1. QOD 9/19/12 Take out your notes or blank paper
What is the atomic number and mass of Carbon?

2. Chemistry Notes

3. Atomic Theory
The Atomic Theory of Matter states that all matter is composed of small, fast moving particles called atoms.
Atoms can join together to form molecules.
This theory is really thousands of individual theories that provide evidence for the whole theory.

4. What do they REALLY look like?
No one really knows for sure, so we make models!

5. Atomic Structure
Atoms are made of Subatomic particles

6. Subatomic Particles Particle Symbol Charge Relative Mass
Electron e
Proton p
Neutron n

7. Interesting facts…. Why is the relative mass of an electron 0??
Protons (relative mass 1) and neutrons (relative mass 1) have over 1800 times the mass of an electron (1/1836 relative mass)
If a proton or neutron had the mass of a gallon of milk, then an electron would have the mass of a dime!!

8. Parts of the Atom
Neutron
Orbital
Nucleus
Proton
Electron

9. Parts of the atom
Orbital- the part of the atom where the electrons are found, located around the nucleus
Nucleus- the middle part of the atom where the protons and neutrons are found.

10. Interesting fact….
An atom is mostly empty space because the electron moves around the nucleus at such a great distance. If the proton were 1 cm wide a hydrogen atom would be larger than a football field!

11. Parts of an Atom The Periodic Table of Elements
So, how do we know how many protons, neutrons and electrons are in an atom?
The Periodic Table
of Elements

12. Elements
An element is a pure substance that cannot be separated into different substances by ordinary processes
All known elements are listed in the Periodic Table of Elements
Examples:
carbon
gold
calcium

13. What information can be found in your periodic table?
Element Symbol
Element Name 6 C
Carbon
Atomic Number
Atomic Mass

14. Symbols of Elements
Symbols are used to represent elements in the periodic table
They are 1 or 2 letter abbreviations
Capitalize the first letter only
Examples:
C carbon Co cobalt
N nitrogen Ca calcium
F fluorine Br bromine O oxygen Mg magnesium

15. Atomic Number
A chemical element is determined based on how many protons the nucleus contains
(Hydrogen has 1, Carbon has 6, Oxygen has 8 protons).
This number is unique to a given element.
This number will be different for every element 6 C
Carbon

16. Atomic Mass
Total number of neutrons and protons found inside the atom
Remember, electrons have almost no mass, so they are not counted 6 C
Carbon

17. Calculating p, n, and e
Normally in an atom the number of electrons within the electron orbitals is equal to the number of protons in the nucleus.
The positive and negative charges cancel each other out. Therefore, the atom is said to be electrically neutral.
IMPORTANT
In all ATOMS the number of positively charged protons is always equal to the number of negatively charged electrons.

18. Calculating p, n, and e # protons = # electrons
Atomic number = # protons
Atomic mass = # protons + # neutrons
So, # Neutrons = Atomic mass - # protons
Or, # Protons = Atomic mass - # neutrons

19. Let’s practice…
Find how many neutrons are in iron if it has a mass of 55.
Mass = p + n and n = mass - p
Atomic # = protons = 26
55-26 = 29

20. Let’s practice… Find how many electrons are in an atom of magnesium.
Magnesium = Mg
Atomic # = 12 = protons
Protons = electrons in atoms
Mg has 12 electrons

21. QOD 9/20/12
How do you determine the amount of neutrons in an atom?

22. Isotopes
Isotopes of an element always have the same number of protons (atomic number), but they have a different number of neutrons
And therefore a different mass number
This is why mass values in the periodic table are decimals- the mass is the average of all naturally occurring isotopes

23. Isotopes
Example: Isotopes of carbon = C-12 has 6 p+ and 6 N0 but C-14 has 6 p+ and 8 NO
You should be able to find protons, electrons, and neutrons for an isotope, given its mass number

24. Isotopes Example: Find p, n, and e for hydrogen-3
The 3 at the end of the name indicates that the mass of this isotope is 3
Hydrogen atomic # is 1 (this will NEVER change
So p=1 and e=1
Mass = 3
n = mass-p= 3-1=2

25. Isotope Symbols atomic number 11
Show the mass number and atomic number
Give the symbol of the element
mass number
23 Na sodium-23
atomic number 11

26. Radioactivity
When an isotope has too many neutrons it makes the nuclei unstable
The nuclei breaks apart and shoots particles out
Alpha (Helium nuclei 2p + 2n)
Beta (electrons)
Gamma (photons, like light, but much smaller)
These particles can damage cells

27. Lewis Structures and Valence Electrons

28. Valence Electrons
Valence Electrons- the electrons on the outer orbital of an atom which may participate in chemical bonding.
All other electrons are known as inner-shell electrons
Each group in the periodic table has a specific number of valence electrons

29. Valence Electrons 1 8 3 4 5 6 7 2

30. Valence Electrons 1 8 6 How many valence electrons are in… Potassium?
Neon?
Oxygen? 1 8 6

31. Showing valence electrons
Lewis Structures
Showing valence electrons

32. Lewis Structure
A structure in which atomic symbols represent nuclei and inner-shell electrons, and dots are used to represent valence electrons.
Also called Lewis Dot Diagrams.

33. Drawing Lewis Structures
Draw the element symbol.
Ne Cl Be Si
Determine the number of Valence Electrons.
Ne= 8 (group 18)
Cl= 7 (group 17)
Be= 2 (group 2)
Si= 4 (group 14)

34. Add dots to the top, bottom, left and right of the element symbol until correct number of valence electrons is reached.
Draw a single dot on each side of the symbol first, then draw pairs to these dots.
In other words, do not pair electrons until each side of the symbol has one electron.
Ne Cl Be Si

35. The only exceptions… He Helium only has 2 valence
Write that on your periodic table!
Those 2 electrons DO PAIR UP He

36. Example As Draw the Lewis structure for Arsenic: Symbol = As
Valence Electrons = 5 As

37. Example
Draw the Lewis Structure for Bromine: Br

38. QOD 9/24/12
What part of the atom participates in bonding?

39. Chemical Bonding

40. Compounds and molecules
Most elements do not exist on their own
Atoms bond with other atoms to form compounds
A compound is 2 or more elements chemically bonded to each other
A molecule is 2 or more elements covalently bonded to each other

41. Compounds and molecules
Chemical formulas can be written for compounds
Examples of common compounds (they are also molecules):
Water = H2O (2 Hydrogen, 1 Oxygen)
Carbon Dioxide = CO2 (1 Carbon, 2 Oxygen)
Ammonia = NH3 (1 Nitrogen, 3 Hydrogen)
Table Salt = NaCl (1 Sodium, 1 Chlorine)

42. Subscript vs. Coefficient
A subscript is used when two or more atoms are bonded together to form a compound.
H2 =>means 2 Hydrogens Bonded together
A coefficient is used when one or more of a single compound or atom is needed.
2H2=> means 2 different H2 molecules are needed
(4 Hydrogen atoms total)
1 H2
2 H2 H H H H H H

43. Examples: List the number and types of atoms in the following compounds:
C6H12O6
6 carbons
12 Hydrogens
6 oxygens
H2O
2 hydrogens
1 oxygen
2H2O
4 hydrogens
2 oxygens
(C6H12O6)2
12 carbons
24 Hydrogens
12 oxygens
CO2
1 carbon
2 oxygen
4CO2
4 carbon
8 oxygen

44. How do compounds/molecules form?
Most atoms are not stable in their natural state, so they will bond with other atoms to make compounds
Individual atoms combine in a process called chemical bonding.
A chemical bond is an attractive force that holds atoms together

45. Why bond?
Elements are most stable when their valence shell has the maximum amount of electrons
Bonding of atoms depends on how many electrons they need to get a full shell.
Remember how to find valence electrons…

46. Valence Electrons 2 1 2 3 4 5 6 7 8

47. Chemical Bonding
Octet Rule- The tendency for atoms of elements to gain, lose, or share electrons so that their outer orbital (valence orbital) is full with eight electrons.
Hydrogen, helium, lithium and beryllium are exceptions, they are “happy” with just 2 electrons

48. Octet Rule
How many electrons will the following atoms need to fulfill the octet rule?
Calcium
Has 2, needs 6
Lithium
Has 1, needs 1
Tin
Has 4, needs 4
Xenon
Has 8, needs 0

49. Chemical Bonding
Atoms gain, share, or lose electrons to get 8 electrons in their outer shells
When they do this, they form bonds
There are 2 main types of bonds
Ionic Bonds
Covalent Bonds

50. Ionic Bonds

51. Remember… Protons are Positively charged (p+)
Electrons are Negatively charged (e-)
Electroneutrality means that an atom has equal number of positive and negative charges.
Same number of protons and electrons.

52. Ions
Atoms are electrically neutral, but they can gain or lose electrons to become ions.
Ion- an atom or group of atoms that has an electric charge because it has lost or gained electrons

53. Ionic Compound
The force of attraction between ions with positive and negative charges create an ionic bond.
Ionic bonding occurs between metals or metalloids and nonmetals.
Metals usually lose electrons and nonmetals gain electrons.

54. Turn to your periodic table and label
Nonmetal
Nonmetals
Metals
Metals

55. Covalent Bonding Occurs between nonmetal and nonmetal

56. Covalent Bond
A bond formed when two or more valence electrons are attracted by the positively charged nuclei of two atoms and are thus shared between both atoms.
Example: H2 (two hydrogens sharing their electrons)

57. Covalent Bond
Neither atom in a covalent bond has enough attraction to completely take an electron from the other atom (to become an ion); so the electrons are shared.
Because the atoms share electrons, covalent bonds are much stronger than ionic bonds.

58. Covalent Bonds
Lewis structures can be used to show how many covalent bonds an atom will form
Atoms can make 1 covalent bond for every UNPAIRED electron in their valence shell
So, Arsenic can make 3 bonds
This allows it to complete the octet rule since each bond results in a gain of one electron As

59. QOD 9/25/12
If I were an ion that had 6 valence electrons (remember, I want 8 to be happy), what would be easier…gaining 2 or losing 6?

60. Ions
To tell which ion an element will form…Think about the valence electrons…
3 or less VE, the atom will lose its electrons
5 or more, the atom will gain electrons to get to 8
If the atom has 4 or 8 valence electrons, then it will usually not form an ionic bond

61. Ions
The inner orbitals (besides valence) are full, so if the atom loses its current valence electrons, then it still achieves 8 valence electrons

62. Ions How do you know the charge of an ion?
If an ion GAINS electrons, the charge is Negative
If an ion LOSES electrons, the charge is Positive
Charges are written as SUPERSCIPTS
Fe 2+ or Sr 2-

63. Ions Examples: What is the charge of Calcium if it loses 2 electrons?
How many electrons has Fe 2+ lost? 2
What ion will Bromine form? 1-

64. Ionic Bond

65. Drawing Ionic Bonds Draw the Lewis dot structure:
Na (1 VE) Cl (7 VE)
Na + Cl

66. Drawing Ionic Bonds
Figure out which atoms lose and which atoms gain electrons.
Metal= lose and Nonmetal= gain; or
Each valence electron lost or gained uses energy, so for Sodium (Na) it would be more energy efficient to lose 1 electron rather than gaining 7!!
Na + Cl
Metal (loses) Nonmetal (gains)

67. Drawing Ionic Bonds Na Cl
Use arrows to indicate the movement of electrons from one atom to another.
Na Cl
Remember: Atoms need 8 electrons in their outer shell to be full. If there are 0 OR 8 electrons left on the Lewis structure, then its outer IS FULL

68. Drawing Ionic Bonds -1 +1 Cl Na
Draw the ions with the electrons moved and write their charges.
Sodium lost an electron
Chlorine gained an electron -1 +1 Cl Na

69. Chemical Formulas for Ionic Bonds
If the charges of the ions cancel out, then you can just write the element symbols together:
Na+1 + Cl-1 = NaCl

70. Chemical Formulas for Ionic Bonds
If they are not equal, then the superscript of one ion becomes the subscript of the other ion:
Ca +2 + Cl-1
= CaCl2
Notice that 1 is not written 2 1

71. More on Covalent Bonding

72. Covalent Bond
Atoms in covalent bonds can share 1, 2, or 3 pairs of electrons.
The more electrons shared, the stronger the bonds
1 pair = single bond
2 pairs = double bond
3 pairs = triple bond

73. Polar Covalent Bonds
Some covalent bonds can have slight charges depending on where the electrons are located.
Some atoms (usually bigger ones) attract the electrons more strongly than other atoms.
H2O for example is polar because the electrons tend to orbit more around the Oxygen atom than around the Hydrogen atom.

74. Drawing Covalent Bonds
Draw the Lewis Dot Structure for the atoms.
Cl H
Draw atoms as sharing electrons. Make sure all atoms have complete valence shells.
Cl H

75. Covalent VS Ionic Bonds
Review Chemical Bonds
Covalent VS Ionic Bonds
Nonmetals and
Nonmetals
Metals and Nonmetals

76. Chemical Reactions and Equations

77. Law of Conservation of Mass
The products of a chemical reaction have the same mass as the reactants.
Mass cannot be created nor can it be destroyed.
In a chemical reaction, the reactants (left of arrow) must have the same number and kinds of atoms as the products (right of arrow).

78. Law of Conservation of Mass

79. Chemical Reactions
Involve the rearrangement of atoms as reactants are converted to products.
The reactants and products have the same number and kind of atoms, they are just in a different arrangement.
In a chemical reaction, atoms do not become other kinds of atoms, nor do they appear or disappear.
Set of atoms in a particular arrangement
Set of atoms in a different arrangement

80. Chemical Equations
Chemical Equations are used to express the number and kinds of atoms in a chemical reaction.
The arrow means “reacts to form”
CH3CH2OH + 3O CO2 + 3H2O
2H2 + O H2O

81. Parts of a Chemical Equation
Subscript

82. Energy and Matter ALL chemical reactions involve energy
Energy is absorbed or released when chemical reactions occur
Activation energy is the amount of energy it takes for a reaction to occur.
Thousands of chemical reactions occur in an organism every day
Metabolism describes all of these chemical reactions (like digestion and oxygen absorption)

83. THE END

84. QOD 9/25/12
Take out chemical bonding 2 (keep on your desk)…pick up chemical bonding 1 on your way in
WEB ACTIVITY TO THE BASKET
Why am I making you draw bonds?