Mr. Matthew Totaro Legacy High School Honors Chemistry Periodic Families and Mendeleev Mr. Matthew Totaro Legacy High School Honors Chemistry

Dmitri Mendeleev Ordered elements by atomic mass. Saw a repeating pattern of properties. Periodic law —When the elements are arranged in order of increasing relative mass, certain sets of properties recur periodically. Used pattern to predict properties of undiscovered elements. Where atomic mass order did not fit other properties, he reordered by other properties. Te & I

Mendeleev’s Periodic Table

Mendeleev's Predictions

Periodicity Periodic = repeating When one looks at the properties of elements, one notices a repeating pattern of characteristics & reactivities. Periodic = repeating

Periodicity = Metal = Metalloid = Nonmetal

Metals Solids at room temperature, except Hg. Reflective surface = Luster. Shiny Conduct heat. Conduct electricity. Malleable. Can be shaped. Ductile. Drawn or pulled into wires. About 75% of the elements are metals. Lower left on the table.

Nonmetals Found in all 3 states. Poor conductors of heat. Poor conductors of electricity. Solids are brittle. Upper right on the table. Except H.

Properties of Silicon: Metalloids Show some properties of metals and some of nonmetals. Also known as semiconductors. Properties of Silicon: Shiny Conducts electricity Does not conduct heat well Brittle

The Modern Periodic Table Determined the atomic numbers of elements from their X-ray spectra (1914) Arranged elements by increasing atomic number Killed in WW I at age 28 (Battle of Gallipoli in Turkey) H.G.J. Moseley (1887- 1915) while doing post-doctoral work (with Ernest Rutherford) bombarded X-rays at atoms in increasing number and noted that the nuclear charge increased by 1 for each element. This gave him the idea to organize the elements by increasing atomic number. Periodic law – elements organized by increasing atomic number on periodic table (1913) In 1913, Moseley analyzed the frequencies of X -rays emitted by the elements and discovered that the underlying foundation of the order of the elements was atomic number, not atomic mass. Moseley hypothesized that the placement of each element in his series corresponded to its atomic number Z, which is the number of positive charges (protons) in its nucleus. Moseley- wavelengths in X-rays determined by the number of protons in the nucleus of the anode atoms - change anode, change wavelength Henry Moseley

The Modern Periodic Table Elements are arranged from left to right in order of increasing atomic number There are 18 vertical columns called Families There are 7 horizontal rows called Periods.

Long Form of the Periodic Table

The Modern Periodic Table Main group = representative elements = “A” groups Transition elements = “B” groups all metals Bottom rows = inner transition elements = rare earth elements metals really belong in Period 6 & 7

find table that includes rare earth elements

Families of the Periodic Table

= Alkali metals = Alkali earth metals = Noble gases = Halogens = Lanthanides = Actinides = Transition metals add pictures of elements from text Tro: Chemistry: A Molecular Approach, 2/e

Important Groups - Hydrogen Nonmetal Colorless, diatomic gas very low melting point and density Excited Hydrogen Gas

Important Groups – Alkali Metals Group IA = Alkali Metals Hydrogen usually placed here, though it doesn’t really belong Soft, low melting points, low density Flame tests ® Li = red, Na = yellow, K = violet Very reactive, never find uncombined in nature lithium sodium potassium rubidium cesium

Important Groups - Alkali Earth Metals magnesium calcium beryllium strontium barium Group IIA = Alkali Earth Metals harder, higher melting, and denser than alkali metals Mg alloys used as structural materials flame tests = Ca = red, Sr = red, Ba = yellow-green reactive, but less than corresponding alkali metal

Important Groups – Halogens Group VIIA = halogens Nonmetals Only family with solids, liquids, and gases All diatomic Very reactive fluorine chlorine bromine iodine astatine

Important Groups - Noble Gases helium neon argon krypton xenon Group VIIIA = Noble Gases all gases at room temperature very low melting and boiling points very unreactive, practically inert very hard to remove electron from or give an electron to

States of the Elements (at STP) Orange = Solid Red = Liquid Purple = Gas