Question

Cobalt (Co) has an atomic mass of 59 and an atomic number of 27. Which statement correctly describes an atom of cobalt?

O A. An atom of cobalt contains more neutrons than protons.
B. An atom of cobalt contains more electrons than protons.
O C. An atom of cobalt contains the same number of neutrons and protons.
O D. An atom of cobalt contains the same number of neutrons, electrons and protons.

Answer 1

Option A. An atom of cobalt contains more neutrons than protons.

Step-by-step explanation:

From the question given above, the following data were obtained:

Mass number = 59

Atomic number = 27

Next, we shall determine the number of protons in the atom. This is illustrated below:

Atomic number of an element is simply defined as the number of protons in the atom of the element. Thus,

Atomic number = proton number

Atomic number = 27

Therefore,

Proton number = 27

Next, we shall determine the neutron number. This can be obtained as follow:

Mass number = 59

Proton number = 27

Neutron number =?

Mass number = Proton + Neutron

59 = 27 + Neutron

Collect like terms

Neutron = 59 – 27

Neutron number = 32

Next, we shall determine the number of electrons. This can be obtained as follow:

Since the atom is neutral i.e it has no charge, then, the number of protons and electrons are equal. Thus,

Electron number = Proton number

Proton number = 27

Therefore,

Electron number = 27

Summary:

Mass number = 59

Atomic number = 27

Proton number = 27

Neutron number = 32

Electron number = 27

From the above, we can see that the atom of cobalt contains:

1. More neutrons than protons.

2. The same number of protons and electrons.

Therefore, option A gives the correct answer to the question.