1. Chemistry Unit: Chapter 3
Periodic Table Part 1

2. Dmitri Mendeleev Noticed some elements behaved the same
Wondered if they could be organized by any specific pattern
Focused on melting point, density, color, atomic mass
Published first periodic table of 63 elements in 1869

3. Modern periodic table Rearranged according to atomic number in 1913
More consistent patterns
Currently a Total of 118 elements

4. How do we find an element?
Periods
Horizontal rows going left and right
Period numbers are down the left side
Groups
Vertical columns going down
Group numbers are across the top of the periodic table
Use them like battleship

5. The element in period 5 group 17 is: I (iodine)
Ca (calcium) 1 18 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 2 3 4 5 6 7

6. How do we read an element’s square?
Always the same information
Read from top to bottom
Tells you 7 things

7. # of protons and electrons
Atomic number =
# of protons and electrons
Atomic symbol
Atomic name
Atomic mass =
# protons + # neutrons

8. Example 79 79 79 Au Gold 197 118 Atomic number = _______
# protons = ______
# electron = ______
Atomic symbol = ______
Atomic name = ______
Atomic mass = ______
# Neutrons = ______ 79 79 Au
Gold
197
118
197 – 79 = 118

9. Left to right, atomic number: Left to right, atomic mass: increases
Down a group:
increases 1 18 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1 2 3 4 5 6 7

10. Left to right, atomic size:
decreases
Down a group, atomic size:
increases