1. Chapter Two Atoms & The Periodic Table

2. Section 2.1 Atoms First

3. Atoms
Atoms are the smallest quantities of matter that still retain the property of that matter

4. A brief history
Democritus was the first to develop this idea of an atom in the 5th century
John Dalton was the first to formalize the idea of an atom with Dalton’s atomic theory
Known as the “father of atomic theory”
The word “atom” comes from the Greek word “atomos” meaning “uncuttable.”

5. Dalton’s Atomic Theory
All matter is made up of atoms
Atoms are indivisible
Atoms of the same element are identical
Atoms of one element are different than atoms of another element
Atoms come together to form compounds

6. Dalton’s Law of Multiple Proportions
If two elements can combine to create multiple compounds, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers
CO CO2
100 g of C g of C
133 g of O g of O

7. Section 2.2 Subatomic Particles & Atomic Structure

8. Subatomic Particles & Their Discovery
Who Discovered It
How was it Discovered
Electron (and Charge-to-Mass ratio)
J.J. Thomson
Cathode Ray Tube (Cathode Ray Experiment)
Charge of the Electron
Robert Millikan
Oil Drop Experiment
Proton & Nucleus
Ernest Rutherford
Gold Foil Experiment
Neutron
James Chadwick
Beryllium Bombardment

9. Comparing All 3 subatomic Particles
Charge
Location
Contribution to Atom
Proton +1
In the nucleus
Mass
Neutron
Electron -1
Outside nucleus
Volume

10. Section 2.3 Atomic Number, Mass Number and Isotopes

11. Element Symbols

12. Isotopes Not all atoms of a given element are identical
Most elements have 2 or more isotopes (atoms with same # of protons, different # of neutrons)

13. Isotopes Isotopes behave like each other Named after their mass number
Ex: U-235 (“Uranium two thirty five”)
If mass number is not given, use rounded atomic mass from PT.
If mass number is given (or if protons & neutrons are given), use that value instead of on the PT.
If mass # is different than what’s on PT, it is an isotope

14. Ions Atoms with charges (different # of electrons)
Positive ions called cations
Negative ions called anions

15. Let’s Do Some Structural Practice!

16. Fill Out the Table Below
# of Protons
# of Neutrons
# of Electrons
Mass Number
Atomic Number
Ion?
Isotope? 14 18 20 6 13 10 29

17. Practice
List the number of protons, neutrons, and electrons in the following elements:
Carbon-14 Iodine-128
An atom has a mass number of 114 and 66 neutrons. Write the isotope notation for this atom.

18. Section 2.4 Average Atomic Mass

19. Average Atomic Mass Mass of an atom in atomic mass units (a.m.u)
Based off of 1/12 of a carbon atom
Most elements are mix of isotopes in nature
Average Atomic Mass is reported

20. Practice
The atomic masses of two stable isotopes of copper, copper-63 and copper 65, are and amu, respectively. If copper-63 is 69.17% and copper-65 is 30.83%, what is the average atomic mass of copper?

21. One More
The atomic masses of 34Cl and 35Cl are amu and amu, respectively. Calculate the natural abundance of these two isotopes. The average atomic mass of Cl is amu.

22. Section 2.5 The Periodic Table

23. The Periodic Table Mostly metals (left of stair step)
Good conductors of heat/electricity
Non metals (right of stair step)
Poor conductors of heat/electricity
Metalloids/Semi-metals (on stair step)
Properties of both metal and nonmetal
B, Si, Ge, As, Sb, Te, Po, At

24. The Periodic Table

25. The Periodic Table Groups: vertical columns Periods: horizontal rows
Elements in the same group share similar chemical properties
18 groups
Periods: horizontal rows
Elements transition from metal to nonmetal across a period

26. The Periodic Table

27. Section 2.6 The Mole and Molar Mass

28. The Mole A unit of quantity (how much)
Mole = mol
1 mole = x 1023 “particles”
“particles” can be atoms, molecules, or formula units
This number is called Avogadro’s Number

29. Molar Mass
Molar Mass = the mass of ONE MOLE of a substance
g/mol

30. Molar Mass 1 mole of water = 18.02 grams
1 mole sodium chloride = g
1 mole helium gas = g

31. Molar Mass Molar mass is found by Listing elements in compound
Determining their mass found on periodic table
Multiplying by how many atoms there are
Adding these values
Ex: H2SO4

32. A helpful guide

33. Conversions
How many molecules of magnesium chloride (MgCl2) are there in grams of magnesium chloride?
How many chlorine atoms are there in the same mass of magnesium chloride?

34. Group Quiz
1)Write the appropriate isotope notation for the following: Z=29, A=64 2)How many protons, neutrons, & electrons in 3)Rb-85(72.17%) is If the average atomic mass of Rb is , what is the atomic mass of Rb-87(27.83%). 4)How many grams is 5.30 x 1023 molecules of K2O? +3