1. Atom Basics

2. The Subatomic Particles
Protons (p+) :
Have +1 Charge
Have a mass of 1 amu (atomic mass unit)
Electrons (e-):
Have a -1 charge
Have a mass of amu
Neutrons (n0):
Have no charge
Have a mass of 1 amu

3. Atomic Structure
FAIL

4. Electron Cloud Model Nucleus Rest of the atom Incredibly small
Contains all the protons and neutrons
Nucleus is very dense
Rest of the atom
Mostly empty space
The electrons move around in the empty space
No Specific Orbits
Use a cloud to show the probability of finding an electron = orbital

5. How do we describe atoms?
Every element has its own atomic number
Atomic number is on top in the blocks in the periodic table
Atomic Number = Z = number of protons

6. How do Protons and Electrons Relate?
If an atom has no charge then…
The number of electrons must equal the number of protons.
If the atom has a charge then its called an ion
Positively charged ions = cations
Negatively charged ions = anions

7. How do Protons and Electrons Relate?
How do atoms become charged?
Comes from imbalance in protons and electrons
Only the number of electrons changes
Protons are buried deep in the nucleus and so they don’t change.
Positive charge
Lost electrons
Negative charge
Gained electrons

9. What about neutrons? Imagine three atoms: What element are they?
Atom 1: 6 protons, 6 electrons, 6 neutrons
Atom 2: 6 protons, 6 electrons, 7 neutrons
Atom 3: 6 protons, 6 electrons, 8 neutrons
What element are they?
All the same element but the atoms aren’t the same
Isotopes – Atoms with the same number of protons but different numbers of neutrons

10. How do we tell the atoms apart?
Atom 1: 6 protons, 6 electrons, 6 neutrons
Atom 2: 6 protons, 6 electrons, 7 neutrons
Atom 3: 6 protons, 6 electrons, 8 neutrons
Mass Number = protons + neutrons
Symbol = A
Not every isotope is represented evenly.

11. How do we adjust for different isotopes?
Average atomic mass – weighted average of the masses of all the isotopes.
Bottom number on Periodic Table

12. Average Atomic Mass Carbon has two naturally occurring isotopes:
Carbon with a mass number of 12 – 98.93%
Carbon with a mass number of 13 – 1.07%
(12 amu * ) + (13 amu * ) = amu

13. What is the shorthand? X = symbol of the element A = mass number
Z = atomic number
Q = charge (left off if not charged)
Also see just X–A
C-13

14. Practice What is the atomic number? What is the atomic mass?
What is the mass number?
How many protons?
How many neutrons?
How many electrons?