Question

How many protons, neutrons and electrons are in an atom of

a) 138 Ba

Answer 1

A 138 Ba atom consists of 56 protons, 82 neutrons, and 56 electrons.

Explanation

The element symbol "Ba" represents barium, whose atomic number is 56. This atomic number indicates the number of protons in the nucleus. For a 138 Ba isotope, the total number of protons remains the same as the atomic number, so there are 56 protons.

To find the number of neutrons, subtract the atomic number (protons) from the atomic mass. In this case, the atomic mass of 138 Ba is 138. Thus, subtracting 56 protons from the atomic mass gives us 82 neutrons in the nucleus.

Atoms are electrically neutral, so the number of electrons matches the number of protons. With 56 protons, there are also 56 electrons orbiting the nucleus in a stable barium atom. Therefore, a 138 Ba atom consists of 56 protons, 82 neutrons, and 56 electrons, maintaining its overall neutrality and atomic identity.

Answer 2

An atom of 138 Ba has 56 protons, 56 electrons, and 82 neutrons. The atomic number of Ba, which is 56, indicates the number of protons and electrons, while the difference between the mass number (138) and atomic number gives the number of neutrons.

Step-by-step explanation:

The atom in question is barium (Ba) with a mass number of 138. To determine the number of protons, electrons, and neutrons in an atom of 138 Ba, you need to know the atomic number of barium, which represents the number of protons and, in a neutral atom, also the number of electrons. The atomic number of barium (Ba) is 56.

To find the number of neutrons, you subtract the atomic number (protons) from the mass number. Hence:

• Number of protons: 56 (since it is barium)
• Number of electrons: 56 (in a neutral atom, electrons equal protons)
• Number of neutrons: 138 (mass number) - 56 (atomic number) = 8