Answer:
An atom is a complex arrangement of negatively charged electrons arranged in defined shells about a positively charged nucleus. This nucleus contains most of the atom's mass and is composed of protons and neutrons (except for common hydrogen which has only one proton).
Explanation:
Besides building teeth and bones, calcium also keeps your blood and muscles moving and helps your nerves send messages from your brain to the rest of your body. Your body can't make calcium, so you need to get it from food or supplements. While you're pregnant, try to get at least 1,000 mg of calcium every day.
I think you divide something
2 BN(s) + 3 Cl2(g) = 2 BCl3(g) + N2(g)
Around 350 BC, the great Aristotle declared that the Earth was a sphere (based on observations he made about which constellations you could see in the sky as you travelled further and further away from the equator) and during the next hundred years or so, Aristarchus and Eratosthenes actually measured the size of the Earth!
