 and the number of protons is 13, the number of neutrons is 27 – 13 = 14. Aluminium is in Group 13 of the periodic table, with electronic configuration 1s² 2s² 2p⁶ 3s² 3p¹. It readily loses its 3 valence electrons to form a stable Al³⁺ ion. Therefore, the typical valency of Aluminium is 3, not 2.

Atomic number = Number of protons. For a neutral atom, Number of electrons = Number of protons. Mass number = Number of protons + Number of neutrons. Valency is related to the number of electrons an atom gains, loses, or shares to form chemical bonds.

Elements in Group 13 (like Aluminium) typically exhibit a valency of +3, forming ions with a +3 charge by losing their three valence electrons.

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