Concept explainers
Which of the following statements about the mass number of an atom is incorrect?
a. It has a unit defined as a dalton.
b. On Earth, it equals the atomic weight.
c. Unlike the atomic weight of an atom, it does not change when gravitational forces change.
d. It equals the number of electrons in an atom.
e. It is the sum of the protons and neutrons in the atomic nucleus.
Introduction:
The elements are made up one type of atoms which contain electrons, protons, and neutrons. The atoms contain a nucleus, which contains protons and neutrons in it. The electrons revolve around the nucleus in their orbital paths. The atomic number of an element is the total number of protons present in the nucleus.
Answer to Problem 1TYK
Correct answer:
It equals the number of electrons in an atom.
Explanation of Solution
Justification for the correct answer:
Option (d) is that it equals the number of electrons in an atom. The mass number is represented by the sum of protons and neutrons. It is taken so because the mass of a proton and a neutron is almost equal, which is
Justification for the incorrect answers:
Option (a) is that its unit is Dalton. The mass of proton and neutron is given by a unit named Dalton (Da). So, it is an incorrect option.
Option (b) is that on earth, it equals its atomic weight. The atomic mass is called Atomic weight if the gravitational force is considered. The mass number equals atomic weight when it is affected by the Earth’s gravitational force. So, it is an incorrect option.
Option (c) is that unlike the atomic weight of an atom, it does not change when gravitational forces change. The weight changes with a change in gravitational force but the mass is not changed. So, it is an incorrect option.
Option (e) is that it is the sum of the protons and neutrons in the atomic nucleus. The atomic nucleus contains neutron and protons, whose summation gives the mass number. So, it is an incorrect option.
Hence, options (a), (b), (c) and (e) are incorrect.
Thus, it can be concluded that the mass number is independent of the number of electrons contained in an atom. It is equal to the sum of the number of protons and neutrons in the atomic nucleus.
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Chapter 2 Solutions
Biology: The Dynamic Science (MindTap Course List)
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