The Periodic Table The Periodic Table The Periodic Table The Periodic Table With due credit to the extraordinary PeriodicTable.comWith due credit to the extraordinary PeriodicTable.comWith due credit to the extraordinary PeriodicTable.comWith due credit to the extraordinary PeriodicTable.com

History of the Periodic Table

History of the Periodic Table

•Dmitri Mendeleev developed first periodic table where elements were arranged according to increasing atomic mass. Spaces in table due to unknown elements predicted by Mendeleev...

•Henry Moseley rearranged the Periodic Table so elements are arranged according to increasing atomic number (the number of protons)

•Arrangement by atomic number is better than arrangement by atomic mass because no element will ever have the same number of protons but elements may have similar atomic mass may vary due to varying numbers of neutrons in isotopes

Conventions of the Periodic Table

Conventions of the Periodic Table

• Elements are arranged by groups and periods...

•Groups are vertical and elements have the same number of valence electrons in the outer orbital

•Periods are horizontal and elements are arranged by increasing atomic number (the number of protons)

•Element keys may be colored based on metal, metalloid, and nonmetal classification of elements

•Element keys may also denote if element is a solid, liquid, or gas at room temperature

Example of Element Key

Two major groups of elements…

Two major groups of elements…

Representative elements and transition elements

Group 1: Alkali Metals Group 1: Alkali Metals

• One valence electron in outer orbital, therefore very reactive!

• Silvery solids with low densities and low melting points

• Increase in reactivity as you move down the group, therefore Francium will be the most reactive

• Although hydrogen is in Group 1, it is not an alkali metal! It is just a gas with one valence electron in its outer shell...

Group 1: Alkali Metals Group 1: Alkali Metals • Lithium is using lithium

batteries

•Sodium complexes with chlorine to form table salt

•Potassium is found in potatoes and bananas

Group 2: Alkaline Earth Metals

Group 2: Alkaline Earth Metals

• Two valence electrons in outer orbital, therefore less reactive than group 1 elements

• Denser, harder, with a higher melting point than alkali metals in the same period

Group 2: Alkaline Earth Metals

Group 2: Alkaline Earth Metals • Beryllium is found in gems

like emeralds and aquamarines

•Magnesium is an important element in chlorophyll, the light-capturing pigments in green plants

•Calcium is important in bones and teeth

Groups 3-12: Transition Elements

Groups 3-12: Transition Elements

•Number of valence electrons in outer orbital varies

•All are metals, therefore they are solids that are malleable, ductile, and conduct electricity and heat

•Most have higher melting points than representative elements

Groups 3-12: Transition Elements

Groups 3-12: Transition Elements

• The Iron Triad (iron, cobalt, and nickel) are magnetic metals

• Iron is necessary to carry oxygen in hemoglobin and is used with other elements to make steel

•Mercury has the lowest melting point of any metal and is liquid at room temperature

•The Platinum Group, including platinum and iridium, maybe used as catalysts (substances that decrease the activation energy needed to start a chemical reaction)

Groups 3-12: Inner Transition Elements Groups 3-12: Inner

Transition Elements Lanthanide Series - Very soft... May be cut with a knife and difficult to separate from other elements (complexes like Play-doh)

Actinide Series - All are radioactive

Lanthanide Series Actinide Series

Lanthanide Series Lanthanide Series

• Originally named the rare earth metals, but then geologists realized the Lanthanides are not so rare...

•Cerium is more prevalent in the Earth's crust then lead, and is used to make flint for lighters

Actinide Series Actinide Series

• Thorium, protactinium, and uranium are naturally found on Earth

•Half-life of uranium is 4.5 billion years

•All other actinides are synthetic elements made by colliding nuclei of atoms using a particle accelerator... Synthetic products may be very unstable and break down into other elements within seconds!

Group 13: Boron Group Group 13: Boron Group

•Three valence electrons in outer orbital, therefore even less reactive than groups 1 & 2

•Group 13 contains one metalloid and four metals...

•Boron is a brittle black metalloid often used in making pots and pans that may tolerate large temperature changes over a short time (refrigerator to oven)

•Aluminum is used to make soda cans, cookware, baseball bats, housing siding, and of course, aluminum foil

Group 14: Carbon Family

Group 14: Carbon Family

• Four valence electrons in outer orbital, therefore not very reactive due to energy necessary to gain or lose four electrons...

• Group 14 consists of one nonmetal, two metalloids, and two metals

• Carbon is the element necessary for all organic molecules. It's small atomic mass and the ability to form four covalent bonds enables it to form a wide variety of complex molecules...

• Silicon & Germanium are both metalloids used in industry as semiconductors because they can conduct electricity in small amounts and not generate a lot of heat. Silicon found in sand is used to make glass...

Group 15: Nitrogen Group

Group 15: Nitrogen Group

•Five valence electrons in outer orbital, therefore more reactive than group 14

•Group 15 contains two nonmetals, two metalloids, and one metal

•Nitrogen is a nonmetal gas that comprises about 80% of air, is converted by bacteria from nitrogen gas to organic nitrogen compounds, and is necessary for making proteins in the body

•Phosphorus is flammable when it combines with oxygen and is used for making matches... Phosphorus is also necessary for mineralization in teeth & bones, production of ATP, and building DNA

Group 16: Oxygen Group

Group 16: Oxygen Group

•Six valence electrons in outer orbital, therefore more reactive than group 15, but less reactive than group 17

•Group 16 contains three nonmetals and two metalloids

•Oxygen is a nonmetal gas that comprises about 20% of the air. Oxygen is necessary for combustion to occur, for the formation of ozone in the upper atmosphere of the planet (which protects living organisms from harmful radiation from the Sun), and for all organisms who perform aerobic respiration (like us...)!

•Sulfur is a yellow nonmetal usually produced in areas of volcanism, and used to make a variety of chemicals in industry

•Selenium conducts electricity in the presence of light and is used to make solar cells

Group 17: Halogen Group

Group 17: Halogen Group

• Seven valence electrons in outer orbital, therefore very reactive! Reactivity increases towards the top of the group...

• Group 17 elements are all non-metals that form salts with alkali metals. Halogen means "salt former"

• At room temperature, Fluorine & Chlorine are gases, Bromine is a liquid, Iodine & Astatine are solids

• Chlorine is added to water to kill bacteria

• Iodine is used by the thyroid to make hormones needed by the body

Group 18: Nobel Gases Group 18: Nobel Gases • Eight valence electrons in outer orbital, therefore not very

reactive (inert)...

• Glass tubes filled with gas glow when electricity passes through the gas

• Noble gases (Neon, Argon, and Krypton) are used in neon lights, strobe lights, and in lights on airport runways

• Helium does not burn and is used to fill balloons and blimps

• Radon is a radioactive gas produced from the decay of uranium and can cause lung cancer if inhaled over time