Question

Which element has only one proton? a. hydrogen b. an isotope c. helium d. a free radical

Short answer

Hydrogen has only one proton.

Step-by-step solution

Understanding the Question

We need to identify the element that has exactly one proton. The number of protons identifies the element in the periodic table.

Review Option A: Hydrogen

Hydrogen is the first element on the periodic table, and it is known to have exactly one proton, making it the simplest and the lightest element.

Evaluate Option B: Isotope

An isotope refers to different forms of the same element with varying numbers of neutrons. It does not specifically refer to an element with one proton.

Assess Option C: Helium

Helium is the second element on the periodic table and has two protons in its nucleus, so it cannot be the correct answer.

Consider Option D: Free Radical

A free radical is a molecule or atom with an unpaired electron; it is a chemical property rather than a characteristic related to the number of protons in an element.

Select the Correct Option

Based on the analysis, the only element that has exactly one proton is hydrogen.

Key concepts

Protons

Protons are fundamental particles found within every atom's nucleus. They carry a positive electrical charge and have a relative mass of 1 atomic mass unit (amu). The number of protons in an atom's nucleus is crucial as it defines the identity of the element. For instance, an atom with only one proton is hydrogen, which is the simplest and lightest element in the universe.

Protons play a significant role in binding the nucleus together with neutrons through nuclear forces, which are among the strongest forces in nature. Despite protons having like charges, which typically repel due to electromagnetism, the nuclear force keeps them bound tightly within the nucleus. Understanding protons is essential for comprehending the atomic structure.

Elements

Elements are pure substances consisting entirely of one type of atom. They are characterized by the number of protons in their nuclei. This number, known as the atomic number, determines the chemical nature and properties of the element. For example, the element hydrogen has an atomic number of 1 because it has one proton in its nucleus.

All known elements are organized in the periodic table, where each element is given a unique position based on its atomic number. Interestingly, while some elements like helium are noble gases and inert, others like fluorine are highly reactive. Each element's position within the periodic table reveals a lot about its chemical properties and relationships with other elements.

Periodic Table

The periodic table is a scientific chart displaying all known chemical elements. It is arranged in order of increasing atomic number, from left to right and top to bottom. Elements in the same column, known as groups, have similar chemical properties and the same number of valence electrons.

The table is divided into metals, non-metals, and metalloids. Metals are typically on the left and center, non-metals on the right, and metalloids lie between them. This arrangement helps predict characteristics and reactions of the elements based on their position.

• Columns are called groups and include elements with similar properties.
• Rows are called periods and represent energy levels of electrons.
Understanding the periodic table is key to studying elements and their interactions within chemical reactions.

Isotopes

Isotopes are variants of the same chemical element that have the same number of protons but different numbers of neutrons. This difference in neutron count results in isotopes of the same element having different atomic masses. For instance, carbon has two stable isotopes: carbon-12 and carbon-13, with 6 and 7 neutrons, respectively.

Isotopes can be stable or radioactive. Radioactive isotopes, or radioisotopes, decay over time and emit radiation. They have important applications in industry, medicine, and archaeology, such as in radiocarbon dating.

• Stable isotopes do not change or decay.
• Radioactive isotopes are used in medical imaging and treatment, such as cancer therapy.

The concept of isotopes is fundamental in understanding the diversity among elements and their behavior in different environments.