ATOMS, ELEMENTS &

THE PE

RIODIC 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 FACTSHe 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 or

Groups

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.)

HYDROGENHydrogen belongs

to a family of its own.

Hydrogen is a highly reactive gas.

Hydrogen was involved in the explosion of the Hindenberg.

ALKALI METALS1st 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 METALSSecond 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 METALSElements in the center

columns of the tableLess reactive harder

metalsIncludes metals used

in jewelry and construction.

HALOGENSElements in second to

last familyVery reactive

nonmetalsAlways found

combined with other element(s) in nature

Used as disinfectants and to strengthen teeth

THE NOBLE GASESElements in last

familyVERY unreactive

gasesUsed in lighted

“neon” signs

WHAT’S IN AN ATOM OF A GIVEN ELEMENT?

An atom has three parts:Proton = positive (+)

chargeNeutron = no chargeElectron = 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

orThe 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 #