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الثلاثاء، 26 مارس، 2013

كيمياء لغات - الباب الأول| The principles[modifications ] of modern atomic theory


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كيمياء لغات - الباب الأول| The principles[modifications ] of modern atomic theory


01 The Principles Of Modern Atomic Theory



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كيمياء لغات - الباب الأول| The principles[modifications ] of modern atomic theory
The principles[modifications ] of modern atomic theory
* modern atomic theory based on some essential modifications on Bohr's model . the most important modifications are :- [exam 2007]
1) Dual nature of electron. (De Broglie)
2) Uncertainty principle. (Heisenberg)
3) Finding the mathematical expression which describes the wave motion of electron, its shape and energy. (schrodanger)
1- The dual nature of electron
Def *Electron is a particle has a wave properties.
* Every moving body such as electron, nucleus of an atom or all molecules or tennis ball is associated with a wave motion called “matter waves”.
* The matter waves differs from electromagnetic waves in two points.
1) They are not separating from the moving body.
2) Their speed doesn’t equal the speed of electromagnetic waves.
*Compare between matter waves and electromagnetic waves.
2) Heisenberg uncertainty principle [probability]
He proved that by using quantum mechanics
“It’s impossible to determine both of the location and the speed of electron
partically at the same time.”
* Because the apparatus used will change either speed or location of
the electron.
3) Schrodinger's wave equation
* He depended on planck , Einestein , De Broglie and Heisenberg to put the
wave equation
By solving this equation: -
* It can be used to determine the allowed energy levels of the electron.
*It can be used to define the region of space around the nucleus where it’s most probable to find the electron in each energy level.
As the result of this equation.
a) Our concept of the orbit around the nucleus changed to use the term orbital vail (electron cloud) to describe orbital.
b) By mathematical solution of schrodinger equation quantum numbers are introduced.
Orbit concept in Bohr’s theory Orbital concept in schrodinger’s wave mechanics concept.
• It’s a stable circular orbit of particular radii in which the electron orbits.
* It’s the region of space around the nucleus in which great prabability finding electron and the electron cloud is used to describe any orbital
*Compare between orbit and orbital [ def and draw ]
[ draw energy graph of orbit and orbital ] [ Exam 2006 ]
Orbital : - It’s the region of space around the nucleus with a great probability Electron cloud of finding the electron.
* Presence of electron in all directionsa and dimentions around
nucleus
2-THE FOUR QUANTUM NUMBERS”
Def: - These are numbers, which define the volume [ maximum prbability for finding electron ] beside shape, energy, and direction of orbitals in an atom.
1) Principal quantum number (n) its values 1,2,3,4,…not zero
K , L , M , N , O , P , Q
n = 1 2 3 4 5 6 7
Def a- It is a quantum number which determine the order of principal energy
levels of the electron [ seven in the known heaviest atom in ground state ]
b- determine the number of electrons, which fill each
main energy level according to the rule
2n2 [ twice square the principal quantum number ]
G.R.F * The rule 2n2 can’t be applied on the energy levels higher than fourth
Because: - The atom becomes unstable if the number of electrons
exceeds 32 in any energy level.
G.R.F * The third energy level ( M ) is saturated with 18 electrons
Due to the rule 2n2 which determine the maximum number of electrons
* Each principal energy level is subdivided into a number of sublevels which defined by value of another quantum number called subsidiary Q.number
*Bohr had used the P.Q.n to explain the spectral line of hydrogen atom.
2)Subsidiary(orbital or azimuthal)quantum number (l)
Def: - * It is a quantum number which define the number of energy sublevels in each principal energy level.it is equals P.Q.N
“Each principal energy level contains energy sublevels equal its number”
* These sublevels take the symbols as follow.
Main energy level (N) No. of sublevels Type of sublevels No. of orbitals (n2) No. of electrons (2n2)
K
1 1S 1 2
L
2 2S
2P 4 8
M
3 3S
3P
3d 9 18
N
4 4S
4P
4d
4F 16 32
* Observation: - This is shown by the scientist Sommerfield when he used a spectroscope, which has a high resolving power than Bohr .
* He found that: - [The single spectral line has divided into number of fine spectral lines]so “main energy levels contains energy sublevels equal its number
3) Magnetic quantum number (m) [2L+1]
Def :- It is a quantum number which defines the number of orbitals in
each sublevel.
*Each sublevel contains odd number of orbitals.
*Each orbital is saturated with 2 electrons.
*Orbitals of the same sublevel are similar in shape , energy , size but
different in direction
* S has (one) orbital (spherical symmetrical shape around the nucleus)
*P has (three) orbitals ( Px , Py , Pz )( filled with six electrons)
* d has (five) orbitals (So it is filled with ten electrons) G.R.F
*F has (seven) orbitals (So it is filled with 14 electrons) G.R.F
* It has spherical symmetrical shape around the nucleus. * Each P orbital is perpendicular to each other .
* The electron cloud of each orbital takes the forming of two pears meeting head to head
at point called node has no electron density.
[dumb-bell shape ]
Draw the shapes of
S and P orbitals P
Px Py Pz
4) The spin quantum no. (ms)
Def :- It is a quantum number which defines the spin motion of electron around its
axis during its rotation around the nucleus.
* The electron can rotate around its axis in either a clockwise or anti-clockwise
Although the two electrons of the same orbital carry the same negative charge,
they don’t repel. G.R.F
Because one of them rotates clockwise and other rotates anticlockwise So
The magnetic field of one electron is opposite to the magnetic field of other.
* it is said that the two electrons are in a spin paired state
G.R.F d- sublevel is filled with ten electrons but f-sublevel is filled with 14 electrons
……………………………………………………………………………………….
………………………………………………………………………………….
principles of distributing electrons
Aufbau (building-up) principle Hund’s rule
1) Aufbau (building-up) principle: -
“Electrons occupy the sublevels in the order of increasing their energy" [ The lowest energy sublevels are filled first” ]
* The sequence of energy sublevels according to their increasing energy follows this order: -
* Write the electronic configuration of the following atoms: -
11Na , 20Ca , 30Zn , 27Co , 35Br , 48Cd
11Na : 1S2 , 2S2 , 2P6 , 3S1
20Ca : 1S2 , 2S2 , 2P6 , 3S1 , 3P6 , 4S2
30Zn : 1S2 , 2S2 , 2P6 , 3S2 , 3P6 , 4S2 , 3d10
2) Hund’s rule: - “No electron pairing takes place in a given sublevel until
each orbital contains one electron” G.R.F.
*Because on pairing electrons the repulsion force produced decreases the stability of of the atom So electrons prefere to be a single before pairing.
7N 1S2 , 2S2 , 2P3 7N 1S2 , 2S2 , 2P3
(Wrong configuration)
* In the oxygen atom (its electron configuration is shown in this diagram) we find that sublevel 2P has (4) electrons.
* Three of them are distributed first in the three orbitals according to Hund’s rule.
G.R.F 1- 4S sublevel is filled before 3d
*Because 4S sublevel less energy than 3d and according to building up priciple ………………...
2- Electrons prefer pairing in the same sublevel than
transfer to higher energy level.
*Because energy of pairing less than energy of transfer to higher energy level
write electronic configuration according to
1- principal energy levels 2- Building up principal
3- Hund's rule 4- The nearest inert gas.
6C , 13Al , 16S , 7N , 26 Fe , 17Cl , 1H , 35Br
The relation between principal Q.N , sublevels and orbitals
1- Number of sublevels equals the principal quantum number [n]
2- Number of orbitals in the same level equals square the pricipal quantum number.[n2]
Ex . Second level consists of four orbitals [ 2S , 2Px , 2Py and 2Pz ]
3- Number of electrons which fill each main energy level equals twice squar the
principal quantum number [ 2n2 ]
Ex Second level filled with 8 electrons distributed as follow
[ 2S2 , 2Px2 , 2Py2 and 2Pz2 ]
Complete the following table
Main level Principal Q.N Sublevels Orbitals Electrons
First K
Second L
Third M
Fourth N
Write electronic configuration then determine sublevels and orbitals
12Mg , 21Sc , 16S , 8O , 28 Ni , 19K , 1H , 25Mn
…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
1-Sublevel (P) is saturated with (6)electrons.
2-Electrons never fall inside the nucleus.
3-Electrons occupy the sublevel (4S) before (3d).
4-The line spectra of any element is a property distinguish it.
5-Electrons prefer to be paired in the same Sublevel than transfer to higher energy level.
6-The electronic configuration of 8O is 1S2,2S2,2P4 but not 1S2,2S2,2P3,3S1.
7-Electrons of the same sublevel prefer to be single before pairing.
8-Electron has a Dual nature .
9-It’s impossible to determine both location and speed of electron at the same time.
10-Electron cloud is prefered to describe any orbital.
11-Atom has a vast space.
12-The electronic configuration of 2He is 1S2 but not 1S1,2S1.
13-Importance of solving Schrodinger’s equation.
14-Atom is electrically neutral.
15-Mass of the atom is concentrated inside the nucleus.
16-Quantum of energy required to transfer an electron from one energy level to another is not equal.
17-The rule 2n2 is not applied on the levels more than fourth.
18-Electrons doesn’t move from energy level to another if the energy absorbed
or emitted is less than quantum.
19-Sublevel (F)is saturated with (14)electrons.
20-Sublevel (d)is saturated with (10)electrons.
21-Sublevel (S)is saturated with (2)electrons.
1-Quantum:
2-Electron cloud:
3-Quantum numbers:
4-Principal Q.N:
5-Subsidary Q.N:
6-Magnetic Q.N:
7-Spin Q.N:
8-Exited atom:
9-Uncertainty principle
10-Auf-bau principle:
11-Hund’s rule:
12-De-Broglie princple:
13-Matter waves:
14-Node
1-Number of orbitals in sublevel (3d) is…………….. May95;96 Aug97
2-Energy sublevel that consistes of three orbitals is ……… Aug 95
3-The number of electrons required to fill the fourth energy level(N)….. May96
4- number of orbitals in the main energy level (n)is equal to …… May92
5-………..quantum number determines the number of the electrons in any energy level. May 91.
1-Pairing of electrons is not happened in an energy sublevel unless all the single electrons occupied the empty orbitals first.( ) May95;98
2-Numbers that define the shape and directions of the orbitals in the space. ( ) Aug 95
3-Quantum number that defines the orbitals of a given energy sublevel and their orientation in space ( ) May 98
1-Aufbau principle May 96
2-Hund’s rule May 97
3-Quantum May 94
1-(S) sublevel is saturated with (2)electrons while (P) sublevel is saturated with (6) electrons. Aug 98
2- Electrons prefere to occupy alone one orbital before pairing can takes place in a given sublevel. Aug 98
Notes :.
1- Difference in energy between main energy levels is large.
2- Difference in energy between sublevels in the same orbital is small.
3-There is no diff in energy between orbitals of the same energy levels.
1- principal quantum number and subsidary quantum number
2- Spin quantum number and magnetic quantum number
3- Matter waves and electromagnetic waves.
1- The electron has a dual nature in the sense that it is a ……… which also has ………..
2- The exciteed atom which gained ……… and then one ………. or more is transferred from its energy level to …………
3- The maximum number of energy levels in the known atoms in their ground stase is ……….
4- The sublevel (S) saturated with ………. electrons while the sublevel (d) is saturated with ……….. electrons
5- Sublevel (f) consists of ……… orbitals
6- The fourth energy level is saturated with ……… electrons while the second energy level is saturated with ………. electrons
7- Matter waves differ from electromagnetic waves in ……… and ……….
8- ……….. defines the subleveles and its number within a principal
energy level
9- Electrons rotate around the nucleus in a ………. movment. two forces affect the electron during its rotation which are ……… force and …………force
10-An element with atomic number 19, its electrons can be distributed in a
number of sublevels equals ……… and a number of orbitals
equals …………
11-In 3d7 , 3means ……… , d means ………. and 7 means …………
12-Any sublevel contains an odd number of …………
1-The maximum number of electrons occupying an energy level of a
principal quantum number (n) is ………..
a)2n b) n2 c)2n2 d) (2n)2
2-The number of orbitals in the 3d sublevel is ……….
a) Three b) Five c) six d) seven
3-The energy of the main energy level (N) is ………. The energy of the
main energy level (m).
a) greter than b) less than c) equal
a) 4-The sublevel (S) ………… a) has onlt one orbital c ) a and b
b) its shape is spherical and symmetrical.
5-The atom is ………. In the ground state .
a) Electrically neutral b) Negativity charged c) Positivly charged
6-The number of energy sublevels for an element of atomic number 18
equals…………. a) 3 b) 10 c) 6 d) 5
7-The number of sublevels equals ……….
a) n b) 2n c) n2 d) 2n2
8-The scintict who introduced the presence of sublevels is ………..
a) Hund b) Bohr c) Heisenberg d) schrodinger
9-If the atom was in its ground state, the electrons…………
a) lose energy b) Gain energy
c) Emit light continously d) don’t lose or gain energy.
10-Anyu orbital can be saturated with ………… electrons.
a) 2 b) 5 c) 18 d) 32
11-The number of orbitals in the (p) sublevel is …………..
a) Three b) four c) five d) severn
12-The sublevel energy that consistsa of three orbitals is ……….
( s , p , d , f )
13- The sublevel energy that consists of seven orbitals …………
( s , p , d , f )
14-The sublevel energy that consists of one orbital is ……….
( s , p , d , f )
15-The energy of orbitals are equal in one the following cases:-
a) Orbitals of 1s = 2s = 3s = 4s b) Orbitals of the same sublevel.
b) Orbitals of the same principal energy level.
c) Orbitals which contain the same number of electrons.
16-The third energy l;evel is saturated with ………….. electrons
( 8 – 10 – 18 – 32 )
17-The fourth energy level is saturated with ……….. electrons
( 8 – 18 – 32 )
18-The number of sublevel equals ………….
a) The principal quntum number .b) Squar the principal quantum number.
b) Three times the principal quanyum number.
19-the second energy level is saturated with ……….
(8 – 10 – 18 – 32 )
20-The number which indicates the number of sublvels in each principal
energy level is known as………..
a) The principal quantum numner. B) The subsiadary quantum number.
b) The spin quantum number.
21- The scientist who used the term orbital to indentify regions of space
around the nucleus in which the electron most probable excists is …….
( Hund – Heisenberg – Boher – Schrodinger )
Write the scietific term:
1-The region of space around the nucleus where there is a great probability
of finding the elctron. […………………..]
2-Every morning body is associated with a wave motion which has some
properties of light waves. [……………………..]
3-The number which describes the spin motion of an electron around its
own axis. […………………….]
4-The amount of energy absorbed or emitted when an electron is transferred
from one energy level to another. [………………….]
5-The atom which gained an amount of energy enough to transfer
electrons from their original level to higher ones. […………….]
6-Eletrons occupy orbitals in the order of increasing orbital energy, the
lwoest energy orbitals are filled first. [………………………..]
7-Number that defines the shapes and the direction of the orbitals in the
space. […………………………….]
8-Number that defines the principal energy levels in the atoms.[…………]
9-No electron pairing takes place in a given sublevel until each orbital contains one electron. […………………]
10-It is impossible to determine the location and the velocity of the
electron at the same time. [……………………]
11-The sublevel which consists of 5 orbitals.[……………….]
12-The wave that asocites any moving particle such as electron.
Secondly: Write the electronic configuration of each of the following
elements according to the Aufbau priciple:
10Ne , 15P , 19K , 26Fe , 30Zn
Choose form column (B) what suits to column (A)
(A) (B)
1-No electron pairing takes place in a given sublevel until each orbital contains one electron.
2-The atom is not uniformly dense and there is a
fast space in it.
3-It is impossible to determine the location of electron and its velocity practically at the same time.
4-The difference in energy between the principal energy levels is not equal, therefore each energy level has its own energy.
5-Electrons occuy the orbitals in the order of increasing orbital’s energy where the lowest levels are filled first.
6-Every moving body is associated with a wave motion. 1-Rutherford.
2-Bohr.
3-Heisenbergy.
4-Hund.
5-DeBroglie.
6-Aufbau.


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