1. Chapter 4 - 2 Warm - Up 1. Describe the different parts of an atom.
2. What did Bohr’s model of an atoms resemble?
3. How many electrons does the 2nd energy level hold?
4. What does a p orbital look like?

2. Chapter 4 – 2 Atoms and the Periodic Table
A Guided Tour of the Periodic Table

3. Organizing the Table Groups similar elements together
Elements represented by symbols
Order based the number of protons

4. Periodic Law
Periodic Law – Repeating chemical and physical properties of elements change periodically with the atomic number of the elements.

5. Electron Arrangement Periods – horizontal row of elements
# of protons and electrons increase from left to right

6. Electron Arrangement

7. Organizing into Groups
Group – vertical column of elements
Same # of valence electrons
Determines chemical properties

8. Ions Group 1 elements Ionization – atoms with outer shell not filled
Reactive because outermost energy level has 1 e-
Ionization – atoms with outer shell not filled
Gain or lose e-
No longer has the same # of p+ and e-

9. Ion Ion – atom that has lost or gained one or more electrons
Has a charge

10. Lithium Reaction Lithium – Group 1 Reacts with air or water vapor
Single valence e-
Reacts with air or water vapor
Cation – positive ion
Li+

11. Lithium Cation

12. Fluorine Reaction Fluorine – Group 17
Needs 1 e- to have a complete energy level
Anion – gains an electron to become a negative ion F-

13. Atomic Number
Atomic Number – number of protons in nucleus

15. Atomic Mass Nucleus - contains most of the mass of the atom
Protons and neutrons - far more massive than electrons.
1,836 times larger than an electron.
Proton mass = Neutron mass

16. Atomic Mass
Mass number – sum of the # of protons and neutrons in the nucleus
Atomic mass unit (amu).

19. Mass Number
Mass number = # of protons in atom + # of neutrons in atom.

20. Calculating the # of Neutrons
Neutrons = Mass # - Atomic #

21. Isotopes
Isotopes - Atoms of the same element that have different numbers of neutrons
Name of the element followed by the mass number of the isotope to identify each isotope
Example: Hydrogen-2 and Hydrogen-3.

23. Identifying Isotopes
Average atomic mass – weighted average mass of the mixture of its isotopes.