Periodic Table of Elements

Lothar Meyer (1835-1895)	Dimitri Mendeleev (1834-1907)
Organized elements by atomic mass Saw pattern in behaviors Problem: Only used known elements, so unknown elements could not be predicted	Added to the work of Lothar Meyer Organized elements by mass and properties (such as reactivity) Saw pattern in behaviors Left gaps in the table for unknown elements Allowed unknown elements to be predicted Credited with creating the periodic table
Think of putting all your clothes away until your drawers are full. Then, you buy new clothes and have no place to put them. You then need to reorganize all your clothes in order to make the new clothes fit.	Think of putting together a jigsaw puzzle. You put pieces together based on colors and the pictures on them. You leave empty spaces when a piece doesn't fit. You can guess what a missing piece looks like based on the other pieces nearby.

Classification Legends

Metallic Character	Reactivity	Location on Periodic Table	Percent of Elements
Metals	Generally Lose Electrons When Bonding	To the left of the "stairs"	About 80% of Elements
Semi-Metals (Metalloids)	May act as either a metal or non-metal	Touching the flat parts of the "stairs"	About 6% of Elements
Non-Metals	Generally Gain Electrons When Bonding	To the right of the "stairs"	About 8% of Elements
Noble Gases	Generally Do Not React	Group 18 Elements	About 6% of Elements

* Periods (rows), Group/Family (column)

 

Group #	Group Names (Based on background color in the periodic table above)	# Valence e-	Oxidation #	Special Elements to Know
1	Alkali Metal	1	1+	Francium (most reactive metal); Sodium (Na), Potassium (K)
2	Alkaline Earth Metal	2	2+	---
3-12	Transition Metal	(must be given to you)	(must be given to you)	Copper (Cu), Iron (Fe)
13	---	3	3+	Semimetals (B) [for simplicity, we include Al]
14	---	4	4+ (4-)	Semimetals (Si, Ge)
15	---	5	3-	Semimetals (As, Sb)
16	---	6	2-	Semi-metals (Te, Po)
17	Halogen	7	1-	Fluorine (most reactive non-metal); Semimetals [for simplicity, we include At, Ts]
18	Noble Gas	8 (except He: 2)	0	Do Not React (under normal conditions) Full outer shell

Periodic Trends

• The periodic table is loaded with various patterns, which is one reason it's so useful. There are many patterns.
• Some of these trends run from the left side to the right side, while others run from the top to the bottom.
• If you are asked for a pattern that runs in an opposite direction (i.e. right to left), simply reverse the pattern.
• Many of these trends can be discovered in your reference table using either the Periodic Table itself or Reference Table S.
• Keep in mind that these are general patterns and exceptions will exist.

Property	Pattern Top to Bottom ↓	Pattern Left to Right →
atomic number	increases	increases
atomic mass	increases	increases
valence electrons	remains the same	increases
metallic character (Fr)	increases	decreases
nonmetallic character (F)	decreases	increases
energy levels (rings)	increases	remains the same
*electronegativity	decreases	increases
*first ionization energy	decreases	increases
ionic radius	increases	increases
*atomic radius	increases	**decreases**

* can be found on Reference Table S
** this decreases because there are more protons pulling in on the rings

Periodic Table