The highest isotope of hydrogen is

Analyze the question: "Highest isotope of hydrogen" is asking which isotope has the greatest mass number, meaning the most neutrons.

Explain the concept: Isotopes are atoms of the same element with the same number of protons (same atomic number) but different numbers of neutrons. Hydrogen has three common isotopes:

| Isotope | Symbol | Protons | Neutrons | Mass number | |---|---|---|---|---| | Protium | ¹H | 1 | 0 | 1 | | Deuterium | ²H (D) | 1 | 1 | 2 | | Tritium | ³H (T) | 1 | 2 | 3 |

Solution:

• Protium has mass number 1 (lightest, most abundant).
• Deuterium has mass number 2.
• Tritium has mass number 3, so it is the heaviest, or "highest", isotope.
• Positron is not an isotope of hydrogen at all. It is the antiparticle of the electron (a positively charged beta particle, ⁰₊₁e).

Answer: The highest isotope of hydrogen is tritium, which is option C.

Exam tip: Remember the order of the hydrogen isotopes by their prefixes: Protium (1), Deuterium (2, like "duo"), Tritium (3, like "tri" meaning three). The prefix tells you the mass number: protium = first, deuterium = second, tritium = third. Tritium is also radioactive, which JAMB sometimes tests.