Unit 3 – Lesson 1 Periodic Table

Periodic Table Development Lesson 1 Periodic Table Development There are 109 individual squares, each showing the element name, element symbol, atomic number and atomic mass. Some tables show more information.

Dmitri Mendeleev In 1869 he published a table of the elements organized by increasing atomic mass. 1834 - 1907

Henry Moseley In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements. He rearranged the elements in order of increasing atomic number. Henry worked with Ernest Rutherford at his lab. By sorting by positive charge instead of by atomic number, the property/mass problems all worked out. 1887 - 1915

Glenn T. Seaborg After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became known as the Actinide series. 1912 - 1999

Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

The horizontal rows are called PERIODS. Each period represents elements with the same number of shells and with one more shell than the period before it.

The vertical columns are called GROUPS or FAMILIES. Elements in a family have the same number of valence(outer shell) electrons. Hydrogen is really in a group by itself. The vertical columns are called GROUPS or FAMILIES.

Semimetals(Metalloids)-middle Metals-left side Luster, conductors, malleable, ductile, solids Positive ions Nonmetals- right side Dull, insulators, shatter, brittle Negative ions Semimetals(Metalloids)-middle intermediate characteristics Elements touching black “stair-step” line (except Aluminum which is a metal)

Ions  To become stable, atoms gain or lose electrons to fill their outermost energy level (valence shell) with 8 electrons (Octet rule). Metals lose electrons to achieve eight electrons in their valence shell. Nonmetals gain electrons to achieve eight electrons in their valence shell.

Examples What is the electron configuration of Oxygen? 1s2 2s2 2p4 There are 6 e’s in the n=2 energy level so oxygen will gain two e’s to make 8, leaving O-2 What is the electron configuration of Mg? 1s2 2s2 2p6 3s2 Mg will lose the 2 n=3 electrons and therefore have 8 valence electrons as Mg+2

Alkali Metals (Group 1) 1 valence electron Form 1+ ions Found in compounds in nature, very rarely found as pure elements Most reactive metals (explaining above) These were first found in ashes. Properties: soft shiny solids, low density, low melting points, reacts easily with oxygen and group 17. Sodium and potassium are the most abundant, about 3% of ocean by mass. Sodium is produced by passing electricity through table salt. Alkali Metals Demo Sodium Lithium Potassium See attached.

Hydrogen Nonmetal 1 valence electron Forms 1+ or 1- ions Most common element in the universe. Most of it found on earth is in water. Elemental hydrogen can escape earth’s gravity so not much of it is around. Acid/base chemistry is bases on the presents of absence of the hydrogen ion.

Alkaline Earth Metals (Group 2) 2 valence electrons Form 2+ ions Found in compounds in nature, rarely found as pure elements Not as reactive as the Alkali Metals but still quite reactive These have a higher density and melting point than the Alkali metals. They are used mostly for alloys. Beryllium is strong as steel but much lighter. Found in: antacids, limestone, chalk, marble

Boron Family (Group 13 or 3A) 3 valence electrons Contains a metalloid (boron) and metals These are relatively noncorrosive Aluminum ore comes from bauxite ore and is very common

Carbon Family (Group 14 or 4A) 4 valence electrons Contain non-metals, metalloids, and metals CARBON Found in almost everything Basis of organic chemistry SILICON 2nd most abundant element Found in sand glass transistors and solar cells

Nitrogen Family (Group 15 or 5A) 5 valence electrons Has nonmetals, metalloids, and metals NITROGEN 80% of the atmosphere is nitrogen Plants can’t remove nitrogen from the air, they must get their nitrogen from the soil Ammonia is produced in large quantities as a fertilizer. PHOSPHEROUS Needed for strong bones and teeth Also found in fertilizers, detergents, and sour flavors.

Oxygen Family (Group 16 or 6A) 6 valence electrons Contains nonmetals, metalloids and a radioactive element (Po) OXYGEN Most abundant element on earth Combustion is always a reaction with oxygen Ozone (O3) is air pollution SULFUR Also called brimstone and fool’s gold Typically an unpleasant odor Most used to make sulfuric acid

Halogens (Group 17 or 7A) 7 valence electrons Form 1- ions Found in compounds in nature Very reactive Astatine is radioactive Most of these are very colorful. FLOURINE Most reactive and very corrosive. Chlorofluorocarbons (CFC) are linked to the ozone depletion CHLORINE This is the most useful of the halogens Used in disinfectants, salt, PVC pipes and more The others are used in flame retardents, pesticides, photo film

Noble Gases (Group 18 or 8A) 8 valence electrons with the notable exception of helium. Helium has two. Most are non-reactive. All are gases. Argon is the most abundant. The biggest noble gases can be forced to react under the right conditions.

Representative vs Transition Elements Representative (main group or A groups) are groups 1, 2, 13 – 18 Transition (B groups) elements are groups 3 - 12