Question

State the number of neutrons in an atom of each of the following isotopes: (a) hydrogen-2 (b) carbon-14 (c) \(\operatorname{cobalt}-60\) (d) iodine-131

Short answer

(a) 1 neutron, (b) 8 neutrons, (c) 33 neutrons, (d) 78 neutrons

Step-by-step solution

Understanding Isotopes

Every isotope of an element contains the same number of protons but a different number of neutrons. The number of protons in an atom is also known as its atomic number, while the mass number of an isotope is the sum of its protons and neutrons.

Determine Number of Protons

Determine the number of protons for each element based on its atomic number: (a) Hydrogen has 1 proton. (b) Carbon has 6 protons. (c) Cobalt has 27 protons. (d) Iodine has 53 protons.

Calculate the Number of Neutrons

To find the number of neutrons, subtract the number of protons from the mass number of each isotope: (a) For hydrogen-2: Neutrons = 2 - 1 = 1 (b) For carbon-14: Neutrons = 14 - 6 = 8 (c) For cobalt-60: Neutrons = 60 - 27 = 33 (d) For iodine-131: Neutrons = 131 - 53 = 78

Key concepts

Neutrons

Neutrons are neutral particles found within the nucleus of an atom. Unlike protons and electrons, neutrons do not have an electrical charge. They play a key role in the stability of atoms. The number of neutrons can vary in the atoms of the same element, leading to different isotopes. This is possible because while the number of protons in a given element's atoms remains constant, neutrons can change, affecting the isotope's mass number without altering its chemical properties significantly. To determine the number of neutrons in an isotope, you can use the formula: - Neutrons = Mass Number - Atomic Number For example, in the isotope carbon-14, where the mass number is 14 and carbon has 6 protons (its atomic number), it has: - Neutrons = 14 - 6 = 8, indicating there are 8 neutrons present in the atom of this isotope.

Atomic Number

The atomic number is a fundamental property of an element. It represents the number of protons found in the nucleus of an atom of that element. Each element on the periodic table has a unique atomic number, which makes it distinct from other elements. For example, hydrogen has an atomic number of 1 because it has one proton. Carbon, with an atomic number of 6, has six protons. - The atomic number is crucial as it defines the identity of an element. - Elements with different atomic numbers have different chemical properties. Knowing the atomic number of an element helps you understand not just the number of protons, but also its place in the periodic table and thus its behavior in chemical reactions.

Mass Number

Mass number is the total count of protons and neutrons in the nucleus of an atom. While the atomic number tells you how many protons there are, the mass number gives a more comprehensive view by including neutrons.When you see an isotope like iodine-131, "131" is the mass number.- Formulated as: \ \[ \text{Mass Number} = \text{Protons} + \text{Neutrons} \]Mass number plays a critical role in identifying isotopes, as isotopes have the same atomic number but different mass numbers due to variations in the neutron count.- This affects the atomic mass of isotopes and is especially important in fields like nuclear physics where such variations determine the isotope's stability and behavior.