Which is the most electronegative atom amongst the following?

Which of the following noble gases do not occur in the elemental state in the atmosphere?

Which of the following does not react with hydrochloric acid to give chlorine as a product?

Red phosphorus is kept under water to protect it from air.

What is the oxidation state of phosphorus in hypophosphoric acid?

What is the catalyst used in contact process in the conversion of Sulphur dioxide to Sulphur trioxide?

Before the invention of CFCs, which of the compounds was used extensively as a refrigerant?

What is the atomicity of halogens?