The History of the Modern

Periodic Table

History of the Periodic Table

• Dmitri Mendeleev – first to organize elements according to their properties

• Mendeleev ordered the elements according to increasing atomic mass

Henry Mosely

• British Scientist 1911

• Re-ordered the periodic table in order of Proincreasing atomic number instead of mass.

• blems with the Mendeleev table disappeared.

History of the Periodic Table

• Periodic Law: The physical & chemical properties of the elements are periodic functions of their atomic numbers.

History of the Periodic Table

• Periodic Table: arrangement of elements in order of their atomic numbers so that elements with similar properties fall in the same column.

Periodic Table Geography

The horizontal rows of the periodic table are called PERIODS.

The vertical columns of the periodic table are called GROUPS, or FAMILIES.

The elements in any group of the periodic table have similar physical and chemical properties!

Alkali Metals (yellow)

Alkali Metals

• 1st column on the periodic table (Group 1) not including hydrogen.

• Very reactive metals, always combined with something else in nature (like in salt).

• Soft enough to cut with a butter knife

Alkaline Earth Metals(Blue)

Alkaline Earth Metals

• Second column on the periodic table. (Group 2)

• Reactive metals that are always combined with nonmetals in nature.

• Several of these elements are important mineral nutrients (such as Mg and Ca

Transition Metals (orange!)

Transition Metals

• Elements in groups 3-12• Less reactive harder

metals• Includes metals used in

jewelry and construction.

• Metals used “as metal.”

Halogens (green)

Halogens

• Elements in group 17• Very reactive, volatile,

diatomic, nonmetals• Always found combined

with other elements in nature .

• Used as disinfectants and to strengthen teeth.

Noble Gases (Red)

The Noble Gases• Elements in group 18• VERY unreactive,

monatomic gases• Do not combine with

other elements• Used in lighted “neon”

signs• Have a full valence

shell.

The Odd Ones

Hydrogen

• Hydrogen belongs to a family of its own.

• Hydrogen is a diatomic, reactive gas.

• Hydrogen is promising as an alternative fuel source for automobiles

Boron Family

• Elements in group 13• Aluminum metal was

once rare and expensive, not a “disposable metal.”

Carbon Family

• Elements in group 14• Contains elements

important to life and computers.

• Carbon is the basis for an entire branch of chemistry.

• Silicon and Germanium are important semiconductors.

Nitrogen Family

• Elements in group 15• Nitrogen makes up over ¾ of

the atmosphere.• Nitrogen and phosphorus are

both important in living things.

• Most of the world’s nitrogen is not available to living things.

• The red stuff on the tip of matches is phosphorus.

Metalloids

• Along the stair step line of the periodic table

• Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium

• Have characteristics of both metals and nonmetals

The periodic table is the most important tool in the chemist’s toolbox!

Metals, Nonmetals, and Metalloids

Metallic character increases down and to the left on the table and nonmetallic character

increases up and to the right on the table.

Atomic Radii Increase

Ato

mic

Rad

ii I

ncr

ease

Valence Electrons

• electrons available to be lost, gained, or shared in the formation of chemical compounds

• usually in the outermost s and p orbitals for main group elements (Families 1 & 2, and Families 13-18)

Valence Electrons for each group

• Group 1: valency +1

• Group 2: +2

• Group 3: +3

• Group 4: 4

• Group 5: -3

• Group 6: -2

• Group 7: -1

• Group 8: 0 stable. does not like to react with others.

• With each electron shell wanting to gain up to 8 electrons on outer shell

• An electron configuration shows the number of electrons in each orbital in a particular atom.

• Keep this in mind about the number of valence electrons and the Roman numeral column number: The IA family has 1 valence electron; the IIA family has 2 valence electrons; the VIIA family has 7 valence electrons; and the VIIIA family has 8 valence electrons. So for the families labeled with a Roman numeral and an A, the Roman numeral gives the number of valence electrons.

Neutral Atoms vs. Ions

• Cations – form positive ions by losing electrons (metals)

• Anions – form negative ions by gaining electrons (nonmetals)

Ionization Energy• Energy required to remove one electron

from a neutral atom of an element.• Increases left to right across the periodic

table.• Increases going from the bottom to the

top of a group.• For each successive electron in an atom

that is removed, the ionization energy increases.

Ionization Energies Increase

Electron Affinity• energy change that occurs when a neutral atom gains an

electron• Most atoms release energy when they acquire electrons.

Electronegativity• measure of an atom’s ability to attract electrons

in a chemical compound• If electron affinity is high, electronegativity will be

high.

Periodic Table

LanthanidesActinides

Alkaline Metals

Alkaline Earth Metals

Transition Metals

Noble Gases

Halogens

Metalloids

Group 15 pnictogensGroup 16 chalcogens

Group 13 boron familyGroup 14 carbon family

Metals, Nonmetals, and Metalloids

Metallic character increases down and to the left on the table and nonmetallic character increases up and to the right on the table.

Periodic Table w/ orbitals

Interactive Periodic Table

• http://center.acs.org/periodic/tools/PT.html