1. Mini-Lessons
The Atom

2. Mini-Lesson: Parts of the Atoms

3. What is an atom made of? Protons Neutrons Electrons 1amu=1.7 * 10-24 g
+1 Charge
1 amu (atomic mass unit)
1amu=1.7 * g
Neutrons
0 (neutral) charge
1amu
Electrons
-1 Charge
Found around the nucleus in an electron cloud
Virtually no mass
The protons and neutrons are located within the nucleus. It has very little volume but almost all of the mass of the atom so it is VERY dense!

4. What’s in The Box? Zr is Zirconium
Element Symbol
Zr is Zirconium
Atomic Number- tells the number of protons in one atom of the element
Zr has 40 Protons
(therefore it also has 40 electrons)
Atomic Mass (Mass Number)
Tells number of protons and neutrons combined (40 + ? = 91)

5. Elements And Their Atoms
Each element has a unique atomic number
The number of protons for an element’s atom is constant and unique
The number of electrons will equal the number of protons UNLESS the atom is an ion
An element’s atom can have a different number of neutrons
Since the mass of an atom depends on the protons and neutrons, the mass of an element can change
To find neutrons, subtract the atomic # from the atomic mass

6. Mini-Lesson: Isotopes and Ions

7. What is the Charge of an Atom?
In a typical atom you will have the same number of protons and electrons, what charge does this give the atom?
0 Charge, or it is neutral!

8. Can a proton leave an atom??No
If it did you would have a NEW element…more on this later!

9. Can an electron leave or join an atom??
Yes!
This is called an Ion
If the atom is missing an electron it will be a Positive Ion.
If the atom gains and electron it will be a Negative Ion.

10. Can the number of neutrons change?
Yes!
This is called an isotope, it will cause the MASS of the atom to change

11. For Example… Look at the periodic table and find Carbon
What is the atomic number?
What is the mass number?
“Carbon 12” is the most common form of Carbon
But you’ve heard of Carbon 14…That is an isotope of Carbon – it has two more neutrons, adding 2 amu to its mass…but it still has only 6 protons
To name an Isotope
Element Name – Mass #

12. Isotope of Different Element
Element D has 6 protons and 7 neutrons
Element F has 7 protons and 7 neutrons
Different Element
Element J has 27 protons and 32 neutrons
Element L has 27 protons and 33 neutrons
Isotope
Element T has an atomic number of 20 and an atomic mass of 40.
Element Z has an atomic number of 20 and an atomic mass of 41.

13. Mini-Lesson: Electron Arrangement and Bohr Model

14. Characteristics of Electrons
Extremely small mass
Located outside the nucleus
Moving at extremely high speeds in a sphere
Have specific energy levels
LecturePLUS Timberlake

15. Energy of Electrons
When atoms are heated, bright lines appear called line spectra
Electrons in atoms arranged in discrete levels.
An electron absorbs energy to “jump” to a higher energy level.
When an electron falls to a lower energy level, energy is emitted.
LecturePLUS Timberlake

16. Electrons have special rules….
You can’t just shove all of the electrons into the first orbit of an electron.
Electrons live in something called shells or energy levels.
Only so many can be in any certain shell.
The electrons in the outer most shell of any element are called valance electrons.
Created by G.Baker

17. Electron Levels (Shells)
Contain electrons that are similar in energy and distance from nucleus
Low energy electrons are closest to the nucleus
Identify by numbers 1, 2, 3, 4, 5, 6…..
The first shell (1) is lowest in energy, 2nd level next and so on 1<2<3<4
LecturePLUS Timberlake

18. Atom Models
There are two models of the atoms we will be using in class.
Bohr Model
Lewis Dot Structure
Created by G.Baker

19. Bohr Model The Bohr Model shows all of the particles in the atom.
In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.
In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. - + + -
Created by G.Baker

20. Nucleus 1st shell 2nd shell 3rd shell
Adapted from
Created by G.Baker

21. Order of Electron Filling
All electrons in the same energy level have similar energy.
Shell electrons
Shell electrons
Shell electrons (8 first, later 10)
Order of filling for the first 20 electrons
Shell
2e 8e 8e 2e
LecturePLUS Timberlake

22. So let’s try it…. Li Lithium How to draw a Lithium atom
First, look at the Periodic Table
Second, determine the number of protons the atomic number)
Then determine the number of neutrons (Atomic mass – atomic number)
Then determine the number of electrons the atomic number) 3 Li
Lithium 7
Created by G.Baker

23. So let’s try it…. Li Lithium Protons = 3 3 7 Neutrons = 4 (7-3=4) - +
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
Created by G.Baker

24. Mini-Lesson Forces in the Atom The Fantastic Four!

25. What Forces Keep an Atom Together
What Forces Keep an Atom Together ?   There are four natural forces that are responsible for the behavior of an atom’s particles The Fantastic Four!

26. Forces In The Atom Gravitational Force Electromagnetic Force
Attractive force between all objects in the universe
Gravity depends upon mass of and distance between objects…
This force is not very strong in the atom
Electromagnetic Force
Opposites attract; likes repel
Protons & electrons
Electrons and Nucleus

27. More Forces in the Atom Strong Force
Holds protons and neutrons together to make the nucleus
Greater than electromagnetic force between protons (since the protons would repel each other)
Weak Force – Yes, it’s a very weak force
Deals more with radioactive decay and nuclear fusion
Weak forces are important because they are responsible for stabilizing particles through the process of radioactive decay, in which a neutron in the nucleus changes into a proton and electron.

28. Mini-Lesson Groups, Periods, and The Lewis Dot Structure

29. Lewis Dot Structure O •• • • • •
The Lewis Dot Structure is a bit different from the Bohr model.
It only shows the element symbol and it’s outer most electron shell, the valence electrons. + - •• O • • • •
Created by G.Baker

30. The Periodic Table
Columns are called groups or families, and as family members, they have similar properties
Rows are called periods. They do not share properties, but properties change as one goes from left to right

31. The Periodic Table

32. The first element in a period
is always an extremely active solid.
The last element in a period is always
a particularly inactive gas. These are referred to as the “noble gases.”