Q.Answer the following question.
Define the terms:
i. Isotones ii. Isoelectronic species iii. Electronic configuration

Isotopes have the same atomic number but different mass numbers (different neutron counts); hydrogen's neutron-free isotope is protium.

Isotopes are atoms of the same element that have the same atomic number (Z, i.e. the same number of protons, and hence the same number of electrons and identical chemical properties) but different mass numbers (A), because they contain different numbers of neutrons.

Hydrogen has three well-known isotopes:

• Protium, ¹₁H — 1 proton, 0 neutrons.
• Deuterium, ²₁H (D) — 1 proton, 1 neutron.
• Tritium, ³₁H (T) — 1 proton, 2 neutrons. …

Hydrogen has three isotopes -- Protium, Deuterium, Tritium -- differing only in neutron number; Protium (1H1) has no neutron at all.

Isotopes are atoms of the same element (same number of protons/atomic number) that differ in the number of neutrons, and hence in mass number. Hydrogen (Z=1) has three naturally occurring isotopes:

1. Protium (1H1): 1 proton, 0 neutrons -- the most common form of hydrogen (about 99.98% abundance).
2. Deuterium (1H2, symbol D): 1 proton, 1 neutron.
3. Tritium (1H3, symbol T): 1 proton, 2 neutrons (radioactive). …

Isotopes are atoms of the same element with identical atomic number (same number of protons) but different mass numbers (different number of neutrons). Hydrogen has three isotopes: protium, deuterium and tritium.

Isotopes are atoms of the same chemical element that have the same atomic number (same number of protons, and hence the same number of electrons and identical chemical properties) but different mass numbers, because they contain different numbers of neutrons in the nucleus.

The three isotopes of hydrogen:

1. Protium (1H1 or 1H) - the ordinary, most abundant form of hydrogen, with 1 proton and 0 neutrons.
2. Deuterium (2H1, symbol D) - also called heavy hydrogen, with 1 proton and 1 neutron.
3. Tritium (3H1, symbol T) - a radioactive isotope, with 1 proton and 2 neutrons. …