Question

Each of the following isotopes is used in medicine. Indicate the number of protons and neutrons in each isotope: (a) phosphorus-32, (b) chromium- 51, (c) cobalt- 60 , (d) technetium-99, (e) iodine-131; (f) thallium-201.

Short answer

The isotopes have the following numbers of protons and neutrons: a) Phosphorus-32: 15 protons, 17 neutrons b) Chromium-51: 24 protons, 27 neutrons c) Cobalt-60: 27 protons, 33 neutrons d) Technetium-99: 43 protons, 56 neutrons e) Iodine-131: 53 protons, 78 neutrons f) Thallium-201: 81 protons, 120 neutrons

Step-by-step solution

Identify the element and its atomic number

To determine the number of protons in an isotope, we need to identify the element and its atomic number. You can use the periodic table to find the atomic number of each element. Here's the atomic number for each element given in the problem: a) Phosphorus (P) - Atomic number: 15 b) Chromium (Cr) - Atomic number: 24 c) Cobalt (Co) - Atomic number: 27 d) Technetium (Tc) - Atomic number: 43 e) Iodine (I) - Atomic number: 53 f) Thallium (Tl) - Atomic number: 81

Determine the number of protons

The number of protons in an isotope is equal to the atomic number of the element. So, the number of protons for each isotope is: a) Phosphorus-32: 15 protons b) Chromium-51: 24 protons c) Cobalt-60: 27 protons d) Technetium-99: 43 protons e) Iodine-131: 53 protons f) Thallium-201: 81 protons

Determine the number of neutrons

To find the number of neutrons, we'll subtract the atomic number from the isotope's mass number. The mass numbers are given in the problem (32, 51, 60, 99, 131, and 201). So the number of neutrons is: a) Phosphorus-32: \(32-15=17\) neutrons b) Chromium-51: \(51-24=27\) neutrons c) Cobalt-60: \(60-27=33\) neutrons d) Technetium-99: \(99-43=56\) neutrons e) Iodine-131: \(131-53=78\) neutrons f) Thallium-201: \(201-81=120\) neutrons So, the isotopes have the following numbers of protons and neutrons: a) Phosphorus-32: 15 protons, 17 neutrons b) Chromium-51: 24 protons, 27 neutrons c) Cobalt-60: 27 protons, 33 neutrons d) Technetium-99: 43 protons, 56 neutrons e) Iodine-131: 53 protons, 78 neutrons f) Thallium-201: 81 protons, 120 neutrons

Key concepts

Atomic Number

Every element on the periodic table has its own unique atomic number. This number is extremely important because it tells you how many protons are found in the nucleus of an atom of that element. The atomic number is like an element's ID number. When you know it, you can find the element’s position on the periodic table.
Take phosphorus for example, with an atomic number of 15. This means every atom of phosphorus has 15 protons inside its nucleus. Similarly, other elements have their own number of protons, like chromium with 24, and iodine with 53. Knowing the atomic number also helps us to easily determine which element we are dealing with in chemical reactions or when studying isotopes.

Protons

Protons are positively charged particles located in the nucleus at the center of an atom. These little particles are extremely important because they define what element you're dealing with. The number of protons is not only equal to the atomic number, but it's also what keeps the electrons in orbit around the nucleus.

• Protons have a positive charge, which balances the negative charge of electrons in a neutral atom.
• They also play a major part in the mass of an atom, even though they are tiny in size.

For instance, an atom of cobalt has 27 protons. This number doesn't change, even in different isotopes of cobalt, like cobalt-60, which is used in medical treatments.

Neutrons

Neutrons share the nucleus with protons but are a bit different. They have no electric charge, which is why they're called 'neutrons.' Neutrons are important because they add mass to an atom and play a role in nuclear stability. In isotopes, the number of neutrons can vary, which is why isotopes can have different mass numbers.
To find the number of neutrons in an isotope, you subtract the atomic number (number of protons) from the mass number of the isotope. For example:

• In the isotope phosphorus-32, there are 17 neutrons, calculated as: 32 (mass number) - 15 (atomic number).
• In iodine-131, there are 78 neutrons: 131 (mass number) - 53 (atomic number).

Neutrons help to make up the atom's mass but because they are neutral, they don't affect the charge of the atom.

Mass Number

The mass number of an element gives you a sense of its heft. It's the total number of protons and neutrons in an atom's nucleus. Remember, electrons are so small that they don't significantly contribute to an atom's mass. By knowing the mass number, you can know more about an isotope of an element.
Here’s how you do it:

• Take the mass number of technetium-99, for example, and subtract the atomic number (43 protons) to find it has 56 neutrons.
• Each isotope is recognized by its mass number, like chromium-51 or thallium-201.

This number helps you understand the isotopic differences in elements, especially useful in distinguishing isotopes for medicinal use.

Periodic Table

The periodic table is a marvelous tool for anyone studying chemistry. It's like a map that displays all known elements in an organized way. Each element is placed in order of increasing atomic number, which defines its position.

• Elements in the same column, or group, often share similar characteristics.
• You'll find metals, nonmetals, and metalloids all categorized across its neatly arranged rows and columns.

For example, you can quickly find chromium by its atomic number, 24, and know it’s a transition metal. Isotopes like phosphorus-32 or cobalt-60 can be traced back to their respective elements by referring to this table. This makes it an indispensable reference in both education and research.