ATOMS, ELEMENTS & THE PERIODIC TABLE

PRE-PERIODIC TABLE CHEMISTRY… was a mess! No organization of elements. Imagine going to a grocery store with no organization. Difficult to find information. Chemistry didn’t make sense.

I AM DMITRI MENDELEEV! I made the PERIODIC TABLE !

HOW HIS WORKED… Put elements in rows by increasing atomic weight. Put elements in columns by the way they reacted. FUN FACTS He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) He broke the pattern of increasing atomic weight to keep similar reacting elements together. DMITRI MENDELEEV: FATHER OF THE TABLE

Families orGroups Periods

GROUPS OR FAMILIES… HERE’S WHERE THE PERIODIC TABLE GETS USEFUL! Elements in the same group or family have similar chemical and physical properties! (Mendeleev did that on purpose.)

FAMILIES ON THE PERIODIC TABLE Columns are families or groups. Families are typically one column. Families all have names. (Just like your family has a common last name.)

HYDROGEN Hydrogen belongs to a family of its own. Hydrogen is a highly reactive gas. Hydrogen was involved in the explosion of the Hindenberg.

ALKALI METALS 1 st column on the periodic table (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 Second column on the periodic table. 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 Elements in the center columns of the table Less reactive harder metals Includes metals used in jewelry and construction.

HALOGENS Elements in second to last family Very reactive nonmetals Always found combined with other element(s) in nature Used as disinfectants and to strengthen teeth

THE NOBLE GASES Elements in last family VERY unreactive gases Used in lighted “neon” signs

WHAT’S IN AN ATOM OF A GIVEN ELEMENT? An atom has three parts: Proton = positive (+) charge Neutron = no charge Electron = negative (-) charge

OPPOSITES ATTRACT Positive charges, such as protons, are attracted to negative charges, such as electrons (opposites attract) Like charges repel (positive charges repel other positive charges, and negative charges repel other negative charges)

WHAT’S IN AN ATOM? The protons & neutrons are found in the center of the atom in the nucleus. The electrons orbit the nucleus.

WHAT IS THE ATOMIC NUMBER? The number of protons found in the nucleus of an atom oror The number of electrons surrounding the nucleus of a neutral atom.

WHAT IS THE ATOMIC NUMBER? The atomic number is unique to that element. No two elements have the same atomic number.

KEY TO THE PERIODIC TABLE Elements are organized on the table according to their atomic number, usually found near the top of the square.

WHAT IS THE MASS NUMBER? The number of protons and neutrons in the nucleus of an atom. THIS IS NOT ON THE PERIODIC TABLE! MASS NUMBER IS NOT ATOMIC MASS/WEIGHT!

FOR ALL NEUTRAL ATOMS… # of PROTONS = ATOMIC # # of ELECTRONS = ATOMIC # # of NEUTRONS = MASS # – ATOMIC #