1. instructions? 1. Dalton wrote which theory?
Review
Answer the following quest. on the blank sheet of paper.
1. Dalton wrote which theory?
2. List the 3 subatomic particles.
3. Which two subatomic particles make-up the nucleus?
4. A negatively charged particle is called an ___________.
5. Draw a circle on your paper, inside the circle draw the nucleus, e-, p+ and n0 for the atom Carbon.
instructions?

2. 6. Most of the mass of an atom is found where?
Warm-up
Directions: # paper 6-10, write just the answer
6. Most of the mass of an atom is found where?
7. Whose theory states that all atoms of the same element are identical?
8. Which experiment led to the discovery of the nucleus?
9. What is the charge on the nucleus? What cancels out this charge?
10. A cathode ray proved the presence of an _____ & a canal ray showed ___ were present in an atom. What piece of equipment was used?

3. Distinguishing between atoms & atoms of an element.
Atomic Structure
and Isotopes
Distinguishing between atoms & atoms of an element.

4. Protons, Neutrons and Electrons
I. Subatomic particles
The atom contains 3 subatomic particles:
Protons, Neutrons and Electrons
A. Elements are different from one another due to their number of protons.
Atomic # = # of protons
1. The # of protons:
Identifies an element
Increases left to right across each row
How many p+ are in Boron?

5. B. Atoms are electrically neutral.
# of protons = # of electrons
1. The # of electrons:
Determines the chemical reactivity of the element
How many e- are in Boron?
2. If an atom:
Gains or loses electrons it is called an ION!
Why would an atom gain or lose e- ?
To become stable.

6. Mass # = Protons + Neutrons
C. The mass of an atom is concentrated in the atoms nucleus.
Mass # = Protons + Neutrons
D. The mass # is:
A whole #.
Why are electrons NOT included in the calculation for mass #?
Electron mass is negligible compared to protons.
What is the mass # for C?

7. How many neutrons are there in an atom of Ag? 61 neutrons
E. Calculating the # of neutrons
Neutrons = Mass # - Atomic #
How many neutrons are there in an atom of Ag?
108
- 47 =
61 neutrons
Electron mass is negligible compared to protons.

8. Element  Ag Cl - 35 How many n0 are in Cu? 64 – 29 = 35
Mass #
108 47
Atomic #
How many n0 are in Cu?
64 – 29 = 35
Write the atom, Chlorine, in the form of “symbol of element-mass #”.
Electron mass is negligible compared to protons.
Cl - 35

9. Review: Review Atomic # = # of protons # of protons = # of electrons
Mass # =
Protons + Neutrons
Electron mass is negligible compared to protons.
Mass # - Atomic #
Neutrons =
Review

10. Lecture notes K Be 4 5 4 Ne 10 10 10 19 20 19 Element Protons Neutrons
Electrons 9 4 20 10 K Be 4 5 4 Ne 10 10 10 19 20 19

11. II. Average Atomic mass or amu
A. The amu is the sum of protons & neutrons in the nucleus and the relative abundance of isotopes.
Average Atomic mass is a decimal #. 11
Atomic Number Na
Sodium
Because the protons and neutrons are whole numbers but the isotope is the relative abundance in nature a percent or average abundance. The relative atomic mass of an element is the average mass of all the isotopes present compared to 1/12th of the mass of carbon-12 atom (12C = ie the standard).
Amu
22.99
The mass # would be 23 g, doesn’t include isotopes.

12. Important Information:
1. The average atomic mass of an element is usually closest to the isotope with the highest natural abundance.
2. Elements with an average atomic mass close to a whole number exist predominantly in nature as one natural isotope.
3. In nature most elements occur as 2 or more isotopes.

13. Examples:
Which isotope of Cu is more abundant: Cu-63 or Cu-65 (atomic mass of Cu is amu)?
Boron has 2 isotopes: B-10 and B-11. Which is more abundant, given that the atomic mass of boron is 10.81?
Cu-63, B-11, 28- most abundant, 29-2nd, 30-last
There are 3 isotopes of Si; they have a mass # of 30, 29, & 28. The atomic mass of Si is amu. Which is the most abundant, 2nd abundant and least.

14. YES III. Isotopes A. What is an isotope?
An atom of an element that has a different number of neutrons while the protons and electrons remain the same.
B. Are isotopes of an element chemically the same?
YES
Neutrons only change the mass, e- and p+ stay the same.

15. C. How do isotopes of the same element differ?
1. different number of neutrons.
2. Only the mass changes!
D. Write the formula for the following isotopes of chlorine, Cl-35 & Cl-37. 35 37 Cl Cl 17 17
18 neutrons
20 neutrons
Determine the # of neutrons in each isotope of chlorine.

16. IV. How is the average atomic mass unit defined?
A. The unit is based on a reference isotope or standard, carbon-12 isotope, that has a mass of exactly 12 amu.
1. The mass of a single p+ or n0 is ~1 amu.
A carbon-12 atom has six protons and six neutrons in its nucleus and its mass is set at 12 amu. The protons and neutrons account for nearly all of its mass. Therefore, the mass of a single proton or neutron is 1/12 of 12 amu, or about 1 amu.

17. X How is the average atomic mass of an element determined? Formula:
% abundance of isotope in decimal form
Mass of the isotope X
A carbon-12 atom has six protons and six neutrons in its nucleus and its mass is set at 12 amu. The protons and neutrons account for nearly all of its mass. Therefore, the mass of a single proton or neutron is 1/12 of 12 amu, or about 1 amu.
The sum of the individual isotope mass contributions will equal the atomic mass.

18. X X = = X + = Examples: Formula: .754 26 amu Cl – 35 = 35 amu 9.1 amu
% abundance of isotope in decimal form
Mass of the isotope X
Formula:
Determine the atomic mass of chlorine given two known isotopes, Cl-35 & Cl-37. The relative abundances are 75.4% & 24.6%. X
.754 =
26 amu
Cl – 35 =
35 amu
Do the example on worksheet A =
9.1 amu
Cl – 37 = X
37 amu
.246 + =
26 amu
9.1 amu
35.1 amu
35 amu

19. Instructions Convert 3.94 inches/hr to meters/sec Convert 54 nL to uL
Take out your calculator & laminated periodic table
Take out your atom/isotope lecture notes and a blank sheet of paper.
Warm Up:
Convert 3.94 inches/hr to meters/sec
Convert 54 nL to uL
Instructions

20. X X = = X + = Examples: Formula: .989 12 amu C – 12 = 12 amu .14 amu
% abundance of isotope expressed as a decimal
Mass of the isotope X
Formula:
Determine the atomic mass of carbon. The 2 isotopes are C-12 & C-13. % abundance is 98.9 & 1.10. X
.989 =
12 amu
C – 12 =
12 amu
Do the example on worksheet A =
.14 amu
C – 13 = X
13 amu
.0110 + =
12 amu
.14 amu
12.14 amu
12 amu

21. X X = = X + = Examples: Formula: .989 22 amu X – 22 = 22 amu 2.3 amu
% abundance of isotope expressed as a decimal
Mass of the isotope X
Formula:
Determine the atomic mass of element X. The 2 isotopes are X-22 & X-23. % abundance is 98.9 & X
.989 =
22 amu
X – 22 =
22 amu
Element X is Mg =
2.3 amu
X – 23 = X
23 amu
.1010 + =
22 amu
2.3 amu
24.3 amu
24 amu

22. Review: What is the average atomic mass unit for Iron? 55.85
What is the mass # for Iron? 56
What 3 particles make-up the average atomic mass?
From lecture notes
What 2 particles make-up the mass #?

23. U 9 10 Example 92 92 238 146 238.03 92 9 F 19.00 19 9 Atomic Number
Element/Ion
Atomic Number
Atomic Mass
Mass Number
Prot.
Neut.
Elect. U 9 10 92 92
238
146
238.03 92 9 F
19.00 19 9
From lecture notes

24. 1. The mass # is the sum of ______ & ______.
Review
Number your paper 1-5 and just write the answer!
1. The mass # is the sum of ______ & ______.
2. An average atomic mass is the sum of what three things?
3. Which subatomic particle identifies an element?
4. Which subatomic particle determines the reactivity of an element?
5. Who discovered the electron? What type of ray did he observe?

25. instructions? 1. Dalton wrote which theory?
Review
Answer the following quest. on the blank sheet of paper.
1. Dalton wrote which theory?
2. List the 3 subatomic particles.
3. Which two subatomic particles make-up the nucleus?
4. A negatively charged particle is called an ___________.
5. Draw a circle on your paper, inside the circle draw the nucleus, e-, p+ and n0 for the atom Carbon.
instructions?

26. 6. Most of the mass of an atom is found where?
Review
Directions: # paper 6-10, write just the answer
6. Most of the mass of an atom is found where?
7. Whose theory states that all atoms of the same element are identical?
8. Which experiment led to the discovery of the nucleus?
9. What is the charge on the nucleus? What cancels out this charge?
10. A cathode ray proved the presence of an _____ & a canal ray showed ___ were present in an atom. What piece of equipment was used?

27. Take out your homework problems
instructions?