4 is correct. Since gases are made of rapidly moving molecules with a relatively high amount of kinetic energy, the molecules have a hard time coming together to form a liquid. You must lower their kinetic energy with a low temperature and force the molecules together with high pressure.
Physical Change because a new substance was not created and if it was a chemical change, a new substance would have to be created.
The first one is exothermic because energy is a reactant, the second formula is endothermic
Answer:
phosphorus - least similar to barium
beryllium - most similar to barium
Explanation:
The formula of the chloride formed between barium and chlorine is BaCl2.
Barium is a metallic element and has the valency of +2. Beryllium is also a group two metal with a valency of +2. Hence the compound formed between beryllium and chlorine is BeCl2
Phosphorus is a nonmetal and forms a completely different chloride from BaCl2. The chloride of phosphorus is PCl5 and PCl3. These are least similar to BaCl2
