Electrons and Periodic Behavior Cartoon courtesy of NearingZero.net

Orbital filling table

Electron configuration of the elements of the first three series

Chemical Symbols Symbols used in the 18 th Century Antimony WaterSulfuric acidCopperSulfur Symbols used by John Dalton Carbon Hydrogen Oxygen Silver Sulfur Nitrogen S Lead Mercury Copper C L Gold Potassa Soda G WaterCarbon dioxideAlcohol Brownlee, Fuller, Hancock, Sohon, Whitsit, First Principles of Chemistry, 1931, page 74

Mendeleev’s Periodic Table Dmitri Mendeleev

Modern Russian Table

Greek Elements Greek Elements

A Spiral Periodic Table

“Mayan” Periodic Table

Alchemy !! Alchemy !!

The Periodic Table Period Group or family Period Group or Family

Easily lose valence electron (Reducing agents) React violently with water Large hydration energy React with halogens to form salts The Properties of a Group: the Alkali Metals

Potassium Metal in Water Newmark, CHEMISTRY, 1993, page 25

Groups/Families on the Periodic Table  Noble Gases: Family18  Alkali Metals: Family 1 in pure state they all have a silvery appearance and are soft enough to cut with a knife in pure state they all have a silvery appearance and are soft enough to cut with a knife Extremely reactive so aren’t found as free elements Extremely reactive so aren’t found as free elements

Noble Gases Noble Gases

Groups/Families on the Periodic Table  Alkaline-earth metals: Group 2 harder, denser, and stronger than group 1 or alkali metals harder, denser, and stronger than group 1 or alkali metals Have higher melting points than group 1, and are less reactive (although still reactive enough not to be found as free elements) Have higher melting points than group 1, and are less reactive (although still reactive enough not to be found as free elements) Halogens: Group 17 Most reactive nonmetals Most reactive nonmetals

Carbon….The Essence of Life Carbon….The Essence of Life

Special elements  Hydrogen and Helium are special b/c although they share some characteristics with their groups/families, they are different b/c they have properties that are not similar to those of ANY group  Hydrogen and helium are the simplest and most abundant elements. Hydrogen makes up 76% of the mass of the universe and helium makes up 23%

Life or Death Elements Life or Death Elements

Properties of Metals  Metals are good conductors of heat and electricity  Metals are malleable  Metals are ductile  Metals have high tensile strength  Metals have luster

Examples of Metals Potassium, K reacts with water and must be stored in kerosene Zinc, Zn, is more stable than potassium Copper, Cu, is a relatively soft metal, and a very good electrical conductor. Mercury, Hg, is the only metal that exists as a liquid at room temperature

Properties of Nonmetals Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.  Nonmetals are poor conductors of heat and electricity  Nonmetals tend to be brittle  Many nonmetals are gases at room temperature

Examples of Nonmetals Sulfur, S, was once known as “brimstone” Microspheres of phosphorus, P, a reactive nonmetal Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure

Properties of Metalloids Metalloids straddle the border between metals and nonmetals on the periodic table.  They have properties of both metals and nonmetals.  Metalloids are more brittle than metals, less brittle than most nonmetallic solids  Metalloids are semiconductors of electricity  Some metalloids possess metallic luster

Silicon, Si – A Metalloid  Silicon has metallic luster  Silicon is brittle like a nonmetal  Silicon is a semiconductor of electricity Other metalloids include:  Boron, B  Germanium, Ge  Arsenic, As  Antimony, Sb  Tellurium, Te

Aspirin Aspirin

Half of the distance between nuclei in covalently bonded diatomic molecule "covalent atomic radii" Periodic Trends in Atomic Radius Radius decreases across a period Increased magnetic attraction Radius increases down a group Addition of principal quantum levels Determination of Atomic Radius:

Table of Atomic Radii

Tends to increase across a period Atoms become closer to a full electron octet in the outer energy level Tends to decrease down a group Outer electrons are farther from the nucleus Ionization Energy - the energy required to remove an electron from an atom Ionization Energy - the energy required to remove an electron from an atom

Table of 1 st Ionization Energies

Ionization of Magnesium Mg kJ  Mg + + e - Mg kJ  Mg 2+ + e - Mg kJ  Mg 3+ + e -

Another Way to Look at Ionization Energy

Electronegativity A measure of the ability of an atom in a chemical compound to attract electrons Electronegativities tend to increase across a period (full octet) Electronegativities tend to decrease down a group or remain the same

Periodic Table of Electronegativities

Summation of Periodic Trends