1. Today Atomic particles electrons, protons, neutrons
Found inside the nucleus
Atomic mass and atomic number

2. electron
neutron
proton

3. What is the structure of an atom?
Nucleus – center of the atom
Home of Protons and Neutrons
Proton
Has a positive (+) charge
Has a relative mass of 1
Determines the atomic number
Found inside the nucleus P

4. What is the structure of an atom?
Neutron
Has no (0) charge
Has a relative mass of 1
Determines the isotope
Isotopes are two of the same element with different masses
Found inside the nucleus N

5. What is the structure of an atom?
Electron
Has a negative (-) charge
Has a relative mass of 0 (zero)
Determines the ion
Found outside the nucleus
Bohr model – electrons are in specific energy levels
Electron cloud model – electrons are in a random cloud e

6. What is the structure of an atom?
Bohr Model
“Planetary Model”
Schrödinger Model
“Electron Cloud Model”

7. How are P, N, e- related? # protons = atomic number
# electrons = # protons in a neutral atom
# protons + # neutrons = atomic mass

8. Properties and atomic number
Scientists discovered that the properties of elements seemed to depend on atomic number.
What is the atomic number of an element?
Atoms contain three types of particles:
particle
charge
relative mass
proton +1 1
neutron
electron -1
0.0005
Where are these particles found in an atom?

9. What is atomic number? neutron electron helium nucleus proton
What are the particles in this helium atom?
neutron
electron
helium
nucleus
proton
Atomic number = the number of protons in an atom
What is the atomic number of helium?

10. Atomic number and electrons
Atoms of elements contain equal numbers of protons and electrons.
How does this affect the charge of such atoms?
Atoms of elements have no charge, they are neutral.
What is the charge on a fluorine atom? 19 F 9
9 protons
9 electrons
10 neutrons
charge = +9
charge = - 9
charge = 0
total charge = 0
How are the number of electrons and atomic number related in a neutral atom?
They are the same.

11. What is a chemical symbol?
Chemical symbol tells us what atom it is
Always a CAPITAL LETTER, sometimes followed by a lower case letter
Ex: Oxygen O Nitrogen N Sodium Na
*Cobalt – Co *Carbon Monoxide – CO
(Co is an element, CO is a compound)

14. Charge (if ion)
Atomic Number
Symbol
Atomic Mass

15. Hydrogen
Protons: 1
Neutrons: 0
Electrons: 1 H 1 1

16. Sodium
Protons: 11
Neutrons: 12
Electrons: 11 Na 23 11

17. Rhenium
Protons: 75
Neutrons: 111
Electrons: 75 Re
186 75

18. Rhenium isotope
Protons: 75
Neutrons: 112
Electrons: 75 Re
187 75

19. Cs 133 55 EXAMPLE Atomic number = protons and electrons
How many protons, neutrons and electrons are found in an atom of
133 55 Cs
Atomic number = protons and electrons
There are 55 protons and 55 electrons
Mass number = sum of protons and neutrons
133 – 55 = 78
There are 78 neutrons

20. Symbols
Contain the symbol of the element, the mass number and the atomic number. 20

21. Symbols
Contain the symbol of the element, the mass number and the atomic number.
Mass
number X
Atomic
number 21

22. F Symbols 19 9 Find the number of protons number of neutrons
number of electrons
Atomic number
Mass Number 19 F 9 22

23. Br Symbols 80 35 Find the number of protons number of neutrons
number of electrons
Atomic number
Mass Number 80 Br 35 23

24. Symbols
if an element has an atomic number of 34 and a mass number of 78 what is the
number of protons
number of neutrons
number of electrons
Complete symbol 24

25. Symbols if an element has 91 protons and 140 neutrons what is the
Atomic number
Mass number
number of electrons
Complete symbol 25

26. Symbols if an element has 78 electrons and 117 neutrons what is the
Atomic number
Mass number
number of protons
Complete symbol 26

29. Why do atoms lose or gain electrons?
Atoms give and take electrons to be stable.
All atoms wants to have as many electrons as their nearest groups 18 atoms