It refers to the combining capacity of an atom but it specifies its charge.
A. oxidation number
B. valence electron
C. Avogadro’s number
D. molecular weight
The correct answer and explanation is :
The correct answer is A. oxidation number.
Explanation:
The oxidation number (or oxidation state) refers to the charge an atom would have if all the bonds it forms were considered completely ionic. It is a measure of the combining capacity of an atom, taking into account the number of electrons that an atom can donate or accept during a chemical reaction. This concept is critical in understanding how atoms bond in molecules and how they interact in chemical reactions, especially redox (reduction-oxidation) reactions.
Oxidation Number:
The oxidation number of an atom is an integer that represents its charge in a molecule or compound. It helps chemists understand how electrons are transferred during chemical reactions. For example:
- In water (H₂O), oxygen has an oxidation number of -2 (since it is more electronegative), and hydrogen has an oxidation number of +1.
- In sodium chloride (NaCl), sodium has an oxidation number of +1, and chlorine has an oxidation number of -1.
Why Not the Other Options?
- B. Valence Electrons: Valence electrons are the electrons in the outermost shell of an atom. They determine how an atom bonds with others, but they don’t specify the charge of the atom in a molecule. While valence electrons play a role in determining the oxidation state, they are not the same as the oxidation number, which explicitly refers to the charge of an atom in a compound.
- C. Avogadro’s Number: Avogadro’s number (approximately 6.022 × 10²³) represents the number of molecules, atoms, or particles in one mole of a substance. It does not relate to an atom’s charge or its combining capacity.
- D. Molecular Weight: Molecular weight (or molecular mass) is the mass of a molecule, calculated as the sum of the atomic masses of the atoms in the molecule. This does not tell us anything about the charge or the combining capacity of atoms in the molecule.
Thus, oxidation number is the term that best fits the description of “combining capacity of an atom but specifying its charge.”