C is the answer I’m pretty sure
Answer:
Ni
Explanation:
An active metal is a highly reactive metal. Active metals are found high up in the activity series.
Active metals react with other metals that are lower than them in the activity thereby displacing the lower metals from a solution of their salts. This is what may have happened in the other two reactions.
Ni is the most active metal listed in the question since it can react a compounds with Pb(NO3)2(aq) to liberate Pb metal.
A mile.
For reference, it's about 1,607 or so meters, and 1km is 1,000.
So, to determine the number of neutrons in atom, we only have to subtract the number of protons from the mass number. Take note that the nucleus of an atom is composed of protons and neutrons. And the number of particles present in the nucleus is referred as mass number (Also, called as atomic mass).
