What is the number of neutrons in atoms of the following isotopes: 15N, 119SN, 235U

Isotopes in chemistry mean atoms of the same chemical element, which have different atomic masses due to the different number of neutrons in the nucleus. Neutrons have virtually no effect on the chemical properties of an element, unlike protons. Therefore, each element can have several isotopes with the same number of protons, but different numbers of neutrons.

Let’s calculate the number of neutrons for the nitrogen-15 isotope.

Nitrogen in the periodic table is at number 7. This means that the atom in the ground state has 7 electrons and exactly the same number of protons in the nucleus. The 15N isotope has a relative atomic mass of 15. So the total number of neutrons and protons in the nucleus is 15. Find the number of neutrons:

N = 15 – 7 = 8

The 15N isotope has 8 neutrons in its nucleus

Let’s calculate the number of neutrons for the 119Sn isotope.

Tin in the periodic system is numbered 50, which means that an atom contains 50 electrons and 50 protons. Relative atomic mass = 119

N = 119 – 50 = 69

The 119Sn isotope has 69 neutrons in its nucleus.

Let’s calculate the number of neutrons for the isotope 235U.

Uranium in the periodic system with number 92. So the number of electrons = the number of protons = 92. The relative atomic mass of the isotope = 235.

N = 235 – 92 = 143

The isotope 235U contains 143 neutrons in the nucleus.