Which subatomic particle correctly determines an atom's identity and chemical properties?

• A. Number of protons
• B. Number of electrons in the nucleus
• C. Number of neutrons
• D. Atomic mass

Answer: (A)

Verified step by step guidance

1. Understand that an atom's identity is defined by the element it represents, which is determined by the number of protons in its nucleus. This number is called the atomic number.
2. Recognize that the number of protons uniquely identifies an element because no two different elements have the same number of protons.
3. Know that the chemical properties of an atom are largely influenced by the arrangement and number of electrons, which are equal to the number of protons in a neutral atom, but the identity itself depends on protons.
4. Note that neutrons contribute to the atomic mass and isotopes of an element but do not change the element's identity or its basic chemical properties.
5. Atomic mass is the sum of protons and neutrons and does not determine the element's identity; it varies among isotopes of the same element.