Which one of the following does not occur as diatomic molecules in elemental form?
A) oxygen
B) nitrogen
C) sulfur
D) hydrogen
E) bromine
The correct answer and explanation is :
Correct Answer: C) Sulfur
Explanation:
In chemistry, diatomic molecules are molecules composed of only two atoms, which can either be of the same or different chemical elements. However, when we refer to diatomic elements, we specifically mean elements that exist in nature as diatomic molecules in their elemental form — that is, two atoms of the same element bonded together. These elements are considered molecular elements rather than atomic ones in their natural state.
The seven elements that exist as diatomic molecules under standard conditions (room temperature and pressure) are often remembered using the mnemonic “Have No Fear Of Ice Cold Beer”, which stands for:
- H – Hydrogen (H₂)
- N – Nitrogen (N₂)
- F – Fluorine (F₂)
- O – Oxygen (O₂)
- I – Iodine (I₂)
- Cl – Chlorine (Cl₂)
- Br – Bromine (Br₂)
Looking at the options:
- A) Oxygen – Exists naturally as O₂, a diatomic gas. ✅
- B) Nitrogen – Exists as N₂, a very stable diatomic gas. ✅
- C) Sulfur – Exists primarily as S₈, an octatomic molecule in solid form, not diatomic. ❌
- D) Hydrogen – Naturally found as H₂, a diatomic gas. ✅
- E) Bromine – Exists as Br₂, a diatomic liquid at room temperature. ✅
Thus, sulfur (S) is the only element listed that does not form diatomic molecules in its elemental form. Instead, sulfur typically forms cyclic octatomic molecules (S₈), which are ring-shaped and stable in the solid state.
In summary, sulfur is unique among the choices given because it is not diatomic in its elemental form. Understanding which elements form diatomic molecules is fundamental in chemistry, especially when writing and balancing chemical equations.