Question

In which one of the following pairs the two species are both isoelectronic and isotopic?
(Atomic numbers : Ca = 20, Ar = 18, K = 19, Mg = 12, Fe = 26, Na = 11)
(a) ⁴⁰Ca²⁺ and ⁴⁰Ar
(b) ³⁹K⁺ and ⁴⁰K⁺
(c) ²⁴Mg²⁺ and ²⁵Mg
(d) ²³Na and ²⁴Na⁺

Answer 1

The correct option is b) 39K+ and 40K+

Reason: The species (molecules, atoms or ions) containing same number of electrons are called isoelectronic species.

Atomic number of potassium is 19 so number of electron in 39K+ and 40K+ is 18. So both are isoelectronic species.

Isotopes are defined as atoms of same element having the same atomic number, but different mass numbers. These atoms contain an equal number of protons and electrons, but a different number of neutrons.

The number of neutron in 39K+ and 40K+ is 20 and 21 respectively and have same atomic number i.e., 19 so both are isotopes.

Answer 2

Answer:

b is correct

Explanation:

because isoelectronic species mean same element, same atomic no. , and different atomic mass no.

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