Q. Which of the following pairs of elements and their valencies are correctly matched?

1. Neon - zero
2. Nitrogen - five
3. Phosphorus - three point five
4. Potassium - one

Select the correct option using the codes given below:
Answer: Only 1, 3 & 4
Notes: Neon has a valency of zero, being a noble gas. Nitrogen has a valency of 3, not 5. Phosphorus commonly shows an average valency of 3.5, due to its variable oxidation states. Potassium has a valency of 1. Hence, only options 1, 3, and 4 are correctly matched.