What is the periodic table? A compact way of organizing the elements that contains a lot of information and allows us to make predictions about the behavior and properties of the elements. Elements

History of the Periodic Table End of the 1700’s – less than 30 elements known. Many elements were discovered during the 1800’s. Many experiments were done to determine atomic masses.

John Newlands - Octaves 1864: Newlands noticed that when the known elements were arranged by atomic masses, their properties repeated every 8 th element. Law of Octaves did not work for all known elements. Key idea was correct: Properties of elements do repeat in a periodic way.

Mendeleev & Meyer 1869: Mendeleev produced 1 st accepted periodic table. Elements ordered by increasing atomic mass into columns with similar properties. PredictedPredicted the existence & properties of undiscovered elements. (Sc, Ge, Ga) Not totally correct. As more accurate determinations of atomic mass were made, several elements weren’t in the right place.

Remember 1860’s: No subatomic particles had been discovered yet. People were going by Dalton’s billiard ball model of the atom.

1913 – Henry Moseley By 1913, protons & electrons discovered. Neutrons predicted. When cathode rays hit stuff, they produce X-rays. Mosely used 30 different elements as “stoppers” Found that the greater the atomic weight of the “stopper,” the shorter the wavelength of the x- rays.

What does any good scientist do? PLOTS THE DATA! Tried correlating the wavelength of the x-ray with the atomic mass of the stopper. Not so nice. Change in much more regular than change in atomic weight.Tried correlating the wavelength of the x-ray with the atomic mass of the stopper. Not so nice. Change in much more regular than change in atomic weight. Then tried correlating the wavelength of the x-ray with an integer, n. Got a very pretty graph.Then tried correlating the wavelength of the x-ray with an integer, n. Got a very pretty graph.

Atomic Number Mosley interpreted the integer, n, to be the positive charge on the nucleus. Mosley suggested that the size of the nuclear charge increased by 1 with each step up the periodic table. (Before, it was organized by atomic weight.)

1913 – Moseley discovers Atomic # Moseley determined that atoms of each element contain a unique number of protons – atomic number. Moseley rearranged Mendeleev’s periodic table by atomic number instead of mass. Problems disappeared.

Periodic Law increasing atomic numberThere is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number.

Glenn Seaborg: 1950’s Lanthanide and Actinide Series

Vocabulary of the P.T. groupsfamiliesColumns are called groups or families. 2 different notations. –1 thru 18, Arabic numerals. –Split into A & B groups. Use Roman numerals I to VIII. A-Group = Columns 1,2,13-18 = representative elements B-Group = Transition metals seriesperiodsRows are called series or periods. Numbered 1 thru 7.

Structure of the Periodic Table Closely related to electron configuration.

Energy Levels = Row Number Elements in the same row have the same number of principal energy levels. (The valence electrons of same-row elements have the same principal quantum number.) The number of principal energy levels is equal to the row number.

Going Across Row 2: FamilyElementConfiguration IALi2-1 IIABe2-2 IIIAB2-3 IVAC2-4 VAN2-5 VIAO2-6 VIIAF2-7 VIIIANe2-8 Which atom is the largest? Li!!

Going Down Column 1: PeriodElementConfiguration 1H1 2Li2-1 3Na K Rb Cs Fr Which atom is the largest? Fr

Valence Electrons Elements in the same column have the same number of valence electrons. GroupNumber of Valence Electrons 1 or IA1 2 or IIA2 13 or IIIA3 14 or IVA4

Valence Electrons Chemical behavior is determined by the number of valence electrons. Elements with the same number of valence electrons will have similar chemical properties. Elements in the same column have similar chemical properties.

Classifying the Elements metals2/3 of the elements are metals. non-metals metalloidsRemaining elements are non-metals and metalloids (semi-metals). Metalloids have some properties of metals and some properties of nonmetals. staircaseKnow the “staircase” dividing line on the P.T. between metals & nonmetals. Everything to left, except H, is a metal.

Properties of Metals Malleable – pounded into sheets Ductile – drawn into wires Have Luster Good conductors of heat & electricity Solids at room temperature, except Hg. “Metals are losers.”Metals lose electrons to form positive ions. “Metals are losers.” Low ionization energy Low electronegativity

Properties of Nonmetals Generally gases or solids, except Br 2. Solids are brittle. Solids are dull. Poor conductors of heat & electricity. “Nonmetals are winners.”Nonmetals gain electrons to form negative ions. “Nonmetals are winners.” High ionization energy. High electronegativity. Properties are the OPPOSITE of metals.

Properties of Metalloids Each metalloid has some metallic and some nonmetallic properties. For example, Si is shiny like a metal but brittle like a nonmetal.

Names of Families Group 1 = Alkali Metals (IA) Group 2 = Alkaline Earth Metals (IIA) Group 17 = Halogens (XVIIA) Group 18 = Noble Gases (XVIIIA or O) –The noble gases are extremely unreactive. Weren’t discovered until 1890’s.

Transition Metals Elements in Columns 3 through 12 Also called the group B elements Transition elements form brightly colored salts and brightly colored solutions. Transition elements may form more than 1 positive ion. Actinide and Lanthanide series = inner transition elements

Elements that are gases at STP H 2, N 2, O 2, F 2, Cl 2 + the noble gases – He, Ne, Ar, Kr, Xe, Rn

Elements that are liquids at STP Br 2 (non-metal) and Hg (metal)

Allotrope Different forms of an element in the same phase. Have different structures and properties.Different forms of an element in the same phase. Have different structures and properties. O 2 and O 3 - both gas phaseO 2 and O 3 - both gas phase Graphite, diamond, buckey balls – all solid phase carbon.Graphite, diamond, buckey balls – all solid phase carbon.

C 60

Graphite and Diamond