Question

Which element behaves chemically both as a metal and as a non-metal (a metalloid)?

• A. Boron
• B. Argon
• C. Carbon
• D. Xenon

Hint:

This element sits along the "staircase" line separating metals from non-metals.

Answer 1

The Correct Option is A

We must pick the element that shows dual, metal-like and non-metal-like, chemical behaviour.

1. Argon is a noble gas with a complete outer shell, it barely reacts with anything, so it shows neither strong metallic nor non-metallic chemical behaviour.
2. Xenon is also a noble gas, forming only a few compounds under special conditions, it is not classed as a metalloid.
3. Carbon is firmly a non-metal, forming acidic oxides and covalent bonds typical of non-metals only.
4. Boron forms an acidic oxide like a non-metal but has a partly metallic lustre and network covalent structure, placing it right on the metal to non-metal borderline, which is the definition of a metalloid.

So boron, option A, is the element that behaves both as a metal and a non-metal.