2. Models of Matter:
Atomic Structure

3. subatomic electron proton neutron nucleus neutral
OUTCOME QUESTION(S):
S1-2-02:
What is the basic subatomic structure of an atom?
S1-2-04
How do you use atomic mass and atomic number to identify parts of the atom?
Vocabulary & Concepts 
subatomic electron proton
neutron nucleus neutral
Amu (µ) atomic mass atomic number

4. Subatomic – a fundamental particle smaller than an atom.
Experiments proved 3 subatomic particle:
Electron (e-): Small, negative electric charge
Proton (p+): Positive electric charge
Neutron (no): NO charge, same size as protons
Scientists have since found many more fundamental particles – many by crashing particles into each other to see the little pieces in the collision
Subatomic – a fundamental particle smaller than an atom.

5. Electrons occupy the space around the nucleus.
The protons and neutrons are found in the dense centre of the atom – nucleus.
Electrons occupy the space around the nucleus.
Atoms contain an equal number of (+) charged protons and (-) charged electrons.
Overall atom is neutral.

6. The number of protons in an element does NOT change.
Important points:
The number of protons in an element does NOT change.
No TWO elements have the same number of protons.
Atoms can lose and gain neutrons and electrons – since protons have NEVER been shown to change we use this to identify elements

7. Atomic Number
Atomic Mass
This information on the Periodic Table will help us build atomic models of any element

8. Atomic Number
Smaller value – no units
Equals the number of protons in the nucleus
p+ number is used to identify an element
Remember atoms are neutral (equal p+ and e-): Atomic number can be the number of protons OR electrons in the atom

9. How many protons and electrons in Carbon? Copper?
Atomic Number
How many protons and electrons in Carbon?
Copper?
6 protons and 6 electrons
29 protons and 29 electrons

10. Amu is just a unit to measure very small masses equal to
Protons (p+) have mass of 1 Atomic Mass Unit (μ)
Neutrons (no) are the same size - also 1 μ
Electrons (e-) are so small - considered zero mass
So ALL of the mass of an atom comes from the protons and neutrons only.
Amu is just a unit to measure very small masses equal to
x grams +
Protons
Neutrons -
electrons

11. Larger value – total mass in amu (μ) - Round off the value
Atomic Mass
Larger value – total mass in amu (μ)
- Round off the value
Equals total number of p+ and no in the nucleus
Since protons and neutrons each weight 1 amu – for Helium, a mass of 4.00 reveals there must be a total number of 4 subatomic particles in the nucleus

12. Atomic Number Atomic Mass
(Protons/Electrons) (Protons + Neutrons)
PROTONS
Atomic Number = 2
NEUTRONS
A.mass – A.number = 4 – 2 = 2
ELECTRONS
Same as Protons = 2

13. Sulfur (S)
How many protons are there in one atom of Sulfur?
Atomic number p+
How many electrons in one atom of Sulfur?
Atoms are neutral e-
How many neutrons in one atom of Sulfur?
Atomic mass = 16 no
How many protons in 3 atoms of Sulfur?
3 x 16 = 48 p+

14. An atom is found with 19 protons:
What element is this?
Potassium
How many electrons in one atom of Potassium?
Atoms are neutral – 19 e -
How many neutrons in one atom of Potassium?
At mass – At number 39 – 19 = 20 no
How many protons in 10 atoms of Potassium?
10 x 19 p + = 190 p +

15. CAN YOU ANSWER THESE QUESTIONS? S1-2-02:
What is the basic subatomic structure of an atom?
S1-2-04
How do you use atomic mass and atomic number to identify parts of the atom?
Vocabulary & Concepts 
subatomic electron proton
neutron nucleus neutral
Amu (µ) atomic mass atomic number

16. Models of Matter:
Bohr Diagrams

17. orbit Bohr Diagram valence
OUTCOME QUESTION(S):
S1-2-05
How do you draw an atom using the Bohr model?
Vocabulary & Concepts 
orbit Bohr Diagram valence

18. THE ATOM Nucleus (p+): Positive (no): NO charge Surrounding
(e-): Small, negative

19. Emitted light was from excited electrons
Niels Bohr (1913)
“Flame Test” experiments show heated elements emit a unique pattern of colour.
This unique colour signature can be used to identify elements in mixtures or compounds
Emitted light was from excited electrons
Colour
Element
green
copper
red
strontium
purple
potassium
lavender
Lithium
yellow
sodium

20. Only a specific number of electrons fill each orbit
Hypothesis:
Electrons move in organized circular paths of different distances around a nucleus.
Orbit: location of electron motion around a
nucleus.
Only a specific number of electrons fill each orbit
Bohr reasoned that random electron movement cannot produce the same unique colour pattern EVERY TIME

21. Bohr’s model is called the “planetary” model
ORBITS:
1st – holds two electrons (e-)
2nd – holds eight e-
3rd – holds eight e-
Electrons occupy the closest orbital first
Elements have a different number of electrons

22. Use the atomic mass and atomic number to find the information (p+, no, e-) to build Bohr atomic models

23. Drawing a Complete Bohr Atom:
Determine the number of no, p+, e- in the atom.
Draw the nucleus.
Label the #of protons and neutrons.
Add orbits and fill with the appropriate # of e-.
Nitrogen (N)
p+ : 7
no : 14 – 7 = 7
e- : 7
7p+
7no

24. Remember the first shell can only hold 2 electrons before being “full”
Lithium (Li)
p+ : 3
no : 7 – 3 = 4
e- : 3
Remember the first shell can only hold 2 electrons before being “full”
3p+
4no

25. Sodium (Na) p+ : 11 no : 23 – 11 = 12 e- : 11 11p+ 12no
Putting electrons around in pairs at the quadrants makes it easier to count later
11p+
12no

26. Last (outer) atom orbit
Valence:
Last (outer) atom orbit
All electrons in last orbit - valence electrons
The number of valence electrons an atom has determines how the atom chemically reacts

27. Hydrogen has a total of 1 e- (1 valence e- )
Boron has a total of 5 e- (3 valence e- )
Neon has a total of 10 e- (8 valence e- )

28. CAN YOU ANSWER THESE QUESTIONS? S1-2-05
How do you draw an atom using the Bohr model?
Vocabulary & Concepts 
orbit Bohr Diagram valence