Atoms

• Atomicity of Oxygen in Ozone (O₃) - The atomicity refers to the number of atoms of the element present in one molecule of a compound. In the case of ozone (O₃), the molecule consists of three oxygen atoms, so the atomicity of oxygen in ozone is 3.

Explanation:

The molecule of ozone (O₃) consists of three oxygen atoms bonded together. Therefore, the atomicity of oxygen in ozone is 3, as there are three oxygen atoms in one molecule of ozone.

• Option 1: 2 - This is incorrect. Phosphorus does not exist as a diatomic molecule under normal conditions, so its atomicity is not 2.
• Option 2: 3 - This is incorrect. Phosphorus typically does not form a molecule with three atoms in its stable allotropes.
• Option 3: 4 - This is the correct answer. Phosphorus exists as P₄ molecules in its most stable allotrope (white phosphorus), which means its atomicity is 4. The atomicity of an element is the number of atoms in one molecule of that element.
• Option 4: 5 - This is incorrect. Phosphorus does not form molecules with five atoms in its most stable form. The atomicity of phosphorus is 4.

Explanation:

Phosphorus, in its most stable allotrope, exists as a P₄ molecule, meaning it consists of four phosphorus atoms. Therefore, the atomicity of phosphorus is 4. The molecular structure of phosphorus involves a tetrahedral arrangement of phosphorus atoms in the P₄ molecule, which is the form most commonly encountered in nature.

• Option 1: Mass/molecular mass - This is incorrect. Atomicity is not directly calculated by dividing the mass of an element by its molecular mass.
• Option 2: Mass of the element - This is incorrect. The atomicity is not calculated based on the mass of the element alone. Atomicity refers to the number of atoms in one molecule of the element, not its mass.
• Option 3: Molecular mass X atomic mass - This is incorrect. Atomicity is not calculated by multiplying molecular mass and atomic mass. The calculation involves dividing molecular mass by atomic mass.
• Option 4: Molecular mass / atomic mass - This is the correct answer. Atomicity is calculated by dividing the molecular mass of a compound by the atomic mass of its constituent element. This gives the number of atoms in one molecule of the element.

Explanation:

Atomicity refers to the number of atoms in one molecule of an element. It is calculated using the formula:

Atomicity = Molecular mass / Atomic mass

For example, in the case of oxygen (O₂), the molecular mass is approximately 32 g/mol, and the atomic mass of oxygen is approximately 16 g/mol. Therefore, the atomicity of oxygen is:

Atomicity = 32 / 16 = 2

This shows that one molecule of oxygen contains two oxygen atoms, so the atomicity of oxygen is 2.

• Option 1: Valency of an element - This is incorrect. The valency of an element refers to its ability to combine with other elements, typically based on the number of electrons in its outer shell. Atomicity is a different concept, relating to the number of atoms in a molecule of an element.
• Option 2: Atomic mass - This is incorrect. The atomic mass refers to the mass of an atom, usually measured in atomic mass units (amu). Atomicity, on the other hand, refers to the number of atoms in one molecule of an element, not its mass.
• Option 3: Number of atoms in one molecule of an element - This is the correct answer. The atomicity of an element refers to the number of atoms that make up a single molecule of that element. For example, the atomicity of oxygen (O₂) is 2, as it consists of two oxygen atoms per molecule.
• Option 4: Isotope of an element - This is incorrect. An isotope refers to different forms of the same element that have the same number of protons but different numbers of neutrons. It is unrelated to the concept of atomicity, which deals with the number of atoms in a molecule.

Explanation:

The atomicity of an element refers to the number of atoms that make up a single molecule of that element. For example, oxygen (O₂) has an atomicity of 2 because each molecule of oxygen consists of two oxygen atoms. The atomicity helps define the molecular structure of elements, whether they exist as diatomic molecules (like O₂), tetraatomic molecules (like phosphorus, P₄), or monatomic molecules (like noble gases such as neon, Ne).

• Atomicity of Primary Gases - Primary gases like oxygen (O₂), nitrogen (N₂), hydrogen (H₂), and others consist of molecules that are made up of two or more atoms of the same element. The atomicity of these primary gases depends on the type of molecule they form.
• For example:
  • Oxygen (O₂): The atomicity of oxygen in O₂ is 2 because it consists of two oxygen atoms.
  • Nitrogen (N₂): The atomicity of nitrogen in N₂ is 2 because it consists of two nitrogen atoms.
  • Hydrogen (H₂): The atomicity of hydrogen in H₂ is 2 because it consists of two hydrogen atoms.
  • Ozone (O₃): The atomicity of oxygen in ozone is 3 because it consists of three oxygen atoms.

Explanation:

The atomicity of primary gases depends on how many atoms of the element are present in a molecule of that gas. For example, oxygen (O₂) has an atomicity of 2 because it consists of two oxygen atoms, nitrogen (N₂) has an atomicity of 2, hydrogen (H₂) has an atomicity of 2, and ozone (O₃) has an atomicity of 3 because it consists of three oxygen atoms.

• Option 1: Divisible - This is incorrect. The term "atomos" actually refers to something that cannot be divided, not something that can be divided.
• Option 2: Indivisible - This is the correct answer. The Greek term "atomos" means "indivisible," referring to the belief that matter is made up of small, indivisible particles, which is the origin of the word "atom."
• Option 3: Macro molecule - This is incorrect. "Macro molecule" refers to large molecules, such as proteins or DNA, and is unrelated to the Greek term "atomos."
• Option 4: Soft sphere - This is not correct. The term "atomos" does not refer to a "soft sphere" but to an indivisible particle.

Explanation:

The term “atomos” comes from Greek, meaning “indivisible.” Ancient Greek philosophers believed that matter could be divided only up to a certain point, and beyond that, the particle would be indivisible. This concept later evolved into our modern understanding of atoms in chemistry.