Which substance can not be decomposed by a chemical change? A. Ne B. N2O C. HF D. H2O
The correct answer and explanation is:
Correct Answer: A. Ne
Neon (Ne) is a noble gas and is considered an element. It cannot be decomposed by a chemical change because it exists as a single atom and not as a compound made of different elements. Chemical decomposition only applies to compounds, which are substances formed by the chemical combination of two or more elements.
Chemical decomposition involves breaking down a compound into its simpler components, either into individual elements or smaller compounds. This can occur through various chemical reactions such as electrolysis, heat decomposition, or reaction with another substance. For example, water (H₂O) can be decomposed by electrolysis into hydrogen and oxygen gases. Similarly, nitrous oxide (N₂O) and hydrogen fluoride (HF) are compounds and can also undergo decomposition reactions under appropriate conditions.
On the other hand, neon is an inert, monoatomic gas that belongs to Group 18 of the periodic table, also known as the noble gases. These gases are known for their chemical stability and very low reactivity due to their full valence electron shells. This full outer shell makes neon extremely stable and unlikely to form bonds or participate in chemical reactions under normal conditions.
Because neon is already in its most stable elemental form and not bonded to any other element, there is no chemical process that can break it down into simpler substances. It exists as a pure element and thus cannot be chemically decomposed. In contrast, all the other choices—N₂O, HF, and H₂O—are compounds and therefore can be broken down by chemical means.
In conclusion, among the listed substances, only Ne (neon) cannot be decomposed by a chemical change because it is a single, stable element rather than a compound.