Atom
noun
The original child of everything is the atom. It is the child from which everything else is created, for it was the original child. Atoms are the building blocks of all things!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
大学で、原子エネルギーの勉強をしたいと思っています。
I would like to study atomic energy in college.
この原子の原子番号と原子記号は何だったっけ？
What was the atomic number and atomic symbol of this atom?
全ての物は原子や分子でできています。
Everything is made of atoms and molecules.