Question

What atom has only one proton? a. hydrogen c. a free radical b. an isotope d. a radioisotope

Short answer

The atom with only one proton is hydrogen.

Step-by-step solution

Identify the Atom

We need to identify which atom has only one proton. The number of protons is crucial because it defines the atomic number, which in turn defines the element.

Analyze the Options

Look at the provided options: a. hydrogen b. an isotope c. a free radical d. a radioisotope.

Determine the Atomic Number

Recall that hydrogen is the first element in the periodic table with an atomic number of 1. This means hydrogen has exactly one proton.

Examine the Other Terms

An isotope is an atom of the same element with different numbers of neutrons, not protons. A free radical is an atom or molecule with an unpaired electron, unrelated to the number of protons. A radioisotope is a radioactive isotope of an element, which can have any number of protons depending on the element.

Select the Correct Answer

Since hydrogen is the only element with exactly one proton, option a, hydrogen, is the correct choice.

Key concepts

Protons

Protons are fundamental particles found in the nucleus of every atom. They carry a positive charge, making them essential for defining the identity of an element. The number of protons in an atom's nucleus is known as the atomic number. This number is the deciding factor for determining what element the atom is. For example, if an atom has only one proton, it must be hydrogen, because hydrogen is the first element in the periodic table with an atomic number of 1.

• Protons have a relative mass of 1 atomic mass unit (amu).
• They help keep the nucleus together along with neutrons.
• The positive charge of protons balances the negative charge of electrons in a neutral atom.

Understanding the role of protons is crucial for studying chemistry and atomic theory, as they play a key part in determining an element's properties and place in the periodic table.

Hydrogen

Hydrogen is the simplest and lightest element on the periodic table, represented by the symbol 'H'. It is unique because it consists of only one proton and one electron, with no neutrons in its most common form. This simplicity is why it's the first element listed in the periodic table. Hydrogen is abundant both on Earth and throughout the universe. It is a major component of water (H₂O) and organic compounds, playing vital roles in chemical reactions and life processes.

• Hydrogen gas (H₂) is colorless, tasteless, and highly flammable.
• It serves as the primary fuel for the sun through nuclear fusion.
• Hydrogen has three isotopes: protium, deuterium, and tritium.

Each hydrogen isotope varies by the number of neutrons but retains the single proton that identifies it as hydrogen.

Isotopes

Isotopes are forms of the same element that have the same number of protons but different numbers of neutrons. This variation does not change the chemical properties of the element significantly, but it can affect its physical properties, such as stability or radioactive behavior. The term 'isotope' comes from the Greek for "equal place," reflecting that isotopes occupy the same position on the periodic table. For hydrogen, its isotopes include protium, deuterium, and tritium:

• Protium: The most common isotope, with 1 proton and no neutrons.
• Deuterium: Also known as "heavy hydrogen," has 1 proton and 1 neutron.
• Tritium: A radioactive isotope with 1 proton and 2 neutrons.

The study of isotopes is critical in various scientific fields, such as medicine, where they are used in diagnostic imaging, and in archaeology, where they help date artifacts.