1. ELECTRON CONFIGURATION
REVIEW FROM UNIT 6
CHAPTER 18.3

2. Electron Configuration
Electrons are organized on the outside of the atom in orbitals.
An orbital is a region of space around the nucleus of an atom where an electron is likely to be located.
They move like planets around the sun.
Each electron in an atom has a specific amount of energy and the energy of an electron can change.

3. Energy Levels
The possible energies an atom can have are called energy levels.
An electron in an atom can move from one energy level to another when the atom gains or loses energy.
Staircase analogy
The level closest to the nucleus that has the least energy has the lowest number of electrons, 2.

6. Energy Levels
An electron configuration is the arrangement of electrons in the orbital of an atom.
The most stable electron configuration is the one in which the electrons are in orbits with the lowest possible energy.

7. Valence Energy Level
A valence electron is an electron that is in the highest occupied energy level of an atom.
These electrons play a key role in chemical reactions.
Elements in a group have similar properties because they have the same number of valence electrons.
(Hydrogen location on periodic table)
When the highest occupied energy level is full an atom is stable. (HAPPY.)

9. BONDING AND DOT DIAGRAMS
CHAPTER 19.1

10. Electron Dot Diagram
An electron dot diagram is a model of an atom in which each dot represents a valence electron.
The symbol in the center represents the nucleus of and all other electrons in an atom.

14. Stable Electron Configurations
When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react.
Noble gases

15. Chemical Bond
Elements that do not have a complete set of valence electrons tend to react with another element to achieve complete electron configurations.
They do this by “bonding”. A process of sharing or giving/taking electrons.
A chemical bond is the force that holds atoms together as a unit.

17. Octet Rule
You have a complete set of valence electrons when you fulfill the Octet rule.
The octet rule states that the element has eight valence electrons.
In other words the valence is FULL!
Sometimes this can only happen if two elements bond together.

20. Ionic Bonds
An ionic bond is a type of bond created with electrons are transferred from one atom to another.
Give and Take
Usually metal to non-metal
This process can create IONS.
Bond is possible because opposite ions attract

23. Covalent Bond
A covalent bond is a bond where two atoms share a pair of valence electrons
Polar - has oppositely charged ends
Non-polar – ends are charged the same
Bond is possible b/c protons attract to shared electrons

24. CHEMICAL FORMULAS
Notes 19.2 and 19.3

25. Chemical Formula The short-cut way of writing a compounds name.
Chemical formula shows the symbol and the ratio of atoms by using subscripts.
For Example:H2O

26. Oxidation Numbers
An oxidation number indicates how many electrons are lost, gained or shared when bonding occurs.
When writing the oxidation number the charge symbol is written after the number.
For Example: 3+

28. Groups 3-12
Are special.
They have many different oxidation numbers.

30. Writing Chemical Formulas for Ionic Compounds
Use the name of the compound to identify the symbols of the elements.
Using the periodic table, assign oxidation numbers to each element or group.
Put the ions in the correct order.
Cation first, Anion second.
Criss Cross the oxidation numbers to identify how many atoms of each element are needed to make a neutral compound.

31. Ion
An Ion is an atom that has a net positive or negative electric charge
Anion – An ion with a negative charge
Cation – An ion with a positive charge

33. Writing a Chemical Formula for Covalent Compounds
Use the same procedure.
Only change Metal is written first (least electronegative), Nonmetal is written second (more electronegative).
Identify the type of covalent compound.
Polar - has oppositely charged ends
Non-polar – ends are charged the same

34. Transition Metals (Group 3-12)
When writing a chemical formula that includes a transition metal, you must use a reference table.
The oxidation number of the transition metal is represented in the name of the compound using roman numerals.

36. Polyatomic Ions Sometimes a group of ions act as one atom.
They have only one charge for their group.
You do not need to memorize these special ions, they will always be available for you in a reference table.

37. Polyatomic Ions

38. Writing a Chemical Formulas for Ionic Compounds with Polyatomic Ions!
The same process applies as writing an ionic compound.
Use the criss-cross method for ease.
Keep the polyatomic ion together, using parenthesis if necessary.

40. Formula Mass
The mass of one molecule of a compound relative to the mass of other compounds.
Add up the mass of all the atoms in a chemical formula for a total mass.

42. HOW TO NAME A COMPOUND
Notes 19.2

43. Naming Ionic Compounds
Identify the formula of the compound.
Identify which element is written 1st / 2nd.
Write the full name of the first ion.
Exception: Transition Metals
Write the name for the second ion.
Element- Change ending of element to –ide.
Polyatomic Ion- Write full name.

44. CHEMICAL CHANGES
Notes 20.1

45. Comparison of Physical and Chemical Properties

46. Physical Property
Any characteristic of a material that can be observed or measured without change in the composition of the substances in the material.
Properties include:
Size
Shape
State
Ex. Braiding Hair / Cutting Hair

47. Examples of Physical Properties

48. Using Physical Properties to Separate Mixtures
Filtration: a process that separates materials based on the size of their particles.
Distillation: A process that separates materials based on their boiling points.

49. Chemical Properties
Can be observed only when the substances in a sample of matter are changing into different substances.

50. Is a Change Chemical or Physical?
When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.

51. Changes… Physical Ice to Water to Steam Chemical
Flammability, Reactivity
Change in color
Production of a gas
Formation of a precipitate

52. CHEMICAL EQUATIONS
Notes 20.2 and 20.3

53. Chemical Equations
A short hand method of representing a chemical reaction.
REACTANTS: The materials with which you start the reaction.
PRODUCTS: The materials that are created by the reaction.

54. Symbols Symbol Meaning  Produces + Plus (cr) Crystalline solid (l)
Liquid
(g)
Gas
(s)
solid

55. Conservation of Atoms
The quantity of each type of atom you start a reaction with must be equal to the quantity and type of atoms you have when the reaction is over.
Reactants = Products

56. Balancing Equations
If this principle is not met in an equation, the equation must be balanced.
You can add a coefficient to formula’s in the equation to help achieve conservation of atoms.

57. Coefficients
Coefficients are numbers that represent the quantity of each substance taking part in the reaction.
You only show a coefficient in an equation if the number is greater than 1.

59. Law of Conservation of Mass
Not only do the quantity of atoms before and after a reaction have to be equal, but also the mass of the products must be equal to the mass of the reactants!

60. BALANCING EQUATIONS
Notes 20.2

63. Examples on Overhead Projector…..