1. # of Subatomic particles Atomic Mass - calculate
What’s inside?
Properties
The Atom
Periodic Table
# of Subatomic particles
Atomic Mass - calculate

2. Contains 99.9% of the mass of the atom.
WHAT’S INSIDE
NUCLEUS
The “core” of the atom.
Contains 99.9% of the mass of the atom.
ELECTRON CLOUD
Area around the nucleus.

3. SUBATOMIC PARTICLES PROTON Located in the nuceus Charge – positive
Mass = 1 amu (atomic mass unit)
Neutron
Located in the nucleus
Charge – neutral
Mass – 1 amu (atomic mass unit)
ELECTRON
Located outside the nucleus in the “electron cloud”
Charge – negative
Have very little mass x 10⁻28 g/ 0 amu

4. PROPERTIES OF ATOMS OF DIFFERENT ELEMENTS
What makes one atom different from another?
The number of subatomic particles in the atom.
Gold
Mercury

5. PERIODIC TABLE INFORMATION
ATOMIC NUMBER:
The number of protons located in the nucleus of the atom.
Identifies the element
Will never change!!!
MASS NUMBER:
How many protons and neutrons are in the nucleus of the atom.
Protons + Neutrons = Mass #

6. DETERMINING NUMBER OF SUBATOMIC PARTICLES
Element
Number of Protons
Number of Electrons
Number of Neutrons
Atomic Number
Mass Number
Manganese 25 30
Sodium 11 12
Bromine 35 45
Yttrium 39 89
Arsenic 33 75
Actinium
227
Protons:
Same as the atomic #.
Neutrons :
Mass # - Atomic #
Electrons:
Same as the # of protons

7. Number that shows on the periodic table.
AVERAGE ATOMIC MASS
Number that shows on the periodic table.
Average of all the isotopes of an element.
An isotope is an atom that has the same number of protons but differing numbers of neutrons, changing the mass of the atom.

8. CALCULATING ATOMIC MASS
Determine the mass contribution of each isotope of the element.
(relative abundance x mass of isotope)
Add the mass contributions together.
Note that you do not divide!!
Use significant figures in rounding answer.