2018 · Q31
Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40?
General KnowledgeChemistry
- AElement with 20 protons and 18 neutrons
- BElement with 18 protons and 19 neutrons
- CElement with 20 protons and 19 neutrons
- DElement with 18 protons and 22 neutrons
Explanation
Isobars are atoms with the same mass number. Calcium's mass number here is 40, so its isobar must also total 40 nucleons. An element with 18 protons and 22 neutrons has mass number 18 + 22 = 40, while the other options give 38, 37 and 39. Hence the answer is the element with 18 protons and 22 neutrons.