1. The Atom

2. Subatomic Particles
A. Atomic Number
B. Mass Number and Isotopes
C. Electrons and Ions
D. Nuclear and Hyphenation Notation
E. Average Atomic Mass
Weighing and Counting Atoms
A. Mole Atoms
B. Mole Mass
C. Mass Atoms

3. Subatomic Particles A. Comparing Particles
Relative
mass
Actual
mass (g)
Name
Symbol
Charge
Electron e- -1
9.11 x 10-28
Proton p+ +1
1amu
1.67 x 10-24
Neutron n0
1amu
1.67 x 10-24

4. Subatomic Particles B. Atomic Number and Mass Number
1. the number of protons in the nucleus of an atom
a. identifies the element
b. no two elements have the same atomic number
Ex. C is 6, N is 7 and O is 8
carbon nitrogen oxygen

5. Subatomic Particles B. Atomic Number and Mass Number
a. the number of protons plus neutrons in the nucleus of an atom
b. mass number is very close to the mass of an atom in amu (atomic mass units)
c. two atoms with the same atomic number but different mass number are called isotopes
1) (mass #) – (atomic #) = #n 0

6. X Subatomic Particles C. Nuclear Notation
Nuclear Notation is one method for depicting isotopes of an element
contains the symbol of the element, the mass number, and the atomic number
Mass number X
Atomic number

7. Na 23 11 Subatomic Particles C. Nuclear Notation How many protons?
How many neutrons?
How many electrons? 23 Na 11

9. Subatomic Particles C. Hyphen Notation
1. Element symbol or name – mass #
2. EXAMPLES
a. Fluorine-19
b. C-14
c. U-238

10. Subatomic Particles D. Ions
1. Electrons and Ions
a. For neutral atoms, #e- = #p+
b. If there are more electrons, a negative ion
forms (anion)
c. If there are less electrons, a positive ion
forms (cation)
For now, we will work only with neutral atoms

11. The modern table Elements are still grouped by properties.
Similar properties are in the same column.
Order is in increasing atomic number.
Added a column of elements Mendeleev didn’t know about.
The noble gases weren’t found because they didn’t react with anything.

12. Trend of periodic table
group1
group2
group13
group14
group15
group16
group17
group18 H He Li Be B C N O F Ne Na Mg Al Si P S Cl
Ar - K Ca
Boiling point:
group1
group2
group13
group14
group15
group16
group17
group18
21K 4K
1600K
2780K
2800K
4620K
77K
90K
85K
27K
1162K
1390K
2600K
2950K
553K
718K
239K
87K
1030K
1760K

13. Melting Point
group1
group2
group13
group14
group15
group16
group17
group18
14K 0K
453K
1560K
2348K
3823K
63K
54K
53K
24K
379K
923K
933K
1687K
317K
388K
171K
83K
336K
1115K

14. Horizontal rows are called periods
There are 7 periods

15. The elements in the A groups are called the representative elements

16. The group B are called the transition elements
These are called the inner transition elements and they belong here

17. Group 1A are the alkali metals
Group 2A are the alkaline earth metals

18. Group 7A is called the Halogens
Group 8A are the noble gases

19. Subatomic Particles D. Formation of Ions
Examples of Ions
Atom loses electrons Atom gain electrons
and form cations and forms anions
Cations (+ ions) Anions (- ions)
K+ Br-
Ca O2-
Al N3-

20. ions

21. D. Formation of Ions From Atoms
Na loses an electron
and forms a cation
Na – e- --> Na+
Cl gains an electron
and forms an anion
Cl + e- --> Cl-

23. Subatomic Particles D. Changing Number of Particles
1. You can never change the number of
protons and have the same element
2. If you change the number of neutrons in an atom, you get an isotope
3. If you change the number of electrons in an atom, you get an ion

24. Mass of Atoms A. Atomic Mass
1. Mass of an atom
a. too small to measure in grams
b. use relative mass (amu)
1) atomic mass unit
2) 1 amu is defined as 1/12 the mass
of one C-12 atom

25. IV. Mass of Atoms B. Average Atomic Mass
1. weighted average mass of all known isotopes
a. weighted means that the frequency of an isotope is considered
b. mass of each isotope is multiplied by
its percent occurrence in nature – then
masses of all isotopes is added to get
the average atomic mass

26. IV. Mass of Atoms C. The Mole and Molar Mass
1. measures the amount of substance
a. 1 mole = 6.02x1023 (Avogdro’s #) of
particles (atoms, molecules, ions, electrons)
b. standard – 1mole is the number of atoms in
12g of C-12 isotope
2. Molar mass – mass in grams of one mole
(mol) of any substance
a. numerically equal to atomic mass in amu
b. unit is grams/mol

27. What is average atomic mass?
Average atomic mass is the weighted average of the atomic masses of the naturally occurring isotopes of an element

28. Calculating a Weighted Average
Example
A box contains two size of marbles. If
25.0% have masses of 2.00 g and 75.0%
have masses of 3.00 g what is the weighted
average?
(.250) (2.00) + (.750) (3.00) = =
2.75g

29. Calculating Average Atomic Mass
EXAMPLE
Boron has two isotopes:
B-10 (mass amu) 19.8% abundance
B-11 (mass amu) 80.2% abundance
Calculate the average atomic mass.
(.198) (10.013) + (.802) ( ) =
1.98 amu amu = amu

30. Calculating Average Atomic Mass
Calculate the average atomic mass of Mg.
Isotope amu (78.99%)
Isotope amu (10.00%)
Isotope 3 – amu (11.01%)
(23.985)(.7899)+(24.986)(.1000)+(25.982)(.1101)
18.95 amu amu amu = amu

31. Average Atomic Mass
Helium has two naturally occurring isotopes, He-3 and He-4. The atomic mass of helium is amu. Which isotope is more abundant in nature?
He-4 is more abundant in nature because the atomic mass is closer to the mass of He-4 than to the mass of He-3.

32. Calculating Average Atomic Mass
Process
Multiply %occurrence x mass of isotope
Add products for each isotope
isotope occurrence isotope occurrence
Ex. X- 40 (30.0% ) X-30 (70.0%)
(40 x .300) + (30 x .700) =
= 33 amu

33. Isotopic Pennies – number of pre and post 1982
a. Let X be the number of pre-1982 pennies
b. Let 10-X be the number of post-1982 pennies
c. (X)(3.1g) + (10-X)(2.5g) = mass of 10 pennies
pre post-82
EXAMPLE (Mass of a sample of pennies is 31.0g)
(X)(3.1g) + [(10-X)(2.5g)] = 31.0 g
3.1X X = 31.0g
.6X + 25 = 31.0g
.6X = 6.0g X = 6.0g/.6
X = 10 pre-82 pennies
10-X = 0 post-82 pennies

34. Isotopic Penny Lab- Average Atomic Mass
Calculate percent of pre-82 and post-82 pennies
# of pre-82 pennies x 100% # post-82 pennies x 100%
Calculate the average atomic mass of coinium
(% pre-82)(3.1g) + (% post-82)(2.5) = average atomic mass

35. The Mole What is a mole in chemistry?
What conversion factors are associated with the mole?
Types of conversions involving mole equalities

36. What is a Mole? What are mole equalities
A mole is equal to 6.02 x particles
Particles can be atoms, molecules or ions
6.02 x 1023 is Avogadro's Number
Mole Equalities
- 1 mole = molar mass
- 1 mole = x 1023 particles

37. Mole Conversions [mass-mole-atoms] Type Equality Used
1. MOLES  MASS
2. MASS  MOLES mole= molar mass (g)
3. MOLES  ATOMS
4. ATOMS  MOLES 1 mole = 6.02 x 1023 atoms
5. MASS  ATOMS 1 mole = 6.02 x 1023 atoms
6. ATOMS MASS mole = molar mass (g)

38. Mole Calculations Using Conversion Factors
1 mole molar mass
6.02 x mole
PARTICLES <----> MOLES <----> MASS
6.02 x mole
1 mole molar mass

39. Solving Mole Problems EXAMPLES 1.00 mole of He = 4.00 g.
2.00 mol He X 4.00g He =
mole He
8.00 g He

40. EXAMPLES 1.00 mole He = 6.02 X 1023 atoms
2.00 mole He = ________atoms He
2.00 mole He x x 1023 atoms He = x 1023
mole He
1.20 x 1024 atoms He
16.00g He = _____ moles He
16.0 g He x 1 mole He =
g He moles He

41. EXAMPLES 3.01 X 1023 atoms He = _____ moles
3.01 x 1023 atoms He x mole He =
x 1023 atoms He
.500 mol He
8.00g He =______atoms He
8.00 g He x 1 mole He x x 1023 atoms He =
g He mole He
12.04 x 1023 atoms He = 1.20 x 1024 atoms He

42. Sample Problems Moles to mass. Find the mass of 3.50 moles of carbon.
Mass to Moles
How many moles of carbon are contained in
60.0 g of carbon?
Moles to Atoms
How many atoms of carbon are found in 4.00 moles of carbon?

43. Sample Problems Atoms to Moles
How many moles of carbon are represented by
1.806 x 1024 atoms of carbon?
Mass to Atoms
How many carbon atoms are found in 36.0g of
carbon?
Atoms to Mass
What is the mass of x 1024 atoms of carbon?

44. More Sample Problems 2.00 moles of Cu = atoms of Cu
60.0 grams of C = moles of C
3.00 x 1023 atoms He = moles of He
2.50 moles Al = grams of Al
28.0 grams N = atoms of N
1.80 x 1023 atoms Mg = grams of Mg

45. Mole Calculations (Mass of Helium is 4.00 )
mole of helium = 4.00g
2.00 mole of helium = 8.00g
1.00 mole of helium = 6.02 x 1023 atoms
2.00 mole of helium = 1.20 x 1024 atoms
16.0g of helium = 4.00 mol
3.0l x 1023 atoms of helium = .500 moles
8.00g of helium = x 1024 atoms.