The Periodic Table

How Elements Are Organized

• In 1865 John Newlands was the first to organize the elements according to properties and increasing atomic mass– In studying this, he found that properties

repeated every eight elements – The Law of Octaves

• In 1869 Dmitri Mendeleev used Newlands research and research of his own to create the first periodic table

How Elements Are Organized

How Elements Are Organized

• Mendeleev did not have all the elements to work with, and some were not yet discovered– He predicted, based on the research and

periodic trends what properties the elements would have

• This idea is called the Periodic Law– Repeating physical and chemical properties

change periodically with their atomic number

How Elements Are Organized

• Henry Moseley used the line-emission spectra to organize the elements– He found that the elements should be

organized on atomic number, not atomic mass

• When this was changed, discrepancies in Mendeleev’s table disappeared

How Elements Are Organized

• To understand why elements have similar properties, you have to study the electron configurations– Elements with similar properties have the

same valence shell• The valence shell is the outermost shell of

electrons• s and p orbitals

How Elements Are Organized

• The periodic table is organized in groups and periods– A group is the vertical column

• Elements in a group will have similar properties

– A period is the horizontal row• Elements in a period will be filling the same

valence shell

Tour of the Periodic Table

Main Block Elements

• The elements in the s and p block are called the main block elements (also known as the main group elements)

• These will be filling up the valence shell

Alkali Metals

• Group 1• Highly reactive with water• http://www.youtube.com/watch?v=Ft4E1eCUItI

• They have one electron in their valence shell

• They are soft, with low melting and boiling points

• Alkali metals color flames– Li red   Na yellow   K lilac   Rb red   Cs blue

Alkaline Earth Metals

• Group 2 Elements• They have a full s orbital

– Have 2 electrons in their valence shell

• Very reactive (less than Alkali Metals)– Usually found in compounds– http://www.youtube.com/watch?v=DFQPnHkQlZM

• Harder and denser than alkali metals, and have higher melting points

• Characteristic colors when heated in a flame: – Mg brilliant white   Ca brick-red   Sr crimson  

Ba apple green

Halogens

• Group 17• Most reactive non-metals• Full s orbital, and only missing one

electron in the p orbital (7 electrons in the valence shell)

• Most often bonded to Alkali Metals• At room temperature all the halogens exist

as diatomic molecules• http://www.youtube.com/watch?v=u2ogMUDBaf4• http://www.youtube.com/watch?v=Qvs4NTB71uY

Noble Gases

• Group 18

• Full Valence Shell– Full s and p orbitals

• Non-Reactive

• Once called inert gases, but found some compounds will form, although very few

Hydrogen

• 1st element on the periodic table

• Does not really fall into any category

• Sometimes acts as a metal, sometimes acts as a non-metal

• Highly explosive• http://www.youtube.com/watch?v=xiAT9xvTVKI

Metals

• Most of the elements are metals

Metals

• Physical Properties of Metals:– Luster (shininess) – Good conductors of heat and electricity – High density (heavy for their size) – High melting point – Ductile (most metals can be drawn out into thin wires) – Malleable (most metals can be hammered into thin

sheets) • Chemical Properties of Metals:

– Easily lose electrons – Corrode easily. Corrosion is a gradual wearing away.

(Example: silver tarnishing and iron rusting)

Metals

• Transition Metals– Summary of Common Properties

• Low ionization energies • Positive oxidation states • Very hard • High melting points • High boiling points • High electrical conductivity • Malleable • Five d orbitals become more filled, from left to right on

periodic table

Metals

• These common properties apply to both the lanthanides and actinides. – The rare earths are silver, silvery-white, or gray metals. – The metals have a high luster, but tarnish readily in air. – The metals have high electrical conductivity. – The rare earths share many common properties. This makes

them difficult to separate or even distinguish from each other. – There are very small differences in solubility and complex

formation between the rare earths. – The rare earth metals naturally occur together in minerals (e.g.,

monazite is a mixed rare earth phosphate). – Rare earths are found with non-metals, usually in the 3+

oxidation state. There is little tendency to vary the valence. (Europium also has a valence of 2+ and cerium also a valence of 4+.)

Metalloids

• Elements on both sides of the zigzag line have properties of both metals and nonmetals. These elements are called metalloids.

• Physical Properties of Metalloids:– Solids – Can be shiny or dull – Ductile – Malleable – Conduct heat and electricity better than nonmetals but

not as well as metals

Nonmetals• Nonmetals are found to the right of the stair-step line. Their

characteristics are opposite those of metals.– Physical Properties of Nonmetals:

• No luster (dull appearance) • Poor conductor of heat and electricity • Brittle (breaks easily) • Not ductile • Not malleable • Low density • Low melting point

– Chemical Properties of Nonmetals:• Tend to gain electrons • Since metals tend to lose electrons and nonmetals tend to gain electrons,

metals and nonmetals like to form compounds with each other. These compounds are called ionic compounds. When two or more nonmetals bond with each other, they form a covalent compound.