The molecules of which of the following substances contain the same kind of…
2011
The molecules of which of the following substances contain the same kind of atoms?
Answer: A. Oxygen — A pure substance is classified, in its molecular form, as an element when every atom in its molecule is of the same kind; it is classified as a compound when…
- A.
Oxygen
- B.
Water
- C.
Carbon dioxide
- D.
Sulphur dioxide
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Correct answer: A
A pure substance is classified, in its molecular form, as an element when every atom in its molecule is of the same kind; it is classified as a compound when its molecules contain atoms of two or more different elements bonded together.
Oxygen is O2, so every atom in its molecule is an oxygen atom — the same kind throughout.
Water is H2O, combining hydrogen atoms with an oxygen atom, so two different kinds of atoms are present.
Carbon dioxide is CO2, one carbon atom bonded to two oxygen atoms — again two different kinds.
Sulphur dioxide is SO2, one sulphur atom bonded to two oxygen atoms — again two different kinds.
Only the formula for oxygen repeats a single element symbol; the other three formulas each combine two distinct element symbols, confirming oxygen is the only substance listed whose molecules contain the same kind of atom throughout.