1. Structure of the Atom Read Ch 19 from p578
Chapter 19 Section 1
Structure of the Atom
Read Ch 19 from p578

2. Scientific Shorthand Scientists abbreviate the names of elements
Each element has a nickname
1, 2 or sometimes 3 letters
First letter capitalized
Second and third letter would be lower case
Names of elements come from different sources
Latin names
Honoring scientists
Places
Properties of the element
Rules established by an international committee

5. Chemical Formulas

6. Atomic Components The atom is made up of different parts Protons
Large particles, found in nucleus
Positively charged
Neutrons
No charge
Electrons
Tiny particles, found outside of nucleus
Negatively charged

7. Quarks Atomic Particles
Theorized particles that make up protons and neutrons
6 different quarks have been discovered
The theory is that an arrangement of 3 quarks held together with a strong nuclear force produces a proton
The search for the components of protons and neutrons is an ongoing effort
Atomic Particles

8. Finding Quarks
To study quarks, scientists accelerate charged particles to tremendous speeds and then force them to smash into protons
Electric and magnetic fields are used to accelerate, focus, and smash the particles.
This causes the proton to break apart.
Particles from the collision are detected and reconstructed like crime scene data.

9. Models
There have been many changes to the model of the atom over history
It was not always known that all matter was composed of atoms
Aristotle disputed Democritus’ theory that matter is composed of smaller particles

10. Democritus Model Atom could not be subdivided
Named it atomos, meaning uncuttable

11. John Dalton Dalton offered proof that the atom existed
Dalton’s model was similar to Democritus
Dalton’s ideas gave a physical explanation for chemical reactions

12. Thomson Model - 1904 Electrons embedded in a positively charged sphere
Called the plum pudding model.

13. Rutherford Gold Foil Demonstration
Click on the following:

14. Rutherford Model
Almost all the mass of the atom in the center of the atom
All positive charge in the center of the atom

15. Bohr Model
Electrons travel in fixed orbits around the nucleus of the atom.
Chadwick concluded that the nucleus contained positive protons and neutral neutrons.

16. Electron Cloud Model - Current

17. Electron Cloud Model
Electron Cloud is the area around the nucleus where electrons are likely found.
Electron Cloud is 100,000 times larger than the diameter of the nucleus. Imagine a baseball field. An orange at the pitcher’s mound would be the nucleus and the rest of the field would be the electron cloud.
Electrons are moving so fast they are like spokes on a moving bicycle wheel.

19. Compare Protons and Neutrons
Large particles
Notes
Compare Protons/Neutrons
Large particles
Notes

20. Venn Diagram
Proton Neutron Electron

22. Ch 19.1 Analysis: 1 paragraph
List chemical symbols for the elements carbon, aluminum, sodium, and sulfur.
Identify the names, charges, and location of the 3 main kinds of particles in an atom
Identify the smallest particle of matter. How were they discovered?
Describe the electron cloud model of the atom.

23. Chapter 19 Section 2
Masses of Atoms

24. Atomic Mass Atomic Mass = mass of an atom
Unit of measurement is the amu
1 amu (Atomic Mass Unit) is almost equal to the mass of a single proton or neutron
Protons and neutrons are far more massive than electrons

25. Atomic Number Atomic Number = number of protons in an element
To keep atoms neutrally charged, number of protons equals the number of electrons
So, Atomic Number = number of protons = number of electrons

26. Mass Number
The Mass Number can be used to find the number of neutrons in an element.
Mass Number = sum of protons and neutrons
Neutrons = Mass Number – Atomic Number

27. Isotopes Not all atoms have the same number of neutrons
Atoms of the same element with different numbers of neutrons are called isotopes
If there is a different number of neutrons, the mass number will be different

28. Identifying Isotopes
Average atomic mass is the weighted average mass of the mixture of isotopes
This is why mass number is not usually a whole number
A number is given to identify different isotopes
Like Boron-10 and Boron-11

29. Periodic Table of Elements
Organized chart of the elements
Elements are in order by atomic number
Also arranged by differences in physical and chemical properties
Groups or Families in vertical columns have elements with similar properties.
Periods are in horizontal rows.

30. Dmitri Mendeleev
Father of the periodic table noticed trends in elements that were periodic, or repeated.
Arranged the first periodic table by atomic mass in 1869.
Left blanks for missing elements AND predicted their properties.

32. Henry Mosely Mosely made some changes to the periodic table
He arranged all atoms by increasing atomic numbers instead of atomic masses

34. Electron Cloud Structure
Electrons within the electron cloud have different amounts of energy
The closer an electron is to the nucleus, the less energy it has.
Elements in a group have same number of electrons in the outer valence energy level
This determines properties of the elements

35. Electron Dot Diagram
The outer shell is important in determining chemical properties of elements.
Electron dot structures use dots around the symbols of the elements to represent the electrons in the outer shell.
Electron dot structures can also be used to show how elements bond.

36. Valence Electrons
Valence electrons are the electrons in the highest occupied energy level of the atom. Usually they are in the outer shell.
Valence electrons are the only electrons generally involved in bond formation.

37. Groups and Periods
Each element in a Group or Family column has the same number of valence electrons in their outer energy level.
Generally, each Period row represents an energy level where electrons may be found

38. Energy Levels 1 – 7 (p592)
Atoms want to be stable by filling their electron energy levels.
The 1st energy level nearest the nucleus may contain a maximum of 2 electrons.
The 2nd and 3rd energy levels may contain a maximum of 8 electrons.
Beyond that, energy levels may contain 18 or even 32 electrons.

39. Lewis Electron Dot Diagram
A Dot Diagram simply shows valence electrons around the element symbol.

40. Create Dot Diagrams Find the Group column the element is in.
This tells the number of valence electrons.
Write the symbol and then draw valence electrons around it, starting at 3 o’clock and going counterclockwise to 12, 9, & 6. Continue around one more time if needed.
Draw dot diagrams for Cl and C.

41. Dot Diagram Solution 1
Chlorine and Carbon should look like this:

42. Dot Problem 2
Use the Periodic Table to find the number of valence electrons to complete the chart.
Draw the chart, symbols and dots needed. Follow pattern above starting at position 1. 1A 2A 3A 4A 5A 6A 7A 8A H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Ga Ge As Se Br Kr

43. Dot Diagram Solution 2
Elements in the same Group have the same valence electron dot structure.

44. Dot Diagrams for Bonds
A chemical bond might looks like this:

45. Definitions Alloy: solid solution (mixture) of metals
Aluminum: most abundant metal in Earth’s crust
Conductive: able to transfer materials like heat (thermal) and electricity easily
Ductile: able to be stretched (drawn) into wire
Ion: charged atom from electrons gained or lost
Luster: shiny and able to reflect light
Malleable: able to be shaped by hammer
Oxidation: rust caused by reacting with oxygen
Oxygen: most abundant element in Earth’s crust

46. Helpful Tips A# = PorE: Atomic Number = Protons or Electrons
NoP = E: Number of Protons = Electrons
PaN = MaN: Protons and Neutrons = Mass Number

47. Ch 19.2 Analysis: Make Tables
Use Periodic Table to find the name, atomic number, and atomic mass of the following elements: N, Ca, Kr, and W.
List the period and group where these elements are found: nitrogen, sodium, iodine, and mercury.
Give the name & classify each as metal, nonmetal, or a metalloid: K, Si, Ba, and S. See tables on next slide.

48. Ch 19.2 Analysis: Draw & Complete Tables
Symbol
Name
Atom Number
Atom Mass N Ca Kr W
Name
Period ↔ Row
Group ↨ Column
Nitrogen
Sodium
Iodine
Mercury
Symbol
Name
Metal
Non-Metal
Metalloid K Si Ba S