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The Atom
An atom is the smallest particle of matter that still has the same properties of that element.
What is an atom?
Atoms = Building Blocks
Na
Mg
H
1. Protons Positively charged particles inside the nucleus
What makes up an atom?
2. Neutrons Neutrally charged particles inside the nucleus
3. Electrons Negatively charged particles outside the nucleus
Atomic Number: tells the number of protons in the nucleus.
Each element is unique- no two elements have the same number of protons/ atomic number.
Counting Atoms
Mass number: tells the total number of particles in the nucleus.
Mass # = #p + #n
Helpful Information
How to read the Periodic Table
How to write symbols
11
Na
22.989770
Atomic #
Element Symbol
Average Atomic Mass
Mass #
X11Atomic #
Example 1
Element
Atomic #
Mass # # proton
s
# neutro
ns
# electro
ns
symbol
Oxygen 8 16 8 8 8 16
8O
P + N = Mass8 + N = 16N = 8
# electrons = # protons
Example 2
Element
Atomic #
Mass # # proton
s
# neutro
ns
# electro
ns
symbol
3 7 4 3 7
3Li
P + N = Mass3 + N = 7N = 4
If the atomic # is 3, look at the PT to find out which element is 3
The atomic # tells us the # p in the nucleus
3Lithium
Example 3
Element
Atomic #
Mass # # proton
s
# neutro
ns
# electro
ns
symbol
22 18 40
18Ar
P + N = Mass18 + N = 40N = 22
If the symbol is Ar, the element name is Argon
From the symbol, the top number is 40 (mass #)
From the symbol, the bottom number is 18 (atomic #)
The atomic # tells us the # p in the nucleus
184018Argon
# electrons = # protons