Science Fast Facts 
Atoms
Did you know that all matter is made of atoms? Everything that you can see, touch, feel is made
of atoms. In fact, everything that exists in the whole universe is made of atoms. All atoms are
made of the same things: protons, neutrons, and electrons.
Protons
Neutrons
Positive charge
Found in nucleus
Same as atomic number
No electrical charge
Found in nucleus
Subtract atomic number
from the atomic mass to
calculate neutrons
Electrons
Negative charge
Found in electron cloud- outside the nucleus
Same as number of protons
Nucleus
Electron Cloud
The atomic number of an atom is the number of protons it has.
This is the whole identity of the atom. The element Hydrogen has one proton. If you could add
a second proton to Hydrogen, it would not be Hydrogen anymore, it would become Helium – a
totally different element.
Some of the electrons are important in determining the chemical properties of an element.
Valence electrons – the electrons found on the outside energy shell of an atom – determine how
reactive an element is with other elements and compounds. Reactivity is a chemical property.
Groups
[
P
e
r
i
o
d
s
[Type a quote
Most Reactive
Less Reactive (Halogens very reactive)
Science Fast Facts 
Each group on the periodic table has similar chemical properties that are related to having the
same number of valence electrons. Group 1 elements all have one valence electron, Group 2
elements all have two valence electrons, and so on. The most reactive elements are on the left
side of the table. The far right side (Group 18 or 8A) is the Noble Gases, they are not very
reactive at all because they have 8 electrons in their outside energy level.
1
Atomic Number
Each element on the periodic table has
H
Element Symbol
abbreviations that are used to represent
Hydrogen
1.007
Element Name
an element symbol. Symbols are
the element. These symbols are used in
chemical formulas. For example: H
stands for Hydrogen and O for Oxygen
Atomic Mass
which form the compound H2O or water.
Chemical Formulas
Everything that exists in the universe is on the
periodic table of the elements. You may notice
there is no element for water. Where does
water come from then? It exists, but is not on
the table. Well, water is on the table. You just
have to know what elements make up water.
2 Hydrogen atoms + 1 Oxygen atom = water molecule
This is written using the chemical formula H2O.
2C6H12O6
Coefficient
Subscript
The subscript tells you how many of
each atom you have. The coefficient
tells you how many total molecules
you have. You multiply the
coefficient by the subscript to find
the total number of atoms.
When different elements from the table combine in different ways, completely new chemical
substances are formed. When elements combine together or break apart from a molecule, a
chemical reaction occurs. How can you tell if you are observing a chemical reaction?
Evidence of a Chemical Change
Energy released – temp increase
Energy absorbed – temp decrease
Gas released – bubbles
Light emitted
Precipitate forms – solid forms
Color change occurs
So how do you know if a chemical equation is
balanced? You need to count up the number of
each type of element on both sides of the
.
2H2O2
2H2O + O2
4 H and 4 O
4 H and 4 O
This equation is balanced because it has the
same number of each element on both the
reactants and the products side.