1. ATOMIC STRUCTURE
Ted Talks Atomic Theory Review

2. (greek for indivisible)
HISTORY OF THE ATOM
Democritus develops the idea of atoms
460 BC
He pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called
ATOMOS
(greek for indivisible)

3. MAJOR CONTRIBUTIONS & POINTS
HISTORY OF THE ATOM
SCIENTIST
MODEL OF THE ATOM
MAJOR CONTRIBUTIONS & POINTS
 DALTON (1803)
AKA: Billard Ball model
Matter is made of small particles called atoms.
1. Atoms are indestructible. They cannot be created or destroyed during chemical or physical changes.
Atoms of an element are identical. They have the same mass.
3. Atoms of different elements have different masses.
4. Compounds are formed by combining atoms of different elements.

4. Law of Conservation of Mass
8 X2Y
16 X
8 Y +
Law of Conservation of Mass
2.1

5. Law of Definite Proportions
The ratio of mass of elements in a compound is always the same
Every water molecule will contain 16g of oxygen and 2 g of hydrogen 1g 1g
16g
Total mass: 18g per water molecule

6. MAJOR CONTRIBUTIONS & POINTS
HISTORY OF THE ATOM
SCIENTIST
MODEL OF THE ATOM
MAJOR CONTRIBUTIONS & POINTS
 THOMPSON (1890’s)
 AKA: plum pudding model
discovers electrons (negative charge)
electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron’s charge
electrons

7. HISTORY OF THE ATOM SCIENTIST MODEL OF THE ATOM
MAJOR CONTRIBUTIONS & POINTS
RUTHERFORD (1909)
Gold foil experiment – alpha (+) particles were fired at Au foil:
FYI ONLY….If the atom is New Era Stadium
Then the nucleus is a marble on the 50 yard line
(1909 Nobel Prize in Chemistry)
Rutherford performed the following experiment: He aimed a beam of high speed, positively charged particles called alpha particles (similar to a tennis ball) at a piece of solid gold foil (similar to a wall). He set up a special screen all around the foil to help him see where the particles went.

8.
Results: 99% of the alpha particles went straight thru, 1% were deflected.
Findings::
1. Atom has a small, positively charged center
2. Atom is mostly empty space (consisting of negatively charged electrons)
2.2

9. MAJOR CONTRIBUTIONS & POINTS
HISTORY OF THE ATOM
SCIENTIST
MODEL OF THE ATOM
MAJOR CONTRIBUTIONS & POINTS
 BOHR (1913)
AKA: Planetary model
electrons move in definite, fixed orbits around the nucleus
each orbit only able to contain a set number of electrons.

10. MAJOR CONTRIBUTIONS & POINTS
HISTORY OF THE ATOM
SCIENTIST
MODEL OF THE ATOM
MAJOR CONTRIBUTIONS & POINTS
QUANTUM MODEL
(1930’s)
AKA: Wave Mechanical or Electron cloud model
Electrons have a distinct amount of energy and have wave-like properties.
They travel in regions called orbitals.
These regions are the most likely location of an electron.

11. Answers to pg 4 in packet:
1) A 2) C 3) B 4) C 5) D 6) C 7) D 8) A 9) A 10) A

12. HISTORY OF THE ATOM reviewed
Atomos song
Crash Course
Science Classroom

13. Atoms The basic unit of Matter
The smallest particle of an element that retains the properties of that element.
Made up of subatomic particles

14. ATOMIC STRUCTURE All About Atoms Particle Charge Mass Proton + charge
1amu
Neutron
No charge
1 amu
electron
- charge
1/1836

15. number of electrons = number of protons
ATOMIC STRUCTURE He 2
Atomic number
Represents the number of protons in an atom
Never changes
P+ equal to the number of e- 4
Mass Number
the number of protons and
neutrons in an atom
Neutrons equal
mass # - atomic #
number of electrons = number of protons

16. HELIUM ATOM + - + - Shell proton neutron electron
What do these particles consist of?

17. Isotopes
Atoms with the same atomic number but different mass number or
Atoms having the same number of protons but different numbers of neutrons
Which atom is an isotope of oxygen?
1). O 2). O ). O
Isotopic notation:
O or O-16 16 17 16 7 8 6 16

18. 2.3

19. CHEM DO…Do You Understand Isotopes?
1. Define an isotope
2. How many protons, neutrons, and electrons are in C 14 6 ?
6 protons, 8 (14 - 6) neutrons, 6 electrons
3. How many protons, neutrons, and electrons are in C 11 6 ?
6 protons, 5 (11 - 6) neutrons, 6 electrons
Isotope Maker
2.3

20. X H H (D) H (T) U Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
# OF NEUTRONS = mass number – atomic number
Mass Number X A Z
Element Symbol
Atomic Number H 1
H (D) 2
H (T) 3 U
235 92
238
2.3

21. Average Atomic Mass
Average Atomic Mass of an element is the weighted average of an element’s naturally occurring isotopes.
What is the average mass of cesium given the percent abundance of selected cesium isotopes?
75% Cs % Cs % Cs- 134
Practice: Guide pages 3 and 4
show work set up and solve

22. Bohr Model of the Atom (planetary model)
Energy Levels
Electrons revolve around the nucleus in one of several orbits/shells/ principal energy levels
Principal energy level (PEL) is the same as the period number on the periodic table
There are 7 PEL’s therefore 7 periods
PEL is designated by a quantum number (n)

23. Alkali Earth Metal
Noble Gas
Halogen
Alkali Metal
Period
Group
2.4

24. Location of electron
According to the Bohr model, electrons are found in shells around the nucleus
first shell maximum of 2 electrons
second shell maximum of 8 electrons
third shell max of 18 electrons
fourth shell max of 32 electrons

25. 1. Electronic Configuration
ATOMIC STRUCTURE
There are two ways to represent the atomic structure of an element or compound;
1. Electronic Configuration
2. Electron dot diagrams

26. ELECTRONIC CONFIGURATION
With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example;
Nitrogen
configuration = 2 , 5
2 in 1st shell
5 in 2nd shell 14 N 7
= 7

27. ELECTRONIC CONFIGURATION
Write the electronic configuration for the following elements; 20 11 8 Na O Ca a) b) c) 16 23 40
2,8,8,2
2,8,1
2,6 14 17 Si 5 Cl B d) e) f) 11 35 28
2,8,7
2,8,4
2,3

28. Valence
Valence shell is outermost occupied energy level and is the same as the period number in the periodic table
Valence electrons are the electrons in the outer energy level of an atom

29. N DOT & CROSS DIAGRAMS Nitrogen
With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X 14
Nitrogen X X N X X N X X 7

30. DOT & CROSS DIAGRAMS Cl O
Draw the Dot & Cross diagrams for the following elements; X 16 35 X Cl a) O b) X 8 17 X X X X X X Cl X X X X X X X O X X X X X X X X X X

31. 11 protons 11 protons 11 electrons 10 electrons 17 protons 17 protons
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons
2.5

32. How many protons and electrons are in
Do You Understand Ions?
How many protons and electrons are in Al 27 13 ? 3+
13 protons, 10 (13 – 3) electrons
How many protons and electrons are in Se 78 34 2- ?
34 protons, 36 (34 + 2) electrons
2.5

33. 2.5 A monatomic ion contains only one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4+, NO3-
2.5

34. SUMMARY The Atomic Number of an atom = number of
protons in the nucleus.
The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
The number of Protons = Number of Electrons.
Electrons orbit the nucleus in shells.
Each shell can only carry a set number of electrons.