Explanation:
Isobars are atoms of different elements with the same mass number but different atomic numbers. ⁴⁰Ar (atomic number 18) and ⁴⁰Ca (atomic number 20) both have mass number 40. Options A and D are isotopes (same element, different mass number). Option C are isotopes of hydrogen. Isobars have different chemical properties because of different proton numbers. Example: ¹⁴C and ¹⁴N.
Explanation:
The element with atomic number 118 is Oganesson (Og). It is a synthetic element and a member of the noble gas group (Group 18). Ununennium is the temporary name for element 119, Tennessine is 117, and Nihonium is 113.
Explanation:
J.J. Thomson discovered the electron in 1897 through his experiments with cathode ray tubes. He demonstrated that cathode rays were composed of previously unknown negatively charged particles, which were later named electrons. This discovery proved that atoms were not indivisible and led to his 'plum pudding' model.
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