1. Warm Up Monday 1/25/16 1. What are atoms?
2. parts of the atom mass charge
3. Define atomic number.
4. What does the atomic mass indicate?
5. In a atom (no charge) what two sub atomic particles are equal?

2. Isotopes and Mass Number
Leon the Electron
Jimmy Neutron

3. Atomic Number
The number of protons in each atom identifies it as an atom of a particular element
Each atom has a unique number of protons and, in effect, the number of protons cannot change for a particular atom
The Periodic Table is organized by increasing atomic number (left-to-right and top-to-bottom)
All atoms are neutral, so the # protons = the # of electrons because the number of positive charges equals the number of negative charges
Atomic # = # of protons = # electrons
For Helium, the atomic # is 2. So, we know that Helium also has 2 protons and 2 electrons

4. Determining the State of Matter of a Particular Element Using the Periodic Table

5. Protons are the only thing in an atom that does not change.
How Atoms Differ
The order of the elements on the Periodic Table is based on the number of protons in the nucleus.
Protons are the only thing in an atom that does not change.

6. Proton, Neutron, Electron Practice
How many protons does Platinum have?
How many neutrons does Mercury have?
How many electrons does Lead have?
What similarities do these three elements share?
The number of protons in the nucleus is called the atomic number. Also since the positive charges must equal the negative charges to have a neutral atom, and all atoms are neutral, the atomic number will also equal the number of electrons in an atom.
What is the atomic number of
this atom?
What is the element?

7. Don't be an isodope, learn about an isotope.
Isotopes
Don't be an isodope, learn about an isotope.
All atoms of a particular element
have the same number of
protons and electrons
The number of neutrons may
differ
In nature most elements are
found as a mixture of isotopes

9. ? Isotopes and Mass Isotopes differ in mass
Isotopes of an atom have the same chemical behavior. Why? ?

11. Mass Number 10747Ag 10947Ag Mass number = top Atomic number = bottom
Identifies each of the isotopes of an element
10747Ag Ag
Mass number = top
Atomic number = bottom
# neutrons = mass # - atomic #

12. Isotopic Notation Worksheet
Symbol
Isotope Name
Atomic #
# p+
# n0
Mass #
# e- 3H
20F
24Si 56 76

13. Banana Isotope 93.25% of K atoms have 20 neutrons

14. Potassium Isotope protons 19 neutrons 20 21 22 electrons Potassium-39

16. Mass of Individual Atoms
The atomic mass of an element is the weighted average mass of the isotopes of that element
To determine the weighted average atomic mass of an element, calculate the mass contribution of each of the isotopes and add the values together

17. Weighted Average Atomic Mass
3517Cl Cl
Atomic mass: amu Atomic mass: amu
Percent abundance: % % abundance: %
Mass Contribution: Mass Contribution:
(34.969)(.75770)= amu (36.966)(.24230)=8.957 amu
Weighted average atomic mass of chlorine =
( amu amu) = amu

18. Steps to Solving Weighted Averages of Isotopes
1. Turn the % into a decimal for the % abundance.
2. Multiply the decimal by the atomic mass of each particular isotope.
3. Add the masses of the isotopes together.
4. Your answer will be in amu’s (atomic mass units).

19. You try one…..
Calculate the atomic mass of Magnesium. The three Magnesium isotopes have atomic masses and relative abundances of amu (79.99%), amu (10.00%), and amu (11.01%).

20. Weighted Averages of Isotopes Practice I
1. What is the atomic mass of this sample of Silver?
107 Ag amu %
109 Ag amu %
2. What is the average atomic mass of this sample of Hydrogen?
1H %
2H %
3H %

21. Weighted Averages of Isotopes Practice I Continued
3. Boron has two naturally occurring isotopes, Boron-10 (abundance 19.8%, mass = amu, Boron –11 ( abundance 80.2%, mass = amu). Calculate the average atomic mass of Boron.