There are 18 Elements in the fifth period.
It’s mass number would be 5 as it’s the protons and the neutrons added together
Protons, neutrons, and electrons.
All organisms need water, vitamins, minerals, and salt together to balance things out.
Answer:
You may be referring to the gas that makes up 21% of the earth's atmosphere, which is oxygen.
Explanation:
According to NASA, the gases in Earth's atmosphere include:
Nitrogen — 78 percent
Oxygen — 21 percent
Argon — 0.93 percent
Carbon dioxide — 0.04 percent
(Trace amounts of neon, helium, methane, krypton and hydrogen, as well as water vapor)
