The answer is Strontium(Sr). The reactive increase from right to left. And this element has two valence electrons. So Rb is not correct. Then the very reactive metal is Sr.
Its d its the only one that makes sense
Answer:
PCl₅ because a subscript indicates 5 chlorine atoms.
Explanation:
As the name suggests, phosphorous pentachloride contains 5 chlorine atoms as penta means five and phosphorous means P atoms.
Explanation:
A system can be either closed or open; A closed system is a system that is completely isolated from its environment. An open system is a system that has flows of information, energy, and/or matter between the system and its environment, and which adapts to the exchange.