1. Matter Quiz Atomic Theory Notes

2. Warm - Up
Place your electronic device in Mr. Klotz’s bin when you come into class.
Make sure your device is on silent
If I have silver jewelry is it a homogeneous or heterogeneous?
What about air?
Any last minute questions?

3. Objective Today I will be able to:
Demonstrate knowledge of matter and energy by taking a quiz
Identify the parts of the atom and their isotopes
Calculate atomic masses of isotopes given a set of data

4. Homework
Atomic Structure Practice

5. Agenda Warm – Up Matter Quiz Atomic Theory Notes
Atomic Theory Practice
Exit Ticket

6. Atomic Theory Notes

7. Modern Atomic Theory
Atom – smallest part of matter that represents a particular element
Composed of electrons, protons, and neutrons
Protons and neutrons (nucleons) form the nucleus of an atom
Mostly empty space

8. Subatomic Particles Name Symbol Charge Proton p+ +1 Neutron n Electron
Electron e- -1

9. 9.109 x 10-28 (considered to be zero)
Subatomic Particles
Name
Mass (g)
Mass (amu)
Location
Proton
1.673 x 10-24 1
Nucleus
Neutron
Electron
9.109 x (considered to be zero)
.0005
Outside Nucleus

10. What information can we get from the periodic table?

11. Atomic Number number of protons in the nucleus
You cannot change the number of protons!!!
Determines the identity of an element
Also the number of electrons in a neutral atom

12. Atomic Number What is the atomic number of carbon?6
How many protons and electrons would there be in a neutral atom of carbon?
6 protons and 6 neutrons
How many protons and neutrons would there be in a neutral atom of oxygen?
8 protons and 8 neutrons

13. Atomic Mass Measured in atomic mass units
The number or protons and neutrons in an atom

14. How did we arrive at measuring atomic mass in atomic mass units?
Based on the Carbon-12 scale
By international agreement, a carbon atom contains 6 protons and 6 neutrons, or 12 amu
Therefore, 1 amu is 1/12 of a carbon atom
Since the mass in grams of protons and neutrons are about the same, they both have an atomic mass unit of 1

15. Why aren’t electrons accounted for in the calculation of the atomic mass?
Electrons are small!
It takes almost 2,000 electrons to equal the mass of one proton or neutron
Electrons are assumed to have a mass of 0 amu

16. If each proton and neutron has a mass of one amu, then why aren’t the atomic masses on the periodic table whole numbers?
Isotopes of elements
atoms with the same number of protons but different numbers of neutrons

18. Isotopes Some isotopes are found more common than others
We can determine which isotope is more common by looking at the atomic mass
Atomic Mass is calculated weighted averages

20. How do we calculate a weighted average?
Category
Score
Exams (50%)
80%
Labs (25 %)
75%
Classwork (15 %)
95%
STEM fair (10 %)
87%
(.50 x 80) + (.25 x 75) + (.15 x 95) + (.10 x 87) =
81. 7 % = 82 %

21. Atomic Mass is calculated using the same method of weighted averages
Carbon Isotope
C – 14 1%
C - 12
99%
(.01 x 14) + (.99 x 12) =
12.02 amu

22. Ions When an atom gains or loses an electron, an Ion is formed
Cation – atom loses an electron and makes a positive ion
Example: Lithium (Li) loses one electron
It becomes Li+
Anion – atom gains an e- and makes a negative ion
Example: Sulfer (S) gains two electrons
It becomes S-2

23. Ions Examples What is the chemical symbol for the ion with:
13 protons and 10 electrons
- Al+3
7 protons and 10 electrons
- N-3

24. How many protons and electrons are present in a(n):
S-2 ion
- 16 p+ and 18 e-
Li+1 ion
- 3 p+ and 2 e-

25. Be careful with terminology!
Atomic Mass – average mass of the naturally occurring isotopes of an element
Seen on the periodic table
Mass Number – number of protons and neutrons in an atom’s nucleus
Seen in symbolic representations

26. Symbolic Representations of Elements
An atom with 7 protons and 7 neutrons has a mass number of 14 and is usually written as… N 14 7

27. Al+3 Se-2 How many protons, neutrons, and electrons?27
Al+3 13
13 p+, 14 n, and 10 e- 79
Se-2 34
34 p+, 45 n, and 36 e-

28. Exit Ticket
Draw the symbolic representation of the K1+ ion