1. Chapter 3
Chemical Foundations

2. 3.1 The Elements
118 elements
92 occur naturally, the rest are synthesized
All matter in the universe can be chemically broken down into elements
Compounds are made by combining atoms of elements like words are formed from letters of the alphabet.
Words
Compounds

3. Abundance of Elements
9 elements make up about 98% of Earth

4. Elements of the human body: CHNOPS

5. The word element can have several meanings
Microscopic form
Single atom of that
element
Element
Macroscopic form
Sample of that
element large enough
to weigh on a balance
Element
Generic form
When we say the human body contains the element sodium or lithium, we do not mean that free elemental sodium or lithium is present. Rather we mean that atoms of these elements are present in some form.
Element

6. Name and Symbols for the elements
Each element has a unique name and symbol
Symbol usually consists of first one or two letters of elements name
Oxygen = O
Krypton = Kr
Sometimes the symbol is taken from the original Latin or Greek name

7. Formulas of Compounds
The types of atoms and the number of each type is shown using chemical symbols and subscripts.

8. Write the formula for each of the following, listing the elements in the order given
One atom of sulfur and three atoms of oxygen
Two atoms of nitrogen and five atoms of oxygen

9. give the number of each atom in the following:
Ca(NO3)2
AlPO4
Al2(SO4)3
2H2O

10. 3.2 Early Ideas about matter
Greek philosophers – formed explanations based on life experiences
Proposed four ‘elements’

11. Democritus – 400 BC
Believed matter was made of tiny particles called atomos
Cannot be created, destroyed, or divided
Aristotle disagreed

12. Alchemy Origin of the word Chemistry
Tried to make gold out of abundant elements
Invented many of the techniques still used today like filtration and distillation

13. antoine lavoisier
French scientist known as the “Father of Chemistry”
Made Chemistry quantitative by taking accurate measurements
Wrote 1st chemistry textbook
Beheaded in 1794 for being funded by taxes

14. Proust (1754-1826) Proposed the Law of Constant Composition (1794):
A given compound always contains the same proportion by mass of the elements of which it is composed.

15. John Dalton (1803) Revived and Revised Democritus’ idea
Came up with his own Atomic Theory
All elements are composed of tiny particles called atoms which cannot be broken into smaller parts.
All atoms of the same element are identical, atoms of different elements are different

16. Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms
Chemical reactions take place when atoms rearrange. Atoms are not created or destroyed during chemical reactions.

17. 3.3 Defining the Atom
The smallest particle of an element that retains the properties of the element
Atoms are very small
One Cu atom = 1.28 x m
Solid copper penny = 2.9 x atoms
If 1 atom = size of an orange, an orange would be as big as the earth!

18. Scanning tunneling microscope (STM) allows individual atoms to be seen
Scans across the surface of atoms
silicon

19. J.J. Thomson – 1897
Worked with a cathode ray tube

20. Discovered cathode ray was attracted to positively charged plate

21. What 2 things did Thomson learn from this experiment?

22. By measuring the effects of both magnetic and electric fields on a cathode ray, Thomson determined the mass of the charged particle is less than the hydrogen atom (the lightest atom known)
Why is this significant?

23. What subatomic particle did Thomson discover?

24. Thomson’s model
Matter is neutral so some positive charge needs to balance out the negative electrons
Plum pudding model

25. Ernest Rutherford

26. In 1911, Rutherford and his coworkers at the University of Manchester, England, directed a narrow beam of alpha particles at a very thin sheet of gold foil.
Based on Thomson’s model of the atom he expected the alpha particles to pass through the foil but not all did!

28. What conclusion can Rutherford draw from this result?

29. Rutherford concluded:
Atom consists of mostly empty space
If an atom had a diameter of 2 football fields the nucleus would be the size of a nickel
Almost all + charge & mass are found in nucleus

30. Rutherford Model of the atom

31. Atomic Structure
Ernest Rutherford showed that atoms have internal structure.
The nucleus, which is at the center of the atom, contains protons (positively charged) and neutrons (uncharged).
Electrons move around the nucleus.

32. James Chadwick - 1932 What we knew
Electrons & Protons have opposite charges
Neutral atom has same number of electrons as protons
Mass of atom was too much to just be made of protons & electrons

33. Showed nucleus contained a particle with the same mass as a proton but no charge – neutron

34. Particle
Symbol
Location
Charge
Mass
Electron
Proton
Neutron

35. The number of protons in an atom identifies it as a particular element
Number of protons = atomic number
Periodic table is organized in order of increasing atomic number

36. All atoms are electrically neutral therefore
# of protons =

37. Determine the number of protons and electrons in an atom of Molybdenum

38. Mass Number Mass number = protons + neutrons Neutrons =
Mass numbers are given in atomic mass units (amu)
1 amu = 1/12 mass of Carbon-12 atom

39. Be Atomic Shorthand • Beryllium- - -atomic number 4 mass number 9
The atomic number is written as a subscript.
The mass number is written as a superscript. Be

40. Element
Atomic Number
Protons
Electrons
Neutrons
Mass number 19 20 35 80 10

41. Isotopes
Atoms with the same number of protons but different number of neutrons

42. Most naturally occurring elements have two or more stable isotopes
One is usually more common than the others
Oxygen – 16, oxygen – 17, oxygen - 18

43. mass number vs. atomic mass
Mass number = protons + neutrons
Atomic mass (on periodic table) = weighted average of all the isotopes of an element

44. Calculating atomic mass

45. Unknown element X has two isotopes. 6X has an atomic mass of 6
Unknown element X has two isotopes. 6X has an atomic mass of amu and a 7.59 % abundance. 7X has an atomic mass of amu and a 92.41% abundance. What is the atomic mass of the unknown element? What is the identity of the unknown element?

46. Ions Atoms can form ions by gaining or losing electrons.
Metals tend to lose one or more electrons to form positive ions called cations.
Cations are generally named by using the name of the parent atom.

47. Ions
Nonmetals tend to gain one or more electrons to form negative ions called anions.
Anions are named by using the root of the atom name followed by the suffix –ide.

48. O2- Al3+ 19 18 146C Element Protons Mass number Atomic # Electrons
Neutrons
Mass number
O2-
Al3+ 19 18
146C
Potassium - 41

49. Ion charges can be predicted from the periodic table

50. What can change in an atom?
Protons – NEVER!!!
Neutrons – if changed an isotope is formed
Electrons – if changed an ion is formed

51. Proton Changed Whole new atom!!!
Oxygen loses a proton it becomes Nitrogen
Oxygen gains a proton it becomes Fluorine

52. Neutron Changed Different version of the same atom is formed (isotope)
Oxygen – 16 has 8 Neutrons
Oxygen – 17 has 9 Neutrons
Oxygen – 18 has 10 Neutrons

53. Electrons Changed Charged version of the same atom is formed (ion)
Oxygen gains 2 electrons – 10 electrons & 8 protons
Anion
Oxygen loses 2 electrons – 6 electrons & 8 protons
Cation

54. Compounds That Contain Ions
Ions combine to form ionic compounds.
Properties of ionic compounds
High melting points
Conduct electricity
If melted
If dissolved in water

55. Ionic compounds are electrically neutral
Total positive charge must cancel out total negative charge

56. Formulas for ionic compounds
Write cation symbol followed by anion symbol
The number of cations and ions must be correct so their charge sums to zero

57. Write the formula for compounds containing the following ions:
Potassium and oxygen
Calcium and sulfur
Magnesium and nitrogen

58. 3.4 Introduction to the periodic Table
In 1913 our current periodic table was developed by Henry Moseley who arranged the atoms by atomic number
Periodic law – when elements are arranged according to increasing atomic number, there is a periodic repetition of chemical and physical properties

59. The Modern Periodic Table
Columns = groups
Numbered 1 – 18
Correspond to the number of outermost electrons
Have similar properties
Some have special names
Rows = periods
Numbered 1 – 7
Correspond to outermost energy level

60. Physical States and Classes of Elements
Most elements are solid at room temperature
Br & Hg are liquid
N, O, F, Cl, and Noble gases are gas

61. Metals Shiny Solid at room temperature
Good conductors of heat & electricity
Malleable
Ductile
Found to the left of the staircase
1 exception =

62. Alkali metals – group 1 elements
Except for
Very reactive
# of valence electrons =

63. Alkaline earth metals – group 2 elements
Also highly reactive
# of valence electrons =

64. Transition metals – group 3 – 12 (d block)
Number of valence electrons varies

65. Inner transition metals – f block
Number of valence electrons varies
Lanthanide & actinide series

66. Nonmetals Gasses or dull looking solids
1 exception =
Poor conductors of heat and electricity
Found to the right of the staircase

67. Halogens – group 17
Highly reactive
# of valence electrons =

68. Nobel gases – group 18
Extremely unreactive
# of valence electrons =

70. Metalloids Border the staircase
Have properties of both metals and nonmetals
Semi-conductors = conduct electricity only under certain conditions

72. Natural States of the Elements
Most elements are very reactive.
Elements are not generally found in uncombined form.
Exceptions are:
Noble metals – gold, platinum and silver
Noble gases – Group 8

73. Natural States of the Elements
Diatomic Molecules
Nitrogen gas contains
N2 molecules.
Oxygen gas contains
O2 molecules.

74. Natural States of the Elements
Diatomic Molecules

75. Natural States of the Elements
Elemental Solids
Carbon
atoms
Diamond
Graphite
Buckminsterfullerene