IIIIII Unit XI: Periodic Properties I. History (p )

A. Mendeleev zDmitri Mendeleev (1869, Russian)  Elements were put in order of increasing atomic mass.  Elements with similar properties were grouped in columns. In some places, masses don’t go in order to complete the pattern. These elements were still assigned to the column their properties matched. (On the assumption that there must be errors in their masses.)

A. Mendeleev zMendeleev’s table was a major breakthrough because it could predict element properties.  Mendeleev left gaps in locations where no known element had the necessary properties to fit the pattern.  Based on the patterns he’d identified, he predicted properties of three of the “missing” elements.

A. Mendeleev zMendeleev’s predicted elements were later discovered/identified and were found to have the properties he’d predicted.

B. Moseley zHenry Moseley (1913, British) (Built on Bohr’s principles of emission spectroscopy) yUsed x-ray spectrometry to determine the number of protons in each element. xThis generated the values we now call “atomic number.” (These were not known in Mendeleev’s time.)

B. Moseley zOrganized elements in the periodic table by increasing atomic number. yThis resolved the mass discrepancies in Mendeleev’s arrangement. yThe Modern Periodic Law: xWhen elements are ordered by atomic number, chemical and physical properties recur periodically.

B. Moseley zThe Modern Periodic Law is sometimes stated: The properties of the elements are periodic function of their atomic numbers. Graphing by atomic number shows repetitive patterns in element properties.

IIIIII I. Periodic Table Vocabulary Ch. 5 - The Periodic Table

B. Blocks s p d f

zMain Group Elements zTransition Metals (d- block) zInner Transition Metals (f-block) B. Blocks

 A group or “family” is a column on the periodic table, e.g., the alkali metals or the noble gases. B. Groups

 A period is a row on the periodic table– all the way across, regardless of block. B. Groups Period 6 includes 6s, 5d, 6p and 4f Period 4: 4s, 3d, 4p

IIIIII II. Organization of the Elements Ch. 5 - The Periodic Table

zMetals zNonmetals zMetalloids A. Metallic Character

 Alkali metals  Alkaline earth metals  Transition metals  Lanthanides  Actinides Periodic Table Sections  Other metals  Metalloids  Other nonmetals  Halogens  Noble Gases

 Elements within a GROUP have similar properties  Because they have similar electron arrangements. Periodic Table Sections 1s 1 2s 1 3s 1 4s 1 5s 1 6s 1 7s 1

 Periodic = every so often  When elements are arranged in order of atomic number, elements with certain properties recur periodically. The Periodic Table There is a predictable pattern. It repeats for each PERIOD.

The Periodic Table Period 3 Na Mg Al Si P S Cl Ar In a PERIOD, atomic radius decreases as atomic number increases.

Atomic Radius Group 1 H Li Na K Rb Cs In a GROUP, atomic radius increases as atomic number increases.

Ionization Energy Period 3 Na Mg Al Si P S Cl Ar In a PERIOD, ionization energy increases as atomic number increases. (But not smoothly.)

Atomic Radius Group 1 H Li NaKRb Cs In a GROUP, ionization energy decreases as atomic number increases. Fr