RETURNING TO NORMAL

If we look at the C-14 atom one more time we can see that C-14 does not last forever. There is a point where it loses those extra neutrons and becomes C-12. That loss of the neutrons is called radioactive decay. That decay happens regularly like a clock. For carbon, the decay happens in a couple of thousand years. Some elements take longer and others have a decay that happens over a period of minutes.

Neutron

NEITHER HERE NOR THERE

Neutrons are the particles on an atom that have a neutral charge. They aren't positive like protons. They aren't negative like electrons. But don't start thinking that they aren't important. Every piece of an atom has huge importance to the way the atom acts and behaves. Neutrons are no exception.

So if an atom has equal numbers of electrons and protons, the charges cancel each other out and the atom has a neutral charge. You could add a thousand neutrons into the mix and the charge will not change. However, if you add a thousand neutrons you will be creating one super-radioactive atom. Neutrons play a major role in the mass and radioactive properties of atoms. You may have just read about isotopes. Isotopes are created when you change the normal number of neutrons in an atom.

You know that neutrons are found in the nucleus of an atom. During radioactive decay, they may be knocked out of there. But under normal conditions, protons and neutrons stick together in the nucleus. Their numbers are able to change the mass of atoms because they weigh about as much as a proton and electron together.

ONE SPECIAL ELEMENT

Did we say that all atoms have neutrons? Ooops. All elements have atoms with neutrons except for one. A normal hydrogen (H) atom does not have any neutrons in its tiny nucleus. That tiny little atom (the tiniest of all) has only one electron and one proton. You can take away the electron and make an ion, but you can't take away any neutrons. That special structure becomes very important when you learn how hydrogen interacts with other elements in the periodic table.

Bonding

BONDING BASICS

You must first learn why atoms bond together. We use a concept called "Happy Atoms." We figure most atoms want to be happy, just like you. The idea behind Happy Atoms is that atomic shells like to be full. That's it. If you are an atom and you have a shell, you want your shell to be full. Some atoms have too many electrons (one or two extra). These atoms like to give up their electrons. Some atoms are really close to having a full shell. Those atoms go around looking for other atoms who want to give up an electron.

Let's take a look at some examples.

We should start with the atoms with atomic numbers between 1 and 18. There is a 2-8-8 rule for these elements. The first shell is filled with 2 electrons, the second is filled with 8 electrons, and the third is filled with 8. You can see that sodium (Na) and magnesium (Mg) have a couple of extra electrons. They, like all atoms, want to be happy. They have two possibilities. (1) They can try to get eight electrons to fill up their third shell. Or (2) they give up a few electrons and have a filled second shell. For them it's easier to give up a few electrons.

What a coincidence! Many other atoms are interested in gaining a few extra electrons.

Oxygen (O) and fluorine (F) are two good examples. Each of those elements is looking for a couple of electrons to make a filled shell. They have one filled shell with two electrons but their second shell wants to have eight. There are a couple of ways they can get the electrons. (1) They can share electrons, making a covalent bond. Or (2) they can just borrow them, and make an ionic bond (also called electrovalent bond).

So we've got a sodium (Na) atom that has an extra electron. We've also got a fluorine (F) atom that is looking for one.

They wind up working together and both wind up happy! Sodium (Na) gives up its extra electron. The sodium (Na) has a full second shell and the fluorine (F) has a full second shell. Two happy atoms! That's one way things are able to bond together. They can give up or share electrons. The two elements have created an electrovalent bond.

Compounds

COMPOUND BASICS

Compounds are groups of two or more elements that are bonded together. There are two main types of bonds that hold those atoms together, covalent and electrovalent/ionic bonds. Covalent compounds happen when the atoms share the electrons, and ionic compounds happen when electrons are donated from one atom to another.

We talked about compounds and molecules in the matter tutorials. When we discuss phase changes to matter, physical forces create the changes. When we talk about compounds, bonds are built and broken down by chemical forces. Physical forces (unless you're inside of the Sun or something extreme) cannot break down compounds. Chemical forces are forces caused by other compounds or molecules that act on substances.

There are millions of different compounds around you. Chances are everything you can see is one type of compound or another. When elements join and become compounds, they lose their individual traits. Sodium alone is very reactive. But when sodium and chlorine combine, they form a non-reactive substance called sodium chloride (Salt, NaCl). The compound has none of the traits or the original elements. The new compound is not as reactive as the original elements. It has a new life of its own.

Date: 2016-01-03; view: 933