Question

Which of the following statements is correct about isobars?

a) Isobars have different masses but the same atomic number.

b) Isobars have the same mass number but different atomic numbers.

c) Isobars have the same number of electrons in the last orbit.

d) Isobars have the same number of neutrons in the nucleus.

Answer 1

Isobars are species of different elements that have the same mass number but different atomic numbers, meaning they have the same total number of protons and neutrons. The correct answer is option b).

Step-by-step explanation:

The correct statement about isobars is that they have the same mass number but different atomic numbers. Isobars are different atomic species (different elements) that have the same mass number. This means that while their total number of protons and neutrons are equal (adding up to the same mass number).

The number of protons (which defines the atomic number and thus the element) is different for each isobar. For instance, 40Ar (with 18 protons) and 40Ca (with 20 protons) are isobars because they both have a mass number of 40, but their atomic numbers are different, signifying different elements.

This is different from isotopes, which are atoms of the same element with the same number of protons but different numbers of neutrons.