Periodic Table

The Periodic Law

• Elements are arranged by increasing atomic number• What is atomic number?

• Period – A row in the table of elements• Varies in number of available orbitals (this will make

sense later)

• Group – A column in the periodic table• Elements within a group have similar properties

• Periodic Law – Patterns of repeating properties

Atomic Mass

• All Periodic Tables usually contain: 4 pieces of information:

• Name of the Element• Symbol of the Element• Atomic Number• Atomic Mass – Average distribution of naturally

occurring masses and their isotopes

Classes of Elements

• Metals • Good conductors of electricity and heat• Most are malleable, ductile, solid at room temperature (except for mercury)

• Transition Metals• Able to form compounds with distinctive colors• Iron or chromium can make glass green• Copper or gold can make glass red• Cobalt makes glass blue

• Nonmetals• Poor conductors of heat and electricity• Low boiling points, some are gases at room temperature, brittle (if solid at

room temp)

• Metalloids• Have properties that fall between those of metals and nonmetals

• Properties become LESS METALLIC AND MORE METALLIC across a period

Valence Electrons

• Valence Electrons – an electron that is in the highest occupied energy level of an atom• Play a key role in chemical reactions• Valence electrons INCREASE across a period• Elements in a group have similar properties because

they have the same number of valence electrons

Alkali Metals

• Look at your Periodic Table• Group 1• Called ALKALI METALS• Have 1 valance electron• Extremely reactive• Found in nature only in compounds• Example• Table Salt – Sodium Chloride - NaCl

Alkaline Earth Metals

• Group 2• Called ALKALINE EARTH METALS• Have 2 valance electrons• Very reactive• Reacts with water• Example• Calcium have essential biological functions (Calcium

Carbonate CaCO3)

The Boron Family

• Group 3• Called the Boron Family• Have 3 valance electrons• Contains metals and metalloids• Example• A compound of boron, silicon, and oxygen is used to make

a type of glass that does not shatter easily when it undergoes a rapid change in temperature

The Carbon Family

• Group 4• Called the Carbon Family• Have 4 valance electrons• Contains nonmetals, metals, and metalloids• Example• Silicon carbide – used to tip saw blades, making them last

longer than steel blades

The Nitrogen Family

• Group 5• Called the Nitrogen Family• Have 5 valance electrons• Contains nonmetals, metals, and metalloids• Example• Red phosphorus is used on match tips to ignite them.

The Oxygen Family

• Group 6• Called the Oxygen Family• Have 6 valance electrons• Contains nonmetals and metalloids• Example• Sulfuric acid is used to make fertilizers

The Halogens

• Group 7• Called the Halogens• Have 7 valance electrons• Contains nonmetals• Example• Fluorine is used to prevent tooth decay

The Noble Gases

• Group 8• Called the Noble Gases• Have 8 valance electrons• Contains nonmetals• Example• Used in neon signs• Helium – pink• Neon – orange/red• Argon – purple• Krypton – white• Xenon - Blue

Octet Rule

• Octet Rule – The tendency for all elements to want to have EIGHT electrons by gaining or losing electrons and forming ions

• Ion – An atom or group of atoms that has a positive or negative charge

Practice

How many valence electrons are in the following elements?

1. Si

2. Selenium

3. I

4. Astatine

5. Rn

6. Barium

7. Fr

8. Tl

9. Lead

10. Antimony