The Periodic Table

I CAN explain the organization of the periodic table and number the period/series and families/groups.

Mendeleev’s Periodic Table In 1869, a RUSSIAN chemist by the name of DMITRI MENDELEEV made a successful table of the elements. About 60 elements were known by this time. Mendeleev arranged his table from LOWEST ATOMIC MASS NUMBER TO HIGHEST. Elements were placed so that the ones with SIMILAR PROPERTIES formed VERTICAL COLUMNS.

Sometimes he had to leave BLANK SPACES in order to keep all elements with similar properties in the same vertical column. Mendeleev said the blank spaces were for elements that were NOT YET DISCOVERED. Before he died, three new elements were discovered that fit in to his table as he had predicted.

Eventually problems with Mendeleev’s arrangement arose and an ENGLISH scientist named HENRY MOSELEY fixed them by rearraging Mendeleev’s table by INCREASING ATOMIC NUMBER rather than AMN.

Mendeleev had made an important discovery. He noticed that the properties of the elements REPEAT by a pattern. In Mendeleev’s table, properties of the elements were repeated by every 8 th element. This led to the formulation of the PERIODIC LAW.

The Periodic Law The Periodic Law states that the physical and chemical properties of elements repeat regularly when arranged by increasing atomic number.

The Modern Day Periodic Table Today’s periodic table has information on about 106* different elements. Elements are arranged to form HORIZONTAL ROWS across the table and in VERTICAL COLUMNS from top to bottom of the table. –Each element belongs both to a ROW and a COLUMN.

HORIZONTAL ROWS On the PT, a HORIZONTAL ROW of elements [left to right] are knowns as either a PERIOD or SERIES. Across a period or series, the elements transition from being metals on the left side to non-metals on the right side. Characteristics of a PERIOD or SERIES –ANs increase by one from box to box left to right. –Elements slowly change from metals on the left to non-metals on the right. –Each element adds another e- and one or more N o from left to right.

VERTICAL COLUMNS On the PT, a VERTICAL COLUMNof elements [top to bottom] are knowns as either a FAMILY or GROUP. Down a family or group, the elements the elements have very similar CHEMICAL PROPERITES and often similar PHYSICAL PROPERTIES. Characteristics of a Family or Group –Each atom is LARGER THAN THE ONE ABOVE due to added P+, No and e-. – Form chemical bonds in the same manner as the other elements in the group.

Numbering the Periods and Families Each Period/Series and Family/Group has a NUMBER: PERIODS/SERIES are numbered from 1 to 7 down the LEFT side of the table. FAMILIES/GROUPS are numbered from 1-18 across the TOP of the table.

Periods/Series As a general rule, the PERIODS/SERIES do NOT have names, ONLY NUMBERS with the exception of TWO: At the bottom of the table, there are two rows of elements that are removed from the center of the table and placed at the bottom: –The first row is from the 6 th Period (Elements 57-71). –The other row is from the 7 th Period (Elements ) The first row is known as the LANTHANIDE SERIES The second row is known as the ACTINIDE SERIES

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Valence Electrons The periodic table arrangement is based on the arrangement of electrons in an atom’s electron cloud. The properties of an element are a due to the arrangement of electrons in the outermost energy level of the atom.

The outermost energy level is referred to as the VALENCE ENERGY LEVEL and the electrons in this outermost level are called VALENCE ELECTRONS. The number of VALENCE ELECTRONS an atom has can easily be determined from the GROUP NUMBER THE ELEMENT IS IN.

Group 11 valence e- Group 22 valence e-’s TRANSITION ELEMENT [skip for now] Group 133 valence e-’s Group 144 valence e-’s Group 155 valence e-’s Group 16 6 valence e-’s Group 177 valence e-’s Group 188 valence e-’s

Lewis Electron Dot Diagrams Valence electrons [V e- ] are represented by Lewis Electron Dot Diagrams, or Lewis Structures for short. A Lewis Structure consists of the element’s chemical symbol with dots placed around it to represent V e-.