Elements, Compounds, &
Subatomic Particles

What is the Periodic Table?




It is a table (duh) which shows all of the known elements.
The table is arranged according to atomic number (number of protons) of EACH element.
Incidentally, when arranged according to atomic number, a pattern in the table emerges.
Elements in the same column share a lot of similar properties (or characteristics).



An element is a pure substance which cannot be subdivided, broken down, split up, (etc.) into anything else.
You can cut up, try to break apart, and try to chemically break down iron but you will fail! Iron will never stop being iron.
 Examples of elements: gold, silver, iron.







Are not elements.
In other words, we don’t usually see elements laying around.
We usually see compounds.
Compound: a substance made up of two or more elements which are chemically combined.
Examples: water (H
2
O) is made of two atoms of hydrogen for every one atom of oxygen).
Even the oxygen we breath is not the “element” O, but a compound. It is O
2
, two atoms of oxygen.


 We can’t break the iron, gold, or silver up into new substances. BUT they are made up of smaller particles, called: sub-atomic particles:

 Protons
Neutrons
 Electrons.
Think of it this way: you can’t cut me up into different organisms, but you can “look inside” me and see my organs. Likewise, you can’t cut iron up into different substances, but you can “look inside” and see protons, neutrons, and electrons. Metaphorically, of course…

 Protons are the MOST important subatomic particle?



Why? Because the number of protons makes the element.
For example, Nitrogen has 7 protons. If I take away a proton I wouldn’t have
Nitrogen anymore, I’d have
Carbon!
Protons have a + charge.

 Sadly, for the neutron it is not nearly as important as a proton 
 However, they do carry some importance.




Usually there are the same number of neutrons in an atom as protons.
But! If you add or take away neutrons even though you won’t change the element you will slightly change some of its properties. You will in fact make a…
Isotope: a different version of the element due to having more or less neutrons.
Neutrons have a “neutral” (or no) charge.





Carbon always has 6 protons and so it usually has 6 neutrons. This is called Carbon-12 (6+6=12)
Makes sense because like I already said, an element’s atom usually has the same number of neutrons as protons. But not always…
Carbon does have isotopes out there!! And what’s an isotope?
Carbon-13, Carbon-14
(etc.)



If I had to rank subatomic particles in order of importance, protons would be first, neutrons would be last, and electrons would be in the middle.
Electrons are not as important as protons because you CAN change the number of electrons without changing the element.
Remember the number of protons determines the element!




Electrons have a negative charge.
Look at this picture

Notice how much smaller the electron is… This is true in “real” life. Protons and Neutrons are roughly the same size. Electrons are itty, bitty babies in comparison.







In an electronically neutral atom the number of electrons are the same as protons.
When elements come together to form compounds, electrons may be shared between them equally, not affecting the charge. OR
One atom may be a big bully and hog the shared electron(s) more often than the other atoms. Meanie! This will affect the charge because the little thief has the more negative electrons more frequently.
Remember water, a compound?
The configuration H
2
0 is 100% determined by how Hydrogen’s and
Oxygen’s electrons dance together (or what Chemists call bonding).
Oxygen and hydrogen dance together nicely and share the electrons evenly!
How nice!







Protons are positively charged subatomic particles which
DETERMINE what element we are talking about. An element with 2 protons will always be Helium. An element with 4 protons will always be Beryllium.
How many protons does Selenium have?
How many protons does Technetium have?
What element has 80 protons?
What element has 86 protons?
***Remember the atomic number IS the number of protons, and it will NEVER change for any particular element!****





A proton is positively charged and occupied the nucleus, or the center part of the atom.
Protons share that nucleus, or center of the atom, with neutrons. The number of neutrons is usually the same as the number of protons.
Sometimes the number of neutrons is less or more than the number of protons, we call these versions of the element isotopes.
Isotopes are the same element because they have the same number of protons, BUT they have some slightly different characteristics!






Neutrons have a neutral (or no) charge.
Neutrons are roughly the same size as protons.
Electrons are really, really, really small.
Electrons exist outside of the atom’s nucleus, orbiting around the nucleus like planets orbit the sun.
Electrons are negatively charged.
 Electrons are really important when two elements bind together to form compounds.
 http://www.youtube.com/watch?v=lP57gEWcisY