Which is a chemical property of oxygen? 1.It reacts with iron to form rust.
2.It is a gas at room temperature.
3.It expands when heated.
4.It combines to form O 2 molecules.

I think the answer is 1

i just learned this about two weeks ago

Explanation:

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

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante