A subatomic particle has four times the mass of a proton and twice its positive charge. Which particle fits this description most accurately?

Introduction / Context:
Understanding the basic nuclear and subatomic particles is an important part of general physics and chemistry. Protons, neutrons, electrons, alpha particles and other nuclei all differ in mass and charge. Many multiple choice questions ask you to compare particles using simple ratios of mass and charge. In this problem, we are told that an unknown particle has four times the mass of a proton and twice its positive charge, and we must identify which named particle matches that description.

Given Data / Assumptions:

• Reference particle: proton with charge +1 and mass approximately 1 atomic mass unit.
• Unknown particle: mass is four times proton mass and charge is +2 relative to the proton.
• Options include helium atom, alpha particle, deuteron and tritium nucleus, plus a positron.
• We assume approximate masses and charges as taught at school level.

Concept / Approach:
An alpha particle is the nucleus of a helium atom. It contains two protons and two neutrons. Therefore, its charge is +2 (due to the two protons) and its mass is approximately 4 atomic mass units (two protons plus two neutrons). A deuteron is the nucleus of heavy hydrogen with one proton and one neutron, so its mass is about 2 units and its charge is +1. A tritium nucleus has one proton and two neutrons, giving a mass of about 3 units and charge +1. A helium atom includes two electrons and has net charge zero. A positron has the same mass as an electron, far smaller than a proton, and charge +1. Only the alpha particle has both mass about 4 and charge +2.

Step-by-Step Solution:
Step 1: Note that the unknown particle must have charge +2, which eliminates neutral atoms and particles with charge +1 or 0.Step 2: A helium atom has two protons and two electrons, so its net charge is zero, not +2.Step 3: A deuteron has charge +1 and mass about 2, so it does not match either the charge or mass given.Step 4: A tritium nucleus has charge +1 and mass about 3, still not equal to four times the proton mass or double its charge.Step 5: A positron has the same small mass as an electron and therefore cannot have four times the proton mass.Step 6: An alpha particle (helium nucleus) has two protons and two neutrons, so its mass is approximately 4 and its charge is +2.Step 7: Conclude that the particle described must be an alpha particle.

Verification / Alternative check:
You can check by recalling nuclear notation. The alpha particle is written as 4 2 He, where the top number 4 is the mass number and the bottom number 2 is the atomic number, which equals the charge in units of the proton charge. The proton is 1 1 H. Comparing these shows directly that the alpha particle has four times the mass number and twice the charge of the proton, matching the description in the question perfectly.

Why Other Options Are Wrong:
Option a, helium atom, is electrically neutral because the two positive charges of the protons are balanced by two electrons. Option c, deuteron, has charge +1 and mass 2, not mass 4 and charge +2. Option d, tritium nucleus, has mass 3 and charge +1, again not matching the required ratios. Option e, positron, has mass much smaller than the proton and cannot be four times heavier. Only the alpha particle fits both the mass and charge conditions together.

Common Pitfalls:
A common mistake is to confuse the helium atom with the helium nucleus. Although they involve the same element, the neutral atom has electrons and therefore net charge zero, while the alpha particle is just the nucleus with a net positive charge. Another pitfall is to remember only the mass or only the charge and not both. The question clearly specifies two ratios, and the correct answer must satisfy both at the same time.

Final Answer:
The particle with four times the mass of a proton and twice its positive charge is an alpha particle, the helium nucleus.