Transcript ELECTRONIC CONFIGURATION OF ATOMS

Copyright Sautter 2003
ELECTRONIC CONFIGURATION OF ATOMS
USING ENERGY LEVEL DIAGRAMS
FOR
ATOMS
&
IONS
WHAT IS AN ELECTRONIC CONFIGURATION?
• ELECTRONIC CONFIGURATIONS SHOW THE
ENERGY STATES (ARRANGEMENTS) OF
ELECTRONS WITHIN DIFFERENT ATOMS
• FOR EXAMPLE WE CAN DETERMINE FROM THE
PERIODIC TABLE THAT HYDROGEN ATOMS
(ATOMIC NUMBER =1) HAVE BUT ONE ELECTRON
WHILE OXYGEN (ATOMIC NUMBER = 8) HAS
EIGHT ELECTRONS, BUT HOW ARE THEY
ARRANGED WITH EACH ATOM?
DETERMINING ELECTRON CONFIGURATIONS
• IN ORDER WRITE A CORRECT CONFIGURATION
FOR AN ATOM WE MUST:
• (1) FIND THE NUMBER OF ELECTRONS THE ATOM
CONTAINS
• (2) USE THE ENERGY LEVEL DIAGRAM TO
DETERMINE THE ORBITIAL LOCATIONS OF THE
ELECTRONS
• (3) PLACE THE ELECTRONS IN THE PROPER
ORBITALS USING TWO FUNDAMENTAL RULES
(THE PAULI EXCLUSION PRINCIPLE AND HUND’S
RULE)
ORDER
OF
ENERGY
LEVEL
FILLING
DETERMINING ELECTRON CONFIGURATIONS
(CONT’D)
• THE PAULI EXCLUSION PRINCIPLE STATES
THAT A MAXIMUM OF TWO ELECTRONS
(EACH WITH OPPOSITE SPINS) MAY OCCUPY
AN ORBITAL
• HUND’S RULE STATES THAT ORBITALS OF
EQUAL ENERGY MUST BE FILLED WITH
ELECTRONS ONE AT A TIME UNTIL ALL OF THE
ORBITALS ARE HALF FILLED, THEN FILLING
MAY BE COMPLETED RESULTING IN EACH
ORBITAL CONTAINING TWO ELECTRONS
MAXIMUM
DETERMINING ELECTRONCONFIGURATIONS
(CONT’D)
• ELECTRONS ARE ADDED TO THE ENERGY
LEVEL DIAGRAM ACCORDING TO THE
RULES PREVIOUSLY OUTLINED USING AN
ARROW TO REPRESENT EACH ELECTRON.
• EACH ORBITAL MAY CONTAIN A
MAXIMUM OF TWO ARROWS, ONE
POINTED UPWARD AND ONE POINTED
DOWNWARD TO SHOW THE OPPOSITE
SPINS OF THE PAIRED ELECTRONS.
• NOW LET’S SHOW THE ELECTRON
CONFIGURATION FOR THE HYDROGEN
ATOM.
Number of
Electrons in
the Orbital
Electronic
Configuration
For
Hydrogen
(1 electron)
Orbital
Type
Energy Level
Number
DESCRIBING ELECTRON CONFIGURATIONS
OF ATOMS
• ELECTRON CONFIGURATIONS MAY BE REPRESENTED IN
WRITTEN FORM OR DIAGRAMATIC FORM.
• IN WRITTEN FORM, THE ENERGY LEVEL NUMBER IS
WRITTEN FIRST FOLLOWED BY THE ORBITAL
DESIGNATION AND FINALLY THE NUMBER OF
ELECTRONS PRESENT IN THE ORBITAL IS SHOWN AS A
SUPERSCRIPT.
• FOR EXAMPLE, SODUIUM Na WITH 11 ELECTRONS
WOULD BE WRITTEN AS
1s2 2s2 2p6 3s1
• IN THE 1S2 TERM THE NUMBER 1 STANDS FOR THE
ENERGY LEVEL, S FOR THE ORBITAL TYPE AND THE
SUPERSCRIPT 2 MEANS TWO ELECTRONS ARE PRESENT
DESCRIBING ELECTRON CONFIGURATIONS OF
ATOMS (CONT’D)
• A COMMONLY USED ABBREVIATION IN WRITING
CONFIGURATIONS RECOGNIZES THAT ONCE AN ENERGY
LEVEL HAS BEEN FILLED AND INERT GAS
CONFIGURATION HAS BEEN CREATED. FOR EXAMPLE
ENERGY LEVEL 1 BEING COMPLETED GIVES A
CONFIGURATION FOR He, COMPLETION OF ENERGY
LEVEL 2 GIVES Ne, ENERGY LEVEL 3 GIVES Ar, ETC.
• AGAIN ASSUMING Na, 1s2 2s2 2p6 3s1, THE FIRST 10
ELECTRONS (1s2 2s2 2p6) LOOK JUST LIKE NEON AND
THEREFORE THE CONFIGURATION FOR SODIUM CAN BE
ABBREVIATED AS [Ne] 3s1 WHERE [Ne] = 1s2 2s2 2p6.
DESCRIBING ELECTRON CONFIGURATIONS
OF ATOMS (CONT’D)
• WRITING ELECTRON CONFIGURATIONS USING
THE DIAGRAMATIC METHOD REQUIRES
DRAWING A BOX OR CIRCLE TO FOR EACH
ORBITAL AND THEN FILLING IN ARROWS
REPRESENTING EACH ELECTRON PRESENT IN
EACH ORBITAL.
6 ELECTRONS
1s2 2s2 2p2
USING THE ENERGY LEVEL DIAGRAM
FOR HYDROGEN
3px
3py 3pz
2px
2py 2pz
3s
2s
1 ELECTRON
1s1
1s
USING THE ENERGY LEVEL DIAGRAM
FOR OXYGEN
3px
3py 3pz
2px
2py 2pz
3s
2s
8 ELECTRONS
1s2 2s2 2p4
1s
USING THE ENERGY LEVEL DIAGRAM
FOR TRANSITATIONAL ELEMENTS
3d
4s
3p
3s
* NOTICE 4s ORBITALS FILL
BEFORE 3D ORBITALS !!
2p
27 ELECTRONS
2s
1s
1s2 2s2 2p6 3s23p6
4s2 3d7
ELECTRONIC CONFIGURATIONS OF IONS
• WHAT IS AN ION ?
• A CHARGED ATOM OR GROUP OF ATOMS.
• HOW ARE IONS FORMED?
• BY GAINING OR LOSING ELECTRONS.
• WHAT ARE THE TWO KINDS OF POSSIBLE IONS ?
• POSITIVE IONS (CATIONS) AND NEGATIVE IONS (ANIONS)
• HOW ARE CATIONS AND ANIONS FORMED ?
• CATIONS ARE FORMED WHEN ATOMS LOSE ELECTRONS
AND ANIONS ARE FORMED WHEN ATOMS GAIN
ELECTRONS (PROTON NUMBERS NEVER CHANGE !)
ELECTRONIC CONFIGURATIONS OF
IONS (CONT’D)
• WHAT TYPES OF ATOMS GENERALLY FORM CATIONS AND
ANIONS ?
• CATIONS ARE GENERALLY FORMED BY METALS AND
ANIONS ARE GENERALLY FORMED BY NONMETALS
• HOW CAN THE NUMBER OF ELECTRONS IN AN ION BE
DETERMINED?
• FOR CATIONS, FIRST DETERMINE THE ATOMIC NUMBER OF
THE ATOM. THIS IS THE NUMBER OF ELECTRONS IN A
NEUTRAL (UNCHARGED) ATOM. SUBTRACT THE VALUE OF
THE POSITVE CHARGE ON THE ION FROM THE ATOMIC
NUMBER. THIS IS THE NUMBER OF ELECTRONS IN THE
CATION.
• FOR ANIONS, FIND THE ATOMIC NUMBER AND ADD THE
VALUE OF THE CHARGE ON THE ION. THIS IS THE NUMBER
OF ELECTRONS IN THE ANION.
ELECTRONIC CONFIGURATIONS OF
IONS (CONT’D)
• HOW MANY ELECTRONS ARE CONTAINED IN THE
CATION, Mg+2 ?
• THE ATOMIC NUMBER OF MAGNESIUM IS 12. THIS
MEANS THAT IT HAS 12 ELECTRONS IN THE
NEUTRAL MAGNESIUM ATOM. THE ION
THEREFORE HAS (12 – 2) OR 10 ELECTRONS.
• HOW MANY ELECTRONS ARE CONTAINED IN THE
ANION, N –3 ?
• THE ATOMIC NUMBER OF NITROGEN IS 7. THIS
MEANS THAT IT HAS 7 ELECTRONS IN THE
NEUTRAL NITROGEN ATOM. THE ION THEREFORE
HAS (7 + 3) OR 10 ELECTRONS.
ELECTRONIC CONFIGURATIONS OF
IONS (CONT’D)
• BOTH THE MAGNESIUM CATION (Mg+2) AND THE
THE NITRIDE ANION ION (N –3 ) HAVE THE SAME
NUMBER OF ELECTRONS. THESE IONS ARE SAID
TO BE “ISOELECTRONIC” WITH EACHOTHER
AND WITH THE NEAREST INERT GAS NEON
(ATOMIC NUMBER = 10)
• GENERALLY, ATOMS FORM CATIONS AND ANIONS
IN ORDER TO BECOME ISOELECTRONIC WITH THE
NEAREST INERT GAS. IN DOING THIS ATOMS
ACHIEVE COMPLETED OUTER ENERGY LEVELS
AND THIS RESULTS IN GREATER CHEMICAL
STABILITY !
ELECTRONIC CONFIGURATIONS OF
IONS (CONT’D)
• SOME ISOELECTRONIC ATOMS AND IONS
• NAME SOME IONS THAT ARE ISOELECTRONIC
WITH NEON (Ne) ?
• N-3, O-2, F-1, Na+1, Mg+2, Al+3
• NAME SOME IONS THAT ARE ISOELECTRONIC
WITH ARGON (Ar) ?
• P-3, S-2, Cl-1, K+1, Ca+2
ELECTRON CONFIGURATION FOR
IONS ISOELECTRONIC WITH NEON
N-3, O-2, F-1, Na+1, Mg+2, Al+3
2p
THE SECOND
ENERGY LEVEL
IS COMPLETED
2s
1s2 2s2 2p6
1s
ELECTRON CONFIGURATION FOR
IONS ISOELECTRONIC WITH ARGON
P-3, S-2, Cl-1, K+1, Ca+2
3p
3s
2p
THE THIRD
ENERGY LEVEL
IS COMPLETED
2s
1s2 2s2 2p6 3s23p6
1s