(D) What are ELECTRONS, PROTONS, and NEUTRONS? A picture works best and this is basically an atom. There are three pieces to an atom. There are electrons, protons, and neutrons. That's all you have to remember. Three things!

As you know, there are many elements in the PERIODIC TABLE. Over 100! Well the thing that makes those elements different, is the number of electrons, protons, and neutrons. Take a look at the picture, the protons and neutrons are in the center of the atom. Scientists call the center the NUCLEUS. The electrons are always found whizzing around the center, like the earth orbiting the sun.

You can also see that each piece has either a "+", "-", or a "0". That refers to its CHARGE. You know when you get a shock from a socket, static electricity, or lightning? Well those are all different types of charges. Even in something as small as an atom, there are charges.

The electron always has a "-" or negative charge. The proton always has a "+" or positive charge. If the charge of an entire atom is "0", that means there are equal number of positive and negative pieces. Equal numbers of electrons and protons. The third particle is the neutron. It has a neutral charge (a charge of zero).

ORBITAL BASICS

(1) A shell is sometimes called an orbital or energy level.
(2) Shells are areas that surround the center of an atom.
(3) The center of the atom is called the nucleus.
(4) Electrons live in something called shells.

ELECTRONS SPIN IN SHELLS
As you know, ELECTRONS are always moving, spinning very quickly around the NUCLEUS. As the electrons spin they can move in any direction, as long as they stay in their shell. Any direction you can imagine; upwards, downwards, sidewards, electrons can do it. The shell is the distance from the nucleus that the electron spins. If you are an electron in the first shell, you are always closer to the nucleus than the electrons in the second shell.
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SHELLS HAVE NAMES
Scientists use letters to name the orbitals around a nucleus. They use the letters "k,l,m,n,o,p, and q". The "k" shell is the one closest to the nucleus and "q" is the furthest away. We are only learning about ELEMENTS 1-18 and they only use shells "k", "l", and "m".
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SHELLS ONLY HOLD SOME ELECTRONS
Not all shells hold the same number of electrons. For the first 18 elements, there are some rules. The k-shell only holds two electrons. The l-shell only holds eight electrons. The m-shell only holds eight electrons for the first 18 elements. The m-shell can actually hold up to 18 electrons as you move up the periodic table.

YOU CAN'T KNOW WHERE AN ELECTRON IS
Even though we're telling you that electrons are in specific shells, or moving in specific directions, we can't tell you exactly where an electron is. We can only approximate, or guess, where that electron is. According to something called QUANTUM THEORY, an electron can be found anywhere around the nucleus. But using advanced math, scientists are able to approximate, or guess, that electrons are in general areas. These areas are the shells.

THE GREAT NIELS BOHR
Now it's time to give some credit. You know all this stuff we're learning about. These orbitals, shells, spinning electrons, and other stuff were all thought of by one guy.

Niels Bohr came up with all these ideas in 1913. He did a lot of research and came up with these ideas. So when you get confused, you should imagine how Dr. Bohr felt. He didn't have anyone he could ask questions.

We're not positive that Niels had green hair, but you never know.