Please help! Which Of the following observations of Zinc metal are physical properties?
1. Zinc reacts with hydrochloric acid, forming hydrogen gas.
2. Zinc melts at 782°C.
3. The density of Zinc is 7.14 g/cm3.
4. Zinc is a moderately good electrical conductor.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

a:

by the combination of an unlimited number of elements

the answer is 0.42 is that is an option. this question provides no info