Groups of the Periodic Table

Aim PT3 – what are the characteristics of the different groups (also known as FAMILIES) in the Periodic Table?

Hydrogen

• Hydrogen belongs to a family of its own.

• Hydrogen is a diatomic reactive gas.

• Diatomic molecule are elements that occur in nature in pairs - Br I N Cl H O F

• Remember the Hindenburg!

• Hydrogen is promising as an alternative fuel for automobiles

Group 1 - Alkali Metals• 1st column on the periodic table

(Group 1) not including hydrogen• One (1) electron in valence shell• Very reactive metals, always

combined with something else in nature (like in salt) (go to vid)

• Soft enough to cut with a butter knife

• Examples– Lithium (Li)– Sodium (Na)– Potassium (K)

Group 2 Alkaline Earth Metals

• Two (2) electrons in valence shell

• Reactive metals that are always combined with nonmetals in nature

• Several of these elements are important mineral nutrients

• Examples:

– Magnesium (Mg)

– Calcium (Ca)

Group 3 – 12 - Transition Metals• All have mobile electrons

– Two outer shells allow electrons to move back and forth between them

– allows heat and electricity to pass through metals easily

• Less reactive, harder metals than Group 1 or 2– Form colored solutions when mixed

with water– High melting points

• Includes metals used in jewelry and construction

Group 13 - Boron Family

• Three (3) electrons in valence shell

• Examples

– Aluminum metal was once rare and expensive, not a “disposable metal”

– Boron – used in nuclear fission reactors as a neutron moderator

Group 14 - Carbon Family

• Four (4) electrons in valence shell

• Contains elements important to life and computers.

• Carbon is the basis for an entire branch of chemistry called organic chemistry

• Silicon and Germanium – important semiconductors

Group 15 - Nitrogen Family

• Five (5) electrons in the valence shell

• Nitrogen makes up over ¾ of the atmosphere

• Nitrogen and phosphorus are both important in living things– Most of the world’s nitrogen is not available to

living things– Legumes (beans and peanuts) contain nitrogen

fixing bacteria so that it is available to plants

• Two thirds of the earth’s population dependent on nitrogen fixing bacteria for their food

Groups 16 - Oxygen Family or Chalcogens

• Six (6) electrons in the valence shell

• Oxygen

– Molecular oxgyen (O2 ) is necessary for respiration

– Ozone (O3 ) protects us from UV radiation

• Many things that stink, contain sulfur

• Ex: rotten eggs, garlic, skunks, etc.

Allotropes

• Elements with

– different physical properties

– But same chemical composition

• Examples

– Carbon – two forms

– Oxygen – two forms

– molecular oxygen and ozone

Group 17 - Halogens• 7 electrons in valence

• Very reactive, volatile, diatomic molecule

• Always found combined with other elements in nature, like salts

• Used as disinfectants and to strengthen teeth

– Flouride in water, toothpaste

– Chlorine bleach, tabs for pool

– Iodine in antiseptics

Group 18 - The Noble Gases

• A full set of 8 electrons in the valence shell

• VERY unreactive, monatomic (only atom per molecule) molecular gases

• Helium – balloons and blimps

• Neon – the glowing signs we all love

• Argon – incandescent bulbs