1. Atomic Structure
Concepts

2. The 3 particles of the atom:

3. Subatomic Particles Particle Symbol Charge Relative Mass
Electron e- neg. (-) 0
Proton p+ pos. (+) 1
Neutron n

4. The # of electrons determines the electrical charge of the element.
Subatomic Particles
The # of protons in one atom of an element determines the atom’s identity.
The # of electrons determines the electrical charge of the element.

5. Subatomic Particles
The atomic number tells you the number of protons in one atom of an element.
It also tells you the # of electrons in a neutral atom of that element.
The atomic number gives the “identity” of an element as well as its location on the periodic table.
No two different elements will have the same atomic number.

6. Atomic Number on the Periodic Table11 Na
Atomic Number
# of protons
&
# of electrons
Symbol

7. Subatomic Particles
The atomic mass of an element is the average mass of an element’s naturally occurring atom, or isotopes, taking into account the percentage of each isotope.
The atomic mass of an element is the total number of protons and neutrons in the nucleus of the atom.

8. Atomic Mass on the Periodic Table11 Na 23
Atomic Number
Symbol
Atomic Mass

9. Subatomic Particles
The mass number is used to calculate the number of neutrons in one atom of an element.
In order to calculate the number of neutrons you must subtract the atomic number from the atomic mass.

10. Calculating Mass Number
Isotopic Symbol 11 Na 23 23 Na 11
23 – 11 = 12
Mass Number