Which of the following elements are stable as atoms? Kr Rn Be F Submit Previous Answers Request Answer
The Correct Answer and Explanation is:
Among the elements listed — Kr (Krypton), Rn (Radon), Be (Beryllium), and F (Fluorine) — the ones that are stable as atoms are:
- Kr (Krypton): Krypton is a noble gas, meaning it is chemically inert and stable. Noble gases have complete electron shells, which makes them unlikely to form bonds with other elements. This stability allows krypton to exist naturally as a single, unreactive atom.
- Be (Beryllium): Beryllium is a stable atom, but it is reactive. It is a Group 2 alkaline earth metal with two valence electrons. These two electrons are readily lost to form a +2 ion, which is why beryllium is typically found in compounds rather than as a free element. However, as an atom, beryllium is stable, just reactive in nature.
- F (Fluorine): Fluorine is a halogen, highly reactive due to its seven valence electrons. It tends to form bonds by accepting one electron to complete its outer shell. Although fluorine atoms are stable in their own right, they rarely exist in isolation because they are so reactive and seek to form bonds with other elements, particularly metals.
- Rn (Radon): Radon is a noble gas but is unstable due to its radioactive properties. While it can exist as a neutral atom, radon is radioactive, which means it undergoes spontaneous decay, emitting radiation over time. Therefore, radon is not stable in the long term and is a health hazard because of its radioactivity.
Summary:
- Stable as atoms: Kr (Krypton), Be (Beryllium)
- Unstable: Rn (Radon) due to radioactivity, F (Fluorine) due to its high reactivity
