The Periodic Table

Why is the Periodic Table important to me? Its a useful tool You can use it on your tests. It organizes lots of data about elements. It lets you predict what type of bonds will form It lets you predict what type of ion will form

Dmitri Mendeleev

Dimitri Mendeleev (1869) Chemistry Professor Wrote the first Chemistry Book While organizing elements into chapters… Saw patterns in their chemical properties that matched their physical properties Used these paterns to create the Periodic Table of elements (56 of them at the time)

Mendeleev’s Periodic Law "the physical and chemical properties of the elements are periodic function of their atomic masses". Periodic = repeating Saw repeating patterns if elements were lined up by atomic mass

Mendeleev’s Table He put the elements in order of atomic mass When the patterns began to repeat he started a new row. Elements in each column had similar properties. He had to leave some blanks…said that undiscovered elements went there

SOME PROBLEMS… He broke the pattern of increasing atomic weight to keep similar reacting elements together. Not all elements seemed to fit his pattern

The Current Periodic Table Mendeleev wasn’t too far off. Now the elements are put in rows by increasing ATOMIC NUMBER!! The horizontal rows are called periods and are labeled from 1 to 7. The vertical columns are called groups are labeled from 1 to 18.

General Areas & Their Properties Metals Nonmetals Metalloids

Metals Shiny Malleable Ductile good conductors high melting points and boiling points usually solids

Nonmetals Not shiny Nonmalleable Not ductile Poor conductors Low melting and boiling points

Metalloids Elements that are not metals or nonmetals but have a mixture of both properties

Groups…Here’s Where the Periodic Table Gets Useful!! Elements in the same group have similar chemical and physical properties!! Why?? They have the same number of valence electrons. They will form the same kinds of ions.

Families on the Periodic Table Columns are also grouped into families. Families may be one column, or several columns put together. Families have names rather than numbers. (Just like your family has a common last name.)

Families

Hydrogen Hydrogen is its own family it is a diatomic, reactive gas Reacts quickly because it only needs to lose 1 electron to have a full outer shell Hydrogen caused the Hindenberg to explode Hydrogen is promising as an alternative fuel source for automobiles

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). React quickly bcs only need to lose 1 e- Soft enough to cut with a butter knife

Alkaline Earth Metals Second column on the periodic table. (Group 2) Reactive metals that are always combined with nonmetals in nature (react quickly - only need to lose 2 e-) important mineral nutrients Mg and Ca

Transition Metals Elements in groups 3-12 Less reactive harder metals used in jewelry and construction Metals used “as metal.” Have more than one oxidation # Lanthanide and Actinide Series are very radioactive!

Halogens Elements in group 17 Very reactive nonmetals (need to gain 1e-) Attract electrons VERY strongly Always combined with other element in nature. Diatomic = atoms come in pairs never alone Used as disinfectants and to strengthen teeth. Teflon = F bonded to C

The Noble Gases Elements in group 18 VERY un-reactive (inert) Used in lighted “neon” signs Used in blimps to fix the Hindenberg problem. Have a full outer electron shell so don’t need to react to get full outer shell

Ionization Energy vs Electronegativity How hard the protons in the nucleus pull on electrons Decreases as you get farther from the nucleus Coulombs Law says… Force of attraction = Charge e- * charge P distance2 How much energy it takes to remove outermost electron Further away from nucleus makes less force of attraction so Lower ionization energy

Atomic Radius Distance from the center of the nucleus to the outermost edge of the electron cloud

Periodic Trends This trend also tends to repeat as you go from one row to the next This is called periodicity, meaning the trend occurs in cycles Each horizontal row is called a period because it corresponds to one full cycle of a trend There are many properties that change gradually in moving from left to right across the table

Periodic Trends Radius decreases from left to right, increases as you move down a group

Atomic Size - Group trends H As we increase the atomic number (or go down a group). . . each atom has another energy level, so the atoms get bigger. Li Na K Rb

Atomic Size - Period Trends Going from left to right across a period, the size gets smaller. Electrons are in the same energy level. But, there is more nuclear charge. Outermost electrons are pulled closer. P S Cl Ar Si Na Mg Al

Trends in Electronegativity Electronegativity is the tendency for an atom to attract electrons to itself when it is chemically combined with another element. They share the electron, but how equally do they share it? An element with a big electronegativity means it pulls the electron towards itself strongly!

Electronegativity Group Trend The further down a group, the farther the electron is away from the nucleus, plus the more electrons an atom has. Thus, more willing to share. Low electronegativity.

The arrows indicate the trend: Ionization energy and Electronegativity INCREASE in these directions

Electronegativity Period Trend Metals are at the left of the table. They let their electrons go easily Thus, low electronegativity At the right end are the nonmetals. They want more electrons. Try to take them away from others High electronegativity.