Transcript periodic table introduction

CHANCE FAVORS THE WELL PREPARED.
AS A RESULT OF STUDYING THE INTERACTION OF
LIGHT WITH GASEOUS ATOMS, SCIENTISTS CAME UP
WITH THE QUANTUM THEORY THAT DESCRIBES HOW
ELECTRONS ARE ARRANGED IN ATOMS.
QUANTUM THEORY TALKS ABOUT WHY ELECTRON
SHELLS AND SUBSHELLS FILL THE WAY THEY DO.
4 QUANTUM NUMBERS ARE USED TO DESCRIBE THE
PROBABLE POSITION OF ELECTRONS IN ATOMS.
NO TWO ELECTRONS CAN HAVE THE SAME 4 NUMBERS.
THE FIRST DESCRIBES THE SHELL.
THE SECOND DESCRIBES THE SUBSHELL.
THE THIRD BREAKS THE SUBSHELL DOWN INTO
ORBITALS.
THE FOURTH DESCRIBES THE ELECTRON SPIN.
WE ARE ONLY GOING TO BE CONCERNED WITH SHELLS
AND SUBSHELLS.
THE FIRST SHELL CAN ONLY HAVE ONE SUBSHELL, AND
THAT IS AN s SUBSHELL WHICH CAN HOLD ONLY 2
ELECTRONS.
THE SECOND SHELL CAN HAVE TWO SUBSHELLS – AN s
AND A p. A p SUBSHELL CAN HOLD 6 ELECTRONS.
THE THIRD SHELL CAN HAVE THREE SUBSHELLS – AN s,
A p, AND A d. A d SUBSHELL CAN HOLD 10 ELECTRONS.
FINALLY, ANY SHELL BEYOND THE THIRD CAN HAVE 4
SUBSHELLS – AN s, A p, A d, AND AN f (14 electrons).
THE FOLLOWING TABLE GIVES THE INFORMATION ON
THE SHELLS AND SUBSHELLS:
Principal
Quantum
Number
(shell)
Number of
Subshells
Type of Subshell
n=1
1
1s (2 electrons)
n=2
2
2s (2 electrons)
2p (6 electrons)
n=3
3
3s (2 electrons)
3p (6 electrons)
3d (10 electrons)
n=4
4
4s (2 electrons)
4p(6 electrons )
4d(10 electrons)
4f (14 electrons)
The first shell (n=1) can only hold 2 electrons,
so there are only 2 elements in the first
period.
The maximum number of electrons in an outer
shell other than the first is 8.
2 electrons in the first shell or 8 electrons in
any other outer shell represent a very stable
configuration. This is called the octet rule.
This will be very important when we talk about
chemical bonding.
Quantum theory talks about why electron shells
and subshells fill the way they do.
THE IDEA OF A PERIODIC TABLE WAS
DEVELOPED BY SEVERAL SCIENTISTS AT
ABOUT THE SAME TIME.
MENDELEEV WAS THE FIRST TO PUBLISH
IN 1869. HE SUGGESTED THAT SUCH A
TABLE COULD BE CONSTRUCTED BY
ARRANGING THE ELEMENTS IN ORDER OF
INCREASING ATOMIC MASS.
LATER, SCIENTISTS REALIZED THAT IT
SHOULD BE IN ORDER OF INCREASING
ATOMIC NUMBER.
PERIODIC LAW – WHEN ELEMENTS ARE
ARRANGED IN ORDER OF INCREASING
ATOMIC NUMBER, THERE IS A PERIODIC
REPETITION OF THEIR PHYSICAL AND
CHEMICAL PROPERTIES.
NOW, IN THE PERIODIC TABLE, THE
VERTICAL COLUMNS ARE CALLED FAMILIES
OR GROUPS.
THE HORIZONTAL ROWS ARE CALLED
PERIODS.
ALL OF THE ELEMENTS IN A GIVEN COLUMN
OR FAMILY WILL HAVE SIMILAR OUTER
ELECTRON CONFIGURATIONS. FOR EXAMPLE,
TAKE THE 1ST COLUMN – THE ALKALI METALS.
H – 1s1
Li – 2s1
Na – 3s1
K – 4s1
Rb – 5s1
Cs – 6s1
ALL HAVE 1 ELECTRON IN THE OUTER SHELL.
THE OUTER SHELL IS IMPORTANT.
IT IS THE ELECTRONS IN THE OUTERMOST
SHELL THAT WILL BE INVOLVED IN
CHEMICAL REACTIONS.
THEY ARE CALLED VALENCE ELECTRONS.
THEY WILL FORM CHEMICAL BONDS
THROUGH LOSS, GAIN, OR SHARING.
TAKE ANOTHER EXAMPLE – THE SECOND
COLUMN, THE ALKALINE EARTH METALS:
Be – 2s2
Mg – 3s2
Ca – 4s2
Sr – 5s2
Ba – 6s2
THEY ALL HAVE TWO ELECTRONS EACH IN
THEIR OUTER SHELLS.
OR, TAKE GROUP 7A, THE HALOGENS. THEY
ALL HAVE 7 ELECTRONS IN THE OUTER
SHELL.
F – 2s22p5
Cl – 3s23p5
Br – 4s24p5
I – 5s25p5
At – 6s26p5
THE GROUP NUMBER FOR THE A GROUP
ELEMENTS WILL TELL YOU HOW MANY
ELECTRONS ARE IN THE OUTER SHELL –
VALENCE ELECTRONS.
GROUP
NAME
ELEMENTS
1A
Alkali Metals
Li, Na, K, Rb, Cs,
Fr
2A
Alkaline Earth
Metals
Be, Mg, Ca, Sr,
Ba, Ra
7A
Halogens
F, Cl, Br, I, At
8A
Noble Gases
He, Ne, Ar, Kr,
Xe, Rn
THE ELEMENTS ARE GROUPED ACCORDING
TO ELEMENT TYPE AS WELL – METALS,
NONMETALS, AND METALLOIDS.
THE METALS TO THE LEFT OF THE
PERIODIC TABLE, STARTING WITH THE
LIGHT BLUE, DARK BLUE, BLUE-GRAY, AND
ORANGE.
THE NONMETALS ARE TO THE RIGHT OF
THE PERIODIC TABLE AND ARE GREEN,
YELLOW, AND ORANGE.
THE METALLOIDS ARE IN PURPLE.
METALS ARE ALL SOLIDS, WITH ONE
EXCEPTION (MERCURY), AT ROOM
TEMPERATURE.
THEY HAVE A SHINY SURFACE WHEN
FRESHLY CUT OR POLISHED.
THEY ARE GOOD CONDUCTORS OF HEAT
AND ELECTRICITY.
MOST CAN BE PULLED INTO WIRES
(DUCTILE) OR ROLLED INTO SHEETS
(MALEABLE).
NONMETALS ARE BRITTLE SOLIDS OR
GASES AT ROOM TEPMERATURE. BROMINE
IS THE ONLY LIQUID.
THEY ARE NOT GOOD CONDUCTORS OF
ELECTRICITY OR HEAT (WITH THE
EXCEPTION OF CARBON).
METALLOIDS HAVE PROPERTIES BETWEEN
THOSE OF METALS AND NONMETALS.
SILICON WOULD BE A GOOD EXAMPLE. IT
LOOKS LIKE A METAL, BUT IT IS BRITTLE.
THE ELEMENTS IN DARK BLUE IN THE
CENTER OF THE PERIODIC TABLE ARE
CALLED THE TRANSITION METALS.
AS YOU MOVE ACROSS A PERIOD,
ELECTRONS ARE BEING ADDED TO THE d
SUBSHELLS.
FOR EXAMPLE, STARTING WITH ELEMENT
21, SCANDIUM, AND MOVING ACROSS TO
ZINC, ELECTRONS WOULD BE ADDED TO THE
3d SUBSHELL.
IN THE LANTHANIDE SERIES (STARTING
WITH ELEMENT 58) ELECTRONS ARE
GOING INTO THE 4f SUBSHELL.
THE LANTHANIDE SERIES ELEMENTS ARE
SOMETIMES REFERRED TO AS THE RARE
EARTH ELEMENTS.
IN THE ACTINIDE SERIES (STARTING
WITH ELEMENT 90) ELECTRONS ARE
GOING INTO THE 5f SUBSHELL.