Question

State the number of neutrons in an atom of each of the following isotopes: (a) hydrogen-1 (b) carbon-13 (c) cobalt-59 (d) iodine-127

Short answer

(a) 0 neutrons, (b) 7 neutrons, (c) 32 neutrons, (d) 74 neutrons.

Step-by-step solution

Understand Isotopes and Atomic Structure

An isotope of an element is a variant with the same number of protons but a different number of neutrons. The number of protons (atomic number) for each element is constant and distinct. To find the number of neutrons, subtract the atomic number from the mass number of the isotope.

Determine Atomic Numbers

Find the atomic numbers from the periodic table: - Hydrogen has an atomic number of 1. - Carbon has an atomic number of 6. - Cobalt has an atomic number of 27. - Iodine has an atomic number of 53.

Calculate Neutrons for hydrogen-1

For hydrogen-1: - Mass number = 1 (from the isotope name). - Atomic number = 1. Number of neutrons = Mass number - Atomic number = 1 - 1 = 0 neutrons.

Calculate Neutrons for carbon-13

For carbon-13: - Mass number = 13. - Atomic number = 6. Number of neutrons = Mass number - Atomic number = 13 - 6 = 7 neutrons.

Calculate Neutrons for cobalt-59

For cobalt-59: - Mass number = 59. - Atomic number = 27. Number of neutrons = Mass number - Atomic number = 59 - 27 = 32 neutrons.

Calculate Neutrons for iodine-127

For iodine-127: - Mass number = 127. - Atomic number = 53. Number of neutrons = Mass number - Atomic number = 127 - 53 = 74 neutrons.

Key concepts

Atomic Structure

Atomic structure is the foundation of understanding elements and their behaviors. An atom is made up of three basic particles: protons, neutrons, and electrons.
- **Protons** are positively charged particles found in the atom's nucleus and determine the atomic number of an element.
- **Neutrons** have no charge and are also located in the nucleus, acting as a force to stabilize the atom.
- **Electrons** are negatively charged particles that orbit the nucleus in various energy levels.
The number of protons determines which element the atom represents, and this is unique for each element on the periodic table. Protons and neutrons together make up the atomic nucleus, while electrons spin around the periphery, balancing the positive charge of protons with their negative charge.
Understanding how these components work together is essential for grasping more complex concepts, such as isotopes and atomic weight.

Mass Number

The mass number of an isotope is the sum of its protons and neutrons. Unlike the atomic number, which is constant for each element, the mass number can vary. This variation leads to the existence of isotopes.
Mass number is symbolized as a whole number and is typically located either at the top left of an element symbol or beside the name of the isotope. For instance, in the case of carbon-13, the '13' is the mass number.
This number is critical because it helps us differentiate between isotopes of an element. It gives us the total nucleons in an atom and helps in calculations such as identifying the number of neutrons by subtracting the atomic number from it.
The mass number is important in various scientific calculations, particularly when calculating molar mass and understanding isotope variations across different elements.

Atomic Number

The atomic number is a fundamental concept in chemistry and it defines the identity of an element. It tells us the number of protons in an atom's nucleus. This number is unique for each element and is found on the periodic table.
Because atoms are electrically neutral, the number of electrons in an atom equals the number of protons, making the atomic number also indicative of the electron count.
Elements are arranged on the periodic table in ascending order according to their atomic numbers, which helps in predicting chemical reactivity, bonding patterns, and the placement of elements within periods and groups.
For example, hydrogen, the simplest element, has an atomic number of 1, meaning it has one proton and one electron. This atomic number is crucial for classifying elements and understanding their chemical properties.

Neutrons

Neutrons are one of the main subatomic particles that make up the atomic nucleus along with protons. Unlike protons, neutrons carry no electric charge. Their primary role within the nucleus is to add stability by mediating the repulsive forces between protons, which are positively charged.
The number of neutrons can vary in the atoms of a given element, resulting in different *isotopes*. For example, hydrogen can exist as hydrogen-1, with no neutrons, or as heavier isotopes like deuterium and tritium, which have one and two neutrons respectively.
To find the number of neutrons in an atom, the atomic number (number of protons) is subtracted from the mass number. Neutron count affects the mass and stability of an atom but not its chemical properties.
This variance in neutron number not only leads to different isotopes but can also affect nuclear properties and reactions, making neutrons a vital component to understand in atomic theory.