The Periodic Table Organizing the Elements

Basic Layout The Periodic Table consists of 18 vertical columns called Families or Groups As well as 7 horizontal rows called Periods or Series

The First Periodic Table ‣ Developed by Dmitri Mendeleev in ‣ Organized elements by order of increasing mass ‣ Revealed the Law of Periodicity (repeating patterns in the properties of elements)

Families (or Groups) of Elements Groups of elements are numbered from left to right, from 1 to 18

Elements in the same Family (or Group) Share similar chemical and physical properties This is due to their identical outer electron arrangement (these outer electrons are called valence electrons) Lithium Sodium Potassium

Periods (or Series) of Elements The two detached rows at the bottom of the Periodic Table are actually a part of Periods 6 and 7. They are placed at the bottom for convenience. The Periodic Table would be much wider if they were placed in the spot marked in orange.

Most of the elements on the Periodic Table are metals

Metals and Nonmetals The red staircase line divides the metals from the nonmetals. Metals are located on the left, nonmetals on the right. The only exception to this division is the element Hydrogen, which is located in the upper left corner. H

Naturally Occurring Elements Another important group …doesn’t exist as single atoms …but as two atoms joined together. Diatomic Gases 9

Figure 3.14: Nitrogen gas contains NXN molecules. 10

Figure 3.14: Oxygen gas contains OXO molecules. Copyright © by McDougal Littell. All rights reserved. 11

“Silly Seven” 12

Many of the groups of elements have special names “Halogens” “Noble Gases” “Transition Metals” “Alkaline Metals” “Metalloids”

Each of these families is made up of several elements that share some fairly unique properties. In fact, elements are grouped on the Periodic Table according to their shared properties. Elements within a family are very similar to one another.

Alkaline Metals Group 1 ‣ VERY reactive ‣ Soft metals ‣ Lithium, Sodium, Potassium Potassium reacting violently with water

Alkaline Earth Metals Group 2 ‣ Not as reactive as Group 1 ‣ Fairly soft metals Magnesium reacting with air

Transition Metals Groups ‣ Varied properties ‣ Tend to show extremes of metals (highest density, melting point, etc.)

Halogens Group 17 ‣ VERY Reactive ‣ State of matter varied (two gases, a liquid, and 2 solids)

Noble Gases Group 18 ‣ Non-reactive (inert) ‣ Will not form compounds with other elements