Problem 22 - Chemistry: The Central Science in SI Units, Global Edition

Question

Determine whether each of the following statements is true or false. If false, correct the statement to make it true: (a) The nucleus has most of the mass and comprises most of the volume of an atom. (b) Every atom of a given element has the same number of protons. (c) The number of electrons in an atom equals the number of neutrons in the atom. (d) The protons in the nucleus of the helium atom are held together by a force called the strong nuclear force.

Step-by-Step Solution

Answer

(a) False. Corrected statement: The nucleus has most of the mass but occupies a tiny fraction of the volume of an atom. (b) True. (c) False. Corrected statement: The number of electrons in a neutral atom equals the number of protons in the atom. (d) True.

Step 1: Statement (a)

The nucleus has most of the mass and comprises most of the volume of an atom. This statement is false. The nucleus does contain most of the mass of an atom, but it occupies only a tiny fraction of the atom's volume. Corrected statement: The nucleus has most of the mass but occupies a tiny fraction of the volume of an atom.

Step 2: Statement (b)

Every atom of a given element has the same number of protons. This statement is true. The number of protons in an atom is called the atomic number and it determines which element the atom belongs to. Atoms of the same element will always have the same number of protons.

Step 3: Statement (c)

The number of electrons in an atom equals the number of neutrons in the atom. This statement is false. The number of electrons in a neutral atom equals the number of protons, and the number of neutrons in an atom is independent of the number of electrons or protons. Neutrons and protons both contribute to the mass of an atom, but they are not necessarily equal in number. Corrected statement: The number of electrons in a neutral atom equals the number of protons in the atom.

Step 4: Statement (d)

The protons in the nucleus of the helium atom are held together by a force called the strong nuclear force. This statement is true. The strong nuclear force (also known as the strong force or strong interaction) is the force that binds protons and neutrons together in the nucleus of an atom. It is much stronger than the electrostatic force that would otherwise cause protons to repel each other due to their positive charge, but its range is limited to the size of an atomic nucleus. As a result, it is responsible for holding the protons together within the nucleus.

Key Concepts

Nucleus

The nucleus is a tiny, dense region located at the center of an atom. Despite occupying only a minuscule portion of an atom's volume, it contains most of the atom's mass. This is because the nucleus houses both protons and neutrons, which are much heavier than electrons.
The small volume of the nucleus compared to the entire atom is due to the vast space surrounding it, where the electrons reside. This vast space is mostly empty, giving the atom its size, but not contributing significantly to its mass.

• The nucleus is held together by the strong nuclear force, a fundamental force that will be discussed later.
• It is responsible for the atom's overall positive charge due to the presence of protons.

Protons

Protons are positively charged particles found within the nucleus of an atom. Each element is defined by the number of protons present. This number is known as the atomic number. For example, all carbon atoms have 6 protons, which is what makes them carbon. The atomic number not only identifies the element but also determines its properties.
Protons contribute to the mass of the atom alongside neutrons. Their positive charge is what influences the behavior and arrangement of electrons around the nucleus. The number of protons remains consistent for each element under normal conditions.

• Protons are crucial in determining the identity of an element.
• They play a key role in the nuclear force that keeps the nucleus intact.

Electrons

Electrons are negatively charged particles that orbit the nucleus in regions called electron clouds or shells. They are significantly lighter than protons or neutrons, which is why they contribute negligibly to the overall mass of the atom.
In a neutral atom, the number of electrons equals the number of protons, balancing the positive charge of the protons with their negative charge. Electrons are constantly moving and are found at varying distances from the nucleus, which contributes to the atom's shape and volume.

• Electrons are responsible for the chemical properties of atoms and how they interact with other atoms.
• They can be transferred or shared between atoms, leading to the formation of bonds and compounds.

Strong Nuclear Force

The strong nuclear force is one of the four fundamental forces in nature. It is responsible for holding the nucleus together by overcoming the repulsive electrostatic force between positively charged protons.
Despite the immense strength of the strong nuclear force, it operates only over very short distances, roughly the size of the nucleus. This property ensures that protons (and neutrons) remain tightly packed within the nucleus, without flying apart due to repulsion.

• The strong nuclear force plays a key role in the stability of the nucleus, especially in larger atoms.
• It is much stronger than both gravity and electromagnetic forces within the nucleus, but only at subatomic distances.