1. Introduction to Chemistry
Part One

2. Any substance that contains only one kind of an atom is known as an element.
For example, Hydrogen, the simplest and most abundant element in the universe is made entirely of Hydrogen atoms.
We call it “simple” because it’s atoms contain only one proton and electron. Because of this construction, it is also the “lightest” element.
A more complex element like Gold has many more sub- atomic particles. For this reason, it has different characteristics and is ultimately heavier than an element like hydrogen.
Yet in every case, elements cannot be broken down in into simpler substances. Even if you reduce a sample of a particular element to the point of a single tiny atom, the atom itself will still be uniquely “hydrogen” or “gold”.
What sort of atoms would make up the element Neon?
NEON ATOMS!

3. Something very complex - like the human body - can certainly be broken down into it’s simple ingredients – elements. But whenever we reach this level in the deconstruction of anything in the universe - the point of elements - we can go no further! This is why elements are so important, and why the understanding of them is vital in all scientific fields.
INTERESTING FACT:
When the universe began almost 14 billion years ago, there was only hydrogen. All of the other more complex elements where formed inside of stars throughout the years by Nuclear Fusion. When stars die, they scatter this material throughout the universe to make other stars and eventually planets. You, and everything else that exists are star stuff !

4. Elements are made up of Atoms, the smallest particle that has any of the properties of the element. John Dalton, in 1803, proposed a modern theory of the atom based on the following assumptions:
1. Matter is made up of atoms that are indivisible and indestructible.
2. All atoms of an element are identical.
3. Atoms of different elements have different weights and different chemical properties.
4. Atoms of different elements combine in simple whole numbers to form compounds.
5. Atoms cannot be created or destroyed. When a compound decomposes, the atoms are recovered unchanged.
The Law of Conservation of Matter states that matter is never created or destroyed in a closed system. It is only “rearranged”. For example, when you burn a piece of paper, matter might seem to disappear, but the elements that made of that piece of paper are only separating and going elsewhere – some into the air, some remaining as ash. Eventually all of these atoms will go into making other things. This may even be viewed as a simpler demonstration of a supernova in a way! The Laws of Conservation of Mass / Energy are really one in the same.

5. Each element is represented by a unique symbol
Each element is represented by a unique symbol. The notation for each element can be found on the Periodic Table of Elements. .
The “invention” of this table is generally credited to Russian chemist Dmitri Mendeleev in Mendeleev intended the table to illustrate recurring ("periodic") trends in the properties of the elements. This table has been (and continues to be) constructed based on new discoveries and understandings of elements. It is relied upon in virtually every branch of science.
Currently, 117 elements appear on the Periodic Table. Each holds a specific place on the table according to it’s unique characteristics.
**Absolutely everything that exists in the universe is made up of what appears on this table!

6. CAN YOU ANSWER THESE QUESTIONS?
Each block in the Periodic Table contains the same information about each element.
CAN YOU ANSWER THESE QUESTIONS?
Krypton
What’s the name of this Element?
How many protons does each atom’s nucleus contain?
How many electrons orbit the nucleus?
Are there more protons or neutrons in the nucleus? 36 36
Neutrons
Why does the Atomic Number serve as both the separate number of Protons and Electrons in an atom?
Bonus!

7. The World of the “ I’s ”
Many of the lighter elements (the first few rows of the period table) have a similar number of protons and neutrons in their nucleus. This is why their atomic mass resembles twice their atomic number.
The heavier elements typically have more neutrons than protons however. The sum that is the atomic mass then, is considerably more than twice the atomic number.
The very same element can also appear in states where the number of neutrons varies while the quantity of protons will always remain the same.
This is referred to as an Isotope – a variation in the neutron count within the same element.

8. Isotopes are not to be confused with Ions.
Whereas isotopes deal with Nucleons (particles in an atom’s nucleus) Ions are concerned with the orbiting electrons in an atom.
Atoms are neutral in their natural state – without a charge. This is due to the number of electrons equaling the number of protons. There is a “balance” between negatively charged electrons and positively charge protons. - +
Adding or taking away an electron in an atom creates an Ion – an atom with a charge.
When an atom has an extra electron the atom now has a negative charge (anion). Take away an electron and you would have a positively charged atom (cation).
Cl+
Cl -
Chlorine ions would be expressed like this
Because atoms like to be neutral, they will often share
Fact:
electrons in order to avoid having a charge. Therefore, Ions play a key role in the bonding of atoms and elements.