Download A = Atomic Number

Atomic Structure
Atoms are made of 3 subatomic particles:
proton, neutron, electron
NAME
WHERE
FOUND
Protons Nucleus
ELECTRIC
CHARGE
Positive (+)
SIZE
IMPORTANCE
1 amu
Determines the identity
of an element
Number of protons is
the atomic number
Neutrons Nucleus
No Charge
1 amu
Electrons Somewhere
Negative (-)
1/1836 amu
Determines (w/ protons)
the mass of the atom
Determines how atoms
reacts with other
atoms
Each energy level in the
electron cloud can hold
a limited # of electrons
in the
Electron
Cloud-exact
location
unknown
Atoms

AMU = Atomic Mass Unit. It is the size of a
proton. It takes
600,000,000,000,000,000,000,000 protons
to make 1 gram.

Atoms are electrically neutral. This is
because an atom has the same number of
protons (positive charges) as electrons
(negative charges)
Chemical Symbol

An abbreviation that represents the name of
an element
 The
chemical symbol can contain 1 or 2
letters. The first letter is always capitalized.
The second letter is lower cased.
 Ex.:
 Hydrogen
=H
 Silicon - Si
Atomic Number



Remember: Make an
A+, you’re #1!
Atomic number is the
number of protons in an
element. It identifies the
element.
If you change the
number of protons, you
change the element.
Mass Number

Mass Number- Equal to the number of protons + the
number of neutrons in an atom.
MASS NUMBER = # PROTONS + # NEUTRONS

We can use the mass number to find the number of
neutrons an element has.

To find the number of neutrons in an atom, subtract the
atomic number from the mass number.
# NEUTRONS = MASS NUMBER - ATOMIC NUMBER
Atomic Mass

Atomic Mass: The
average mass of all
known isotopes of an
element. This is
found on the periodic
table.

Isotopes are the
elements that have
atoms with different
numbers of neutrons,
so a different mass
number
Isotopes
Mass Number
Atomic Number
2
1
H
Chemical Symbol
Ex.: Hydrogen Isotopes
Isotope
Name
1
1H
Protium
2 H
1
Deuterium
3
1H
Tritium
(Hydrogen-1)
(Hydrogen-2)
(Hydrogen-3)
Mass Number
*Because the mass number is different for each isotope of hydrogen, the number of neutrons in each
atom is different. The number of protons, however, is the same.
Reading an element tile on the
periodic table
Copy Tile and Labels
11
Na
Sodium
22.990
Atomic Number
(Number of Protons &
Number of Electrons)
Chemical Symbol
Element Name
Atomic Mass (Average
Mass of All Known
Isotopes)
Atoms and APEMAN

APEMAN = A way to remember all parts of an
atom
A = Atomic Number
P = Protons
E = Electrons
M = Mass Number
-A = Atomic Number
N = Neutrons
Atoms and APEMAN

Example:
A = Atomic Number
P = Protons
E = Electrons
M = Mass Number
-A = Atomic Number
N = Neutrons
Sodium-23
11
11
11
23
-11
12
Copy and Complete the Table
Below
Isotope
Name
Isotope Atomic Mass
#P
Symbol Number Number
#N
#E
16
16
16
Iron- 56
K
39
Copy and Complete the Table
Below
Isotope
Name
Isotope Atomic Mass
#P
Symbol Number Number
Iron- 56
56
Fe
26
56
16
32
19
39
26
#N
30
#E
26
26
Sulfur- 32
32
S
16
16
16
16
Potassium39
39
K
19
19
20
19