1. Atomic Structure

2. Atomic Notation
Atomic Notation represents the number of protons and neutrons in the nucleus of an atom
The Atomic Number, Z, represents the number of protons in the nucleus. It also represents the number of e- in a neutral atom.
The Mass Number, A, represents the total number of protons and neutrons in the nucleus of an atom

3. Atomic Notation Atomic Number is 11
# of p+ = 22 protons; # e- = 11 electrons
The Mass number is 23
#n= 23-11=12 neutrons

4. Atomic Notation Find the Number of protons Number of neutrons
Number of electrons
Atomic number
Mass number

5. Atomic Notation
If an element has an atomic number of 34 and a mass number of 78 what is the
Number of protons
Number of neutrons
Number of electrons
Complete symbol?

6. Isotopes
Atoms of the same element can have different numbers of neutrons (Dalton was wrong)
These atoms of the same element would have different mass numbers
These “cousins” of the same element are called isotopes
Most elements occur naturally with varying number of neutrons

7. Hydrogen Isotopes Hydrogen has 3 Isotopes
1 proton and 0 neutrons, protium
1 proton and 1 neutron, deuterium
1 proton and 2 neutrons, tritium (radioactive)

8. Naming Isotopes
To name an isotope properly, we put the mass number after the name of the element
Carbon-12 (6 protons and 6 neutrons)
Carbon-14 (6 protons and 8 neutrons)
Uranium-235 (92 protons and 143 neutrons)

9. Practice Write the symbol for Cobalt-60
How many protons and neutrons does an atom of mercury-202 have?
How many electrons are present in an atom of Copper-63?

10. Measuring Atomic Mass
All of the elements on the Periodic Table have a Mass Number that is in decimal form, or not a whole number… why?
The Mass number reported on the periodic table is a “weighted average” of the isotopes that are naturally occurring

11. Measuring Atomic Mass
The Mass Number= the Atomic Mass, or Atomic Weight
The mass of 1 mole of an element (unit 4)
The number of neutrons and protons present
The mass of one atom of an element relative to an atom of another element
Unit: Atomic Mass Unit (amu)
The standard for the amu scale is Carbon:
Carbon= 6p+ and 6n0= mass standard of 12 amu
All other atoms are designated relative to Carbon. I.e. Hydrogen is 1/12th the mass of carbon (or Atomic Mass 1 amu

12. Mathematics of Isotopes
A weighted average means that the numbers of all the objects are not equal, but occur in different amounts
Calculated by multiplying the percent of the object (as a decimal number) by its mass for each object and adding the numbers together

13. Mathematics of Isotopes
Copper has 2 isotopes:
Copper-63 with a mass of amu and 69.09% abundance
Copper-65 with a mass of amu and 30.91% abundance
𝑎𝑚𝑢 𝑎𝑚𝑢 =63.55 𝑎𝑚𝑢

14. Isotope Examples
Magnesium has 3 isotopes % Magnesium-24 with a mass of amu, Magnesium-25 with a mass of amu, and the rest Magnesium-26 with a mass of amu. What is the atomic mass of Magnesium?
Boron is 20% B-10 and 80% B-11. What is the Atomic Mass of Boron?

15. Ions
Result from loss or gain of e- by an atom

16. Ions
𝟑𝟓 𝟏𝟕 𝐂𝐥 −

17. Ions
What is the standard atomic notation for the aluminum atom and ion?