Use carbon-12, the most common isotope of carbon, to define these terms: atomic number, mass number, valence. Which of these numbers is most related to the chemical behavior of an atom? Explain.

Verified step by step guidance

1. Define the atomic number: The atomic number is the number of protons in the nucleus of an atom. For carbon-12, this number is 6 because carbon has 6 protons. This is what identifies the element as carbon.
2. Define the mass number: The mass number is the total number of protons and neutrons in the nucleus of an atom. For carbon-12, the mass number is 12 because it has 6 protons and 6 neutrons. Use the formula: $\mathrm{Mass} \mathrm{Number}=\mathrm{Protons}+\mathrm{Neutrons}$.
3. Define valence: Valence refers to the number of electrons in the outermost shell of an atom that are available for bonding. For carbon, the atomic number is 6, meaning it has 6 electrons. These are distributed as 2 in the first shell and 4 in the second shell, so the valence of carbon is 4.
4. Explain which number is most related to chemical behavior: The valence is most related to the chemical behavior of an atom because it determines how an atom interacts with other atoms to form chemical bonds. For example, carbon's valence of 4 allows it to form up to 4 covalent bonds with other atoms.
5. Summarize the relationships: The atomic number identifies the element, the mass number provides information about the atom's nucleus, and the valence determines the atom's chemical reactivity and bonding potential.

Key Concepts

Atomic Number

The atomic number of an element is the number of protons found in the nucleus of its atoms. For carbon-12, the atomic number is 6, indicating that it has six protons. This number uniquely identifies the element and determines its position in the periodic table, influencing its chemical properties and behavior.

Mass Number

The mass number is the total number of protons and neutrons in an atom's nucleus. For carbon-12, the mass number is 12, as it has 6 protons and 6 neutrons. While the mass number provides information about the atom's isotopes, it does not directly influence the chemical behavior of the atom.

Valence

Valence refers to the ability of an atom to bond with other atoms, determined by the number of electrons in its outermost shell. For carbon, which has four valence electrons, this allows it to form four covalent bonds with other elements. Valence is crucial for understanding an atom's chemical behavior, as it dictates how atoms interact and combine to form molecules.