Chemistry Unit: Chapter 3 Periodic Table Part 1

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

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

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

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

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

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

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

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

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