The nucleus of a hydrogen  atom consist of a?

Analysis

The question asks for the subatomic composition of the nucleus of a standard hydrogen atom. To answer this, we must look at the atomic structure of the most common isotope of hydrogen, known as Protium ($^1_1H$).

Concept

• Atomic Structure: An atom consists of a central nucleus containing protons and neutrons, surrounded by electrons in shells.
• Hydrogen Atom: Hydrogen is the simplest element in the periodic table. Its atomic number is 1, which means it has 1 proton. Its mass number is also 1.
• The Nucleus: The mass number is the sum of protons and neutrons. Since the mass number is 1 and the number of protons is 1, the number of neutrons must be $1 - 1 = 0$.
• Electrons: Electrons are found outside the nucleus, not inside it.

Step-by-Step Solution

1. Identify the Atomic Number ($Z$): For hydrogen, $Z = 1$. This confirms there is 1 proton.
2. Identify the Mass Number ($A$): For the most common hydrogen atom, $A = 1$.
3. Calculate Neutrons ($N$): Using the formula $N = A - Z$, we get $N = 1 - 1 = 0$. Therefore, there are no neutrons in the nucleus of a standard hydrogen atom.
4. Evaluate the Options: • A: 1 proton only — This is correct because there are no neutrons and the electron is outside the nucleus. • B: 1 proton, 2 neutrons — This describes Tritium, a radioactive isotope of hydrogen, not the standard hydrogen atom. • C: 1 neutron only — Incorrect; hydrogen has no neutrons in its nucleus. • D: 1 electron only — Incorrect; electrons are located in the orbital shells, not the nucleus.

Conclusion

The nucleus of a standard hydrogen atom consists solely of a single proton.

Exam Tip

Remember the acronym PEN: Protons and Electrons are equal in a neutral atom, but Neutrons are calculated by subtracting the atomic number from the mass number. For hydrogen, the "N" is zero, making it the only element in the periodic table without a neutron in its nucleus!