Question

Which of the following have the same charge and approximately the same mass? (a) an electron and a proton; (b) a proton and a neutron; (c) a hydrogen atom and a proton; (d) a neutron and a hydrogen atom; (e) an electron and an \(\mathrm{H}^{-}\) ion.

Short answer

(b) Proton and neutron share approximately the same mass. (c) Hydrogen atom and Proton share approximately the same mass. (d) Neutron and hydrogen share approximately the same mass. None share the same charge and the same mass.

Step-by-step solution

Evaluate (a) An Electron and a Proton

An electron has a negative charge while a proton has a positive charge. In terms of mass, the proton is nearly 2000 times heavier than the electron. Thus, they do not have same charge or same mass.

Evaluate (b) A Proton and a Neutron

A proton carries a positive charge, whereas a neutron is neutral. In terms of mass, both have approximately the same mass, as they exist in the nucleus of an atom. We could say that they have same mass but not the same charge.

Evaluate (c) A Hydrogen Atom and a Proton

A hydrogen atom consists of a proton and an electron and is neutral while a proton carries a positive charge. In terms of the mass, a hydrogen atom is approximately equal in mass to a proton since the mass of an electron is nearly negligible. They do not have the same charge, but they have similar mass.

Evaluate (d) A Neutron and a Hydrogen Atom

A neutron is neutral while a hydrogen atom, which consists of a proton and an electron, is also overall neutral. In terms of mass, a hydrogen atom is approximately equal to a neutron, as the electron's mass is nearly negligible. Thus, they do not share the same charge, but have similar mass.

Evaluate (e) An Electron and an \(\mathrm{H}^{-}\) Ion

An electron carries a negative charge while an \(\mathrm{H}^{-}\) ion also has a negative charge because it's a hydrogen atom that gained an extra electron. However, the \(\mathrm{H}^{-}\) ion is heavier than an electron as it consists of a proton, neutron and an extra electron. Therefore, they do share the same charge, but have different masses.

Key concepts

Electron

Electrons play a critical role in the substructure of atoms. They are subatomic particles with a negative electric charge and negligible mass compared to protons and neutrons. This negative charge is fundamental, balancing the positive charge of protons to form neutral atoms.
Electrons are located in orbitals surrounding the atom's nucleus. They are responsible for the formation of chemical bonds and electricity flow.
It's important to know:

• An electron's charge is -1 e (elementary charge).
• The mass of an electron is approximately 9.11 x 10^{-31} kg.
• In ions, electrons can be gained or lost, which changes the charge but not significantly the mass of the ion.

Neutron

Neutrons are one of the building blocks of atomic nuclei. They are subatomic particles with no electric charge, hence the name 'neutral'. While neutrons and protons form the atom's nucleus, their main role is providing stability to the nucleus by spacing out the positively charged protons and allowing them to coexist.
Key points to remember about neutrons:

• Neutrons have approximately the same mass as protons, about 1.675 x 10^{-27} kg.
• They do not have any charge, making them neutral particles.
• Neutrons are essential for the nuclear chain reactions in fission processes.

Hydrogen Atom

The simplest and most abundant element in the universe, hydrogen, is composed of one proton, one electron, and in some isotopes, one neutron. The structure of a hydrogen atom is crucial in understanding atomic theory as it forms the basis for more complex elements.
Here are some characteristics of a hydrogen atom:

• A neutral hydrogen atom consists of one proton and one electron.
• It can exist as an ion, such as \( ext{H}^{-}\), when an extra electron is added.
• The mass of a hydrogen atom is mostly due to the proton, as the electron's mass is negligible.

Charge

Charge is a fundamental property of matter, defining the electromagnetic interactions between particles. It is an intrinsic characteristic of elementary particles like electrons and protons, dictating their attraction or repulsion.
It's measured in coulombs (C) and is responsible for creating electric fields.

• Electrons carry a negative charge, approximately -1.6 x 10^{-19} C.
• Protons carry a positive charge, equal in magnitude but opposite to the electron's charge.
• Charges can be transferred through chemical and physical processes, leading to ion formation.

Mass

Mass is a measure of the amount of matter in a particle or object, often confused with weight, but distinctive in that it remains constant regardless of location. In the context of subatomic particles:

• Protons and neutrons have nearly the same mass, giving most of the mass to the atom.
• An electron's mass is significantly smaller, often considered negligible in mass calculations.
• Mass conservation is key in physical reactions ensuring the sum of masses in reactants equals the sum in products.

Understanding mass is crucial in physics and chemistry for the stoichiometric calculations and dynamic processes.