Question

Which statements about subatomic particles are true? \begin{equation} \begin{array}{l}{\text { a. If an atom has an equal number of protons and electrons, it will be }} \\ {\text { charge-neutral. }} \\ {\text { b. Electrons are attracted to protons. }} \\ {\text { c. Electrons are much lighter than neutrons. }} \\ {\text { d. Protons have twice the mass of neutrons. }}\end{array} \end{equation}

Short answer

Statements a, b, and c are true; electrons are indeed much lighter than neutrons, and an atom is charge-neutral if it has an equal number of protons and electrons, which are attracted to each other. Statement d is false; protons do not have twice the mass of neutrons.

Step-by-step solution

Verification of Statement a

Check if an atom is charge-neutral when it has an equal number of protons and electrons. Protons have a positive charge, while electrons have a negative charge of equal magnitude. An atom with an equal number of protons and electrons will have a net charge of zero because the positive and negative charges will cancel each other out.

Verification of Statement b

Examine the relationship between electrons and protons in terms of attraction. Protons, which are positively charged, and electrons, which are negatively charged, are attracted to each other due to opposite charges, according to Coulomb's law.

Verification of Statement c

Compare the masses of electrons and neutrons. Electrons have a very small mass compared to protons or neutrons. The mass of an electron is about 1/1836 the mass of a proton or neutron, making electrons much lighter than neutrons.

Verification of Statement d

Assess whether protons have twice the mass of neutrons. Protons and neutrons have masses that are extremely close to each other, but not in a double relationship. Neutrons are slightly heavier than protons, but not to the extent that protons are half the mass of neutrons.

Key concepts

Atomic Structure

The atomic structure is fundamental to understanding the behavior and characteristics of elements. At the center of an atom lies the nucleus, which contains two of the main subatomic particles: protons and neutrons. Protons carry a positive electrical charge, while neutrons are neutral, hence their name.

Electrons, the third type of subatomic particle, orbit the nucleus in various energy levels or shells. These electrons are negatively charged and are crucial in the formation of chemical bonds. It's this arrangement of protons, neutrons, and electrons that defines the atom's properties and its place in the periodic table of elements.

Understanding the arrangement of these subatomic particles is key in chemistry and physics, as it determines how atoms interact with each other, form molecules, and participate in chemical reactions.

Charge Neutrality

Charge neutrality is a fundamental concept of chemistry and physics, explaining that atoms have no overall electrical charge when they possess an equal number of protons and electrons. As mentioned in the solution to our example exercise, protons have a positive charge and electrons have an identical but negative charge.

When an atom has an equal number of both, the positive and negative charges balance out, resulting in a neutral charge. This balance is what makes the bulk of the matter we interact with in our daily lives non-reactive and stable. In contrast, ions, which are atoms or molecules with an unequal number of protons and electrons, are charged and more chemically reactive.

Electron Mass

The electron is minuscule compared to protons or neutrons, having a mass approximately 1/1836th that of a proton, as noted in the exercise solution. While the mass of an electron is incredibly small (\(9.109 \times 10^{-31}\text{ kilograms}\)), it plays a significant role in the physical and chemical properties of atoms.

For instance, an electron's mass affects its motion around the nucleus and its energy levels, thereby influencing the atom's chemical behavior. Despite being lightweight, electrons are instrumental in electrical conductivity, chemical bonding, and magnetic properties. Having precise knowledge about electron mass is crucial for understanding how atoms absorb and emit light, allowing scientists to develop technologies such as lasers and LEDs.

Proton-Neutron Mass

Contrary to what some might think, protons and neutrons do not have drastically different masses. In fact, they are quite similar, though neutrons are slightly heavier. The statement suggesting that protons have half the mass of neutrons is incorrect.

The small difference in mass between protons and neutrons is essential for nuclear stability. Neutrons play a critical role in the nucleus by mediating the strong nuclear force that holds the nucleus together, overcoming the repulsive force between positively charged protons. Their near-equal mass also means that during certain radioactive decay processes, such as beta decay, a neutron can transform into a proton and vice versa, changing the identity of the element.