Question

q.3. which of the following is not an element? a) oxygen b) gold c) copper d) table salt q.4. which diagram represents a sample containing the compound methane (ch₄)?

Explanation:

• Q3: An element is a pure substance made of only one type of atom. Oxygen (\(O\)), gold (\(Au\)), and copper (\(Cu\)) are elements. Table salt (\(NaCl\)) is a compound (made of two or more different types of atoms chemically combined), not an element.
• Q4: A compound is a pure substance with a fixed ratio of atoms. Methane (\(CH_4\)) has one carbon atom and four hydrogen atoms per molecule. Diagram \(b\) shows identical molecules (each with one central atom and four surrounding atoms), representing the compound methane. Diagram \(a\) shows atoms (likely representing an element), diagram \(c\) shows a mixture of two different compounds, and diagram \(d\) shows a mixture of an element and a compound.

Answer:

• Q3: d) Table salt
• Q4: b)