1. Chapter 5: Atomic structure & the Periodic Table
College Prep Chemistry

2. Section 5.1 – The Atom
Atoms: the smallest particle of an element that retains the properties of that element.
(Greek: atomos = indivisible)
Democritus (Greek teacher in the 4th century)
First suggested that atoms existed

3. The Atom
1700’s – chemists were able to relate changes to individual atoms
Average atom size:
Mass = 1 x 10 –23 g
Diameter = 1 x 10-8 cm
How small is that?100,000,000 copper atoms in a row would = 1 cm in length!

4. John Dalton’s Atomic Theory
1. All elements are composed of tiny indivisible particles called atoms.
2. Atoms of the same element are identical. The atoms of any one element are different from those of any other element.

5. Atomic Theory (cont’d)
3. Atoms of different elements can combine with one another in simple whole number ratios to form compounds.
H2O C12H22O NOT H2.5O¾
4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element are not changed into atoms of another!

6. Atomic Theory (cont’d)
5. Atoms can not be infinitely subdivided.

7. Just how small is an atom?
100,000,000 copper atoms in a row would = 1 cm in length!

8. Section 5.2 – Structure of the Nuclear Atom
Most of Dalton’s Atomic Theory is accepted
One revision includes that idea that atoms are indivisible….
There are 3 parts to an atom….
1. electrons
2. protons
3. neutrons

9. Electrons (e-) Negatively charged subatomic particles
J.J. Thomson discovered in 1897
Passed a electric current through gases called a “Cathode Ray”
Opposites attract and the electrons were attracted to the positive ends and lights up!

10. Electrons (cont’d)
How televisions work!

11. 2. Protons (p+) Positively charged particles
1,840 times heavier then an electron

12. 3. Neutrons (no) Subatomic particles with no charge
Discovered by Sir James Chadwick
Mass is nearly the same as a proton

13. Summary of Subatomic Particles
Symbol
Relative Charge
Approx. Relative Mass (amu)
Actual Mass (g)
Electron e- 1-
1/1840
9.11x10-28
Proton p+ 1+ 1
1.62x10-24
neutron no

14. Atomic Nucleus Discovered by Ernest Rutherford (1911)
Gold Foil Experiment

15. Gold Foil Experiment

16. Atomic Nucleus- Rutherford’s Model
The alpha particles were positively charged - Like things repel
Therefore – there must be a densely, positively charged center
Nucleus – has a positive
center
- with an electron cloud

17. Atomic Nucleus: Bohr’s Model
Niehls Bohr
Atom has a nucleus but electrons orbit in definite energy levels

18. Section 5.3 – Distinguishing Between Atoms
Atomic Number - the number of protons in the nucleus of an atom of an element
Atoms are electrically neutral
Tells how many electrons there are also!
Periodic Table
#1 – Hydrogen:
has 1 p+ and 1 e-
#6 – Carbon:
has 6 p+ and 6 e-

19. On the Periodic Table
Mass Number – total number of protons and neutrons in a nucleus
# of neutrons = mass # atomic #
= (# p+ + # no) - (# p+)
Beryllium – 9
The number “9” is the mass number
# of p+? # of no? # of e-?

20. Determining Mass Number:
# of protons = atomic number
# of electrons = # of protons (in a neutral atom)
# neutrons = Mass # - Atomic #

21. Atomic Notation:

22. Ions: Atoms with a charge (results from gain/loss of electron)
If an atom GAINS an electron = ANION
Negative charge
Ex: Cl-
If an atom LOSES an electron = CATION
Positive charge
Ex: Ca2+

23. Isotopes
Definition – atoms that have the same number of protons but different numbers of neutrons
Different types of the same element
Ex) Carbon – has 3 isotopes
1) Carbon – 12
2) Carbon – 13
3) Carbon – 14
Differ by # of no

24. Isotopes of Carbon All have the same # of p+ 1) Carbon – 12
If not, it would be a different element
All have 6 protons
1) Carbon – 12
Has 6 neutrons
2) Carbon – 13
Has 7 neutrons
3) Carbon – 14
Has 8 neutrons

25. Isotopes of Hydrogen Hydrogen-1: 1 p+ and 0 no
Relative abundance = %
Commonly called normal “hydrogen”
Hydrogen-2: 1 p+ and 1 no
Relative abundance = 0.015%
Commonly called heavy hydrogen or “deuterium”
Hydrogen-3: 1 p+ and 2 no
Relative abundance = ~0.00%
Commonly called “tritium”

26. Atomic Mass
Definition – weighted average mass of the atoms in a naturally occurring sample of the element
Carbon-12 = % abundant
Carbon-13 = 1.11% abundant
Carbon-14 = ~ % abundant

27. Atomic Mass Formula: Formula: Atomic = relative mass relative mass
mass abund. x # abund. x # +
Repeats for however many isotopes exist for that element….

28. Atomic Mass Sample Problem:
Chlorine has 2 isotopes: chlorine-35 which is 75.77% abundant and chlorine-37 which is 24.33% abundant. What is the atomic mass of chlorine?

29. Atomic Mass 35 Cl = 75.77% abundant 37 Cl = 24.33% abundant
= (35 amu x ) + (37 amu x )
= ( amu) ( amu)
= amu
Compare to value on Periodic Table = amu which rounds to 35.5 amu

30. Section 5.4 – The Periodic Table: Organizing the Elements
Dmitri Mendeleev ( ) – first person to organize the elements in a chart
Organized about 70 elements by increasing atomic mass
Left blank spaces for elements which were not discovered yet

31. Mendeleev’s Periodic Table

32. Arranged by increasing atomic number instead!
Periodic Table
Henry Moseley (1913) – rearranged Mendeleev’s periodic table to the current configuration
Arranged by increasing atomic number instead!
Also grouped elements by their properties

33. Moseley's Periodic Table
What is the mass of potassium and argon?
#19 Potassium = amu
#18 Argon = amu
If Mendeleev’s Periodic Table was our arrangement, the gas Argon would be lined up with the metals!

34. Modern Periodic Table Arrangement:
Groups/Families = columns
Periods = rows
Periodic Law: when the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

35. Periodic Table

36. Parts of the Periodic Table
Line of Demarcation: jagged “stairs” which separate the left and right side
Metals = left and below the line of demarcation
Nonmetals = right and above the line of demarcation
Metalloids = elements along the line

37. Parts of the Periodic Table
Metals
Conduct electricity & heat
Malleable
Strong
High melting and freezing points
Mostly solids
Have Luster

38. Parts of the Periodic Table
Nonmetals
Insulators – do not conduct well
Brittle
Low melting and freezing points
Contain gases and liquids
Are dull

39. Parts of the Periodic Table
Metalloids – have properties of both metals and nonmetals
Ex) Silicon
-semi-conductor
-brittle

40. Groups of the Periodic Table
Group 1 = Alkali Metals
Violently react with water

41. Groups of the Periodic Table
Group 2 = Alkali Earth Metals
Very common in the earth’s surface
Ex)
Beryllium
Magnesium
Calcium
Strontium
Barium
Radium

42. Groups of the Periodic Table
Group 3-12 = Transition Metals
Most of the common metals
Lanthanide & Actinide Series = Inner Transition Metals

43. Groups of the Periodic Table
Group 13-16: Either metals, metalloids, or nonmetal
Depends on their side of the line
Group 17: Halogens
Highly reactive
Fluorine
Chlorine
Bromine
Iodine

44. Groups of the Periodic Table
Group 18: Noble Gases
All gases
Do not react or combine with any other element

45. Chapter 5 Review Problems
Page: 129 #33, 36, 38-43, 45-46, 48-49, 53, 57