Question

In which of the following is number of electrons the ion contains given correctly? A. H+ has 1 electron. B. Br- has 34 electrons. C. Al3+ has 16 electrons. D. Ca2+ has 18 electrons

Answer 1

The correct answer would be D. Ca^2+ has 18 electrons. This is because 2+ means that 2 electrons have been removed, and Ca starts out with 20 electrons. As 20 - 2 = 18 electrons, D is the correct answer.

Hope this helps!

Answer 2

Answer: The correct answer is Option D.

Explanation:

Number of electrons that are present in an atom is determined by the electronic configuration of that atom.

If an ion is carrying a positive charge, it means that the atom has lost electrons and if an ion is carrying a negative charge, it means that the atom has gained electrons.

For the given options:

Option A: The atomic number of hydrogen atom is 1 and the electronic configuration for $H^+$ ion will be: $1s^0$

Thus, this atom does not have any electrons.

Option B: The atomic number of bromine atom is 35 and the electronic configuration for $Br^-$ ion will be: $1s^22s^22p^63s^23p^64s^23d^{10}4p^6$

Thus, this atom has 36 electrons.

Option C: The atomic number of aluminium atom is 13 and the electronic configuration for $Al^{3+}$ ion will be: $1s^22s^22p^6$

Thus, this atom has 10 electrons.

Option D: The atomic number of calcium atom is 20 and the electronic configuration for $Ca^{2+}$ ion will be: $1s^22s^22p^63s^23p^6$

Thus, this atom has 18 electrons.

Hence, the correct answer is option D.