The Emptiness of Matter
Most objects with which we are familiar are really empty space. The atoms and molecules that make up the everyday objects that we see, such as bricks, wood, glass, and so forth, are largely empty space, even though the objects themselves seem so durable and solid.
An atom consists of a very dense central core that is called the nucleus and a cloud of electrons that surround the nucleus. Depending upon the type of atom being considered, the electron cloud has a radius about 10,000 times as great as the nucleus. If the nucleus were the size of a Ping-Pong ball, the electron cloud would extend over two tenths of a mile in diameter. Most of this distance would be emptiness.
The nucleus, even though it is a very small part of the atom in size, makes up most of the weight of the atom. The fact that most of the empty space comprising objects is due to the electronic cloud is what makes them as light as they are. If you had a cup full of nuclei stripped of their electron clouds so that the nuclei could be tightly packed into the cup, that cup of nuclear matter would weigh about 50,000,000,000 tons.