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كيمياء - Chapter ( 1 ) - Atomic structure

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14/01/2013 على 09:48 #2 بواسطة nezarmsm
chemistry : ch 1 - quantum number
أ / رشا عبد الوهاب ، أ / محمد عبد الله رياض
مدرسة على الهواء ، كيمياء لغات

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29/10/2011 على 21:12 - 29/10/2011 على 21:14 #3 بواسطة nezarmsm
Questions
By : M. Mohamed Abdallah Reyad
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Chapter-1

Questions ( 1 )
Choose the correct answer:
1- the first scientist who define the element is …..
a) Boyle
b) Rutherford
c) Bohr
d) Thmson

2- All matter composed of four component (water,air,dust and fire) is belong to …..
a) Bohr
b) Rutherford
c) Dalton
d) Aristotle

3- The strong evidence that proved that cathode rays exist in all matters ….
a) they have thermal effect.
b) flow in straight lines.
c) cosist of fine particles.
d) they have the same proerties whatever the type of gas or cathode.

4- The scientist who named cathode rays by electrons in 1897 is …..
a) Boyle
b) Rutherford
c) Bohr
d) Thomson

5- The uncertainty principle was found by …..
a) Bohr
b) De Broglie
c) Heisenberg
d) Schrodinger

6- s,p,d and f are symbls of …….
a) principle energy levels
b) energy sublevels
c) orbital of sublevels.
d) single electrons in orbitals

7- The quantum number which define the motion of the electron is the …
a) principle quantum number .
b) subsidiary quantum number.
c) magnetic quantum number.
d) spin principle quantum number.

8- Which configuration represents nitrogen according to Aufbau ……
a) 2,5
b) 1s2, 2s2, 2p3
c) 1s2 ,2s2 ,2px1 , 2py1 , 2pz1
d) 1s2, 2s1, 2p4

9- When a gas or vapour is heated at high pressure and very low pressure it ….
a) absorb energy.
b) emit light.
c) emit gamma radiation
d) emit alpha particle.

10- When an electron absorbs a quntum of energy it …
a) jumps to all higer energy levels
b) jumps to higher energy level corresponding to absorbed energy.
c) drops to all lower energy levels
d) drops to lower energy level corresponding to absorbed energy

11- The magnetic quantum number ( m) defines ….
a) the principle energy level
b) number of energy sublevels
c) number of orbital and their shape
d) number of electrons in the orbitals.

12- The number of orbitals in the sublevel 3d equals ……
a) four
b) five
c) six
d) seven

13- The number of orbitals in the principle energy level(n) equals ……
a) n
b) 2n
c) n2
d) 2n2

14- The maximum number of electrons in a given energy level (n) equals ……
a) n
b) 2n
c) n2
d) 2n2

15- Sublevels can be arranged according to their energies as follows …..
a) 1s<2s<3s<4s<2p<3p<3d
b) 1s<2s<2p<3p<3d<4s<4p
c) 2s<2p<2d<3s<3p<3d<4s
d) 1s<2s<2p<3s<3p<4s<3d

16- The orbital of the same energy level are …
a) equal in energy
b) different in energy
c) different in shape
d) similar in direction

17- One of these diagrams shows the distribution of oxygen atom

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18- When the electron returns from higher level to its original level it ….
a) loses a quantum energy
b) gains a quantum energy
c) absorbs radiations
d) absorbs light

19- When the electron gains energy less than quantum it …
a) transfer to higher energy level
b) remains in its level
c) transfer to lower energy level
d) leave the atom

20- From the modification of Bohr's theory ……
a) dual nature of the electron.
b) Schrodinger equation
c) uncertainty principle
d) all the previous

21- Scientist who discovered sublevel is …..
a) Rutherford
b) Bohr
c) Sommerfield
d) Schrodenger

22- Scientist who introduced principal quntum number is …..
a) Rutherford
b) Bohr
c) Sommerfield
d) Schrodenger

23- Element of atomic number 15 has number of orbitals equals ……..
a) 3
b) 5
c) 9
d) 15

24- Element of atomic number 21 has number of sublevels equals ……..
a) 4
b) 7
c) 9
d) 11

25- Element of atomic number 19 has number of energy levels equals ……..
a) 3
b) 4
c) 7
d) 8

26- Emanation (radiation) which which defected towards negative electrode is ….
a) beta particle
b) x-rays
c) alpha particle
d) gamma rays

27- All of the atoms of argon have the same
a) mass number
b)atomic number
c) number of neutrons
d) number of nucleons

28- All of the atoms of oxygen have the same except
a) mass number
b)atomic number
c) number of proton
d) number of electrons

29- When the excited electron returns to its original level it emits energy as …….
a) beta particles
b) alpha particles
c) spectral lines
d) gamma radiation

30- An element of atomic number 28 how many d orbitals have filled
a) 2
b) 3
c) 4
d) 5

31- The maximum number of electrons that occupy a single orbital of (3d) sublevel is….
a) 1
b) 2
c) 4
d) 5

32- In which sulevel would an electron have the lowest energy
a) 4s
b) 4p
c) 4d
d) 3d

33- In which sulevel would an electron have the highest energy
a) 3s
b) 3p
c) 3d
d) 4s

34- The total number of completely filled orbital in nitrogen atom is …..
a) 1
b) 2
c) 4
d) 5

35- At distribution of electrons , Hund's rule applied in ……
a) main levels
b) sublevels
c) main level orbital
d) sublevel orbital


Question ( 2 )

Write the scientific term :

1- The very small very dense of the atom .
2- Pur substance which cann't be divided by traditional chemical method.
3- The number of protons in the nucleus
4- The number of protons and neutrons in the nucleus.
5- Amount of energy needed to transfer the electron from one energy level to another.
6- Electrons occupy sublevel in rder of increasing their energy.
7- No pairing of electron takes place in a sublevel until each orbital contains one electron.
8- The number that define the main energy level.
9- The number that define the number of sublevel in a given energy level.
10- The number that define the number and shape of orbitals in a given sublevel.
11- The number that define the motion of the electron around its axis .
12- A stream of invisible rays emitted from a gas under low pressure and high volts.
13- The electron is a particle and it has wave properties.
14- It is impossible to determine the speed and the location of the electron at the same time
15- Region of space around the nucleus where the electron most proble exists.
16- An atom acquired energy enough to transfere the electron to higer energy level.
17- When an electrically charged particle moves in an orbit it will lose some ot its energy by emition radiation and its radius gradually decreases.


Question ( 3 )

What is meant by :

1- Element.
2- Cathode rays.
3- Electron cloud.
4- The dual nature of the electron.
5- Building up principle.
6- Heisenberg uncertainty principle.
7- Hund's rule.
8- Quantum.
9- The principle quantum number.
10- The subsidary quantum number.
11- The magnetic quantum number.
12- The spin quantum number.
13- The exited state of the atom.
14- The ground state of the atom.
15- Line spectrum.
16- Quantium numbers.
17- Maxwell's theory.


Question ( 4 )

Give reasons for:

1- The line spectra of any element is a specific.
2- The electron has a dual nature.
3- The atom is electrically neutral but nucleus is positive.
4- The atom is not uniformaly dense.
5- No electron pairing occurs untail each orbital takes one electron.
6- Sub level (s) saturated by 2 electrons .
7- Sublevel (p) saturated by 6 electrons .
8- Sub level (d) saturated by 10 electrons .
9- Sub level (f) saturated by 14 electrons .
10- Energy level (K)saturated by 2 electrons .
11- The mass of the atom is concentrated in the nucleus.
12-Energy level (L)saturated by 8 electrons .
13- Energy level (M)saturated by 18 electrons .
14- Energy level (N)saturated by 32 electrons .
15- Energy level (O)saturated by 32 electrons only.
16- The electron never fall in the nucleus.
17- Amount of energy needed to transfer electrons between energy levels not equal.
18- It is impossible to determine both speed and location of the electron at the same time
19-The rule 2n2 doesn't apply to enegy levels higher than the fourth level.
20 - Any orbital can't occupied by more than two electrons.
21- Although the 2 electrons in the same orbital have the same charges but they don't repel
22- The two electrons of the same orbital spin in opposite directions.
23- Electron pairs with another in the orbital rather entering vacant higher energy orbital
24- It is wrong to consider the electron is a negative particle only.
25- Sublevel 4s is filled by electrons before sublevel 3d.
26- Electrons preferred to occupy orbital independent before they paired.
27- When the electron occupies sublevel (p) it may be occupy px or py or pz
28- According to Bohr's theory we can determine the speed and the location of the electron.
29- Proerties of cathode easy are similar whatever the type of the cathode or the gas..
30- Most of alpha particle penetrate the gold sheet.
31- Few of alpha particle are reflected when they collide the gold sheet.
32- Few of alpha particle are deflected when they collide the gold sheet.
33- Single electrons in the same sublevel take the same direction.
34- Rutherford's model was contradicted by Maxwell's theoty.


Question ( 5 )

Explain each of the following :

1- The observation upon which Rutherford reached the following conclutions:
a) Most of the atom is empty space ( not a solid sphere )
b) There is a very dense tiny piece of the atom ( named nucleus)
c) The charge of the dense part of the atom is positive.
2- How the cathode rays may be obtained.
3- Dalton's atomic theory.
4- Thomson's atomic model.
5- The four quantum number of the atom.
6- Rutherford's experiment.
7- How could Bohr reconcilate betweem Ratherford's model and Maxwell's theory.



Question ( 6 )

Write the electronic configuration of these elements :

a) according to aufbau
b) according to Hund's rule
Boron (5)
- Nitrogen (7)
- Fluorine (9)
– Sulphur (16)


Question ( 7 )

Compare between :

1- Principle quantum number and subsidiary quantum number.
2- Magnetic quantum number and spin quantum number.
3- Matter waves and electromagnetic waves
4- Orbit of bohr and orbital of schrodinger.
5- Electron in ground state and electron in exited state.
6- Cathode rays and emission spectrum.
7- Sublevel s and sublevel p
8- Sublevel d and sublevel f


Question ( 8 )

What are :

1- The objection of Rutherford's atomic model.
2- The advantages of Bohr's atomic model.
3- The disadvantages of Bohr's atomic model.
4- The properties of cathode rays.


Question ( 9 )

Correct the under line words and give reasons:

1- Amount of energy needed to transfer electron from K to N equals 3 quantum.
2- It is possible to determine the speed and the location of the electron at the same time.
3- No. of electron that saturate fifth energy level equals 50 electrons.
4- Energy needed to transfer electrons between energy levels are equal .
5- In ground state of the atom the electron fall in the nucleus .
6- Charcters of cathode rays depend on the type of the gas in the cathode tube.
7- Cathode rays are deflected to the cathode .


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23/10/2011 على 21:42 - 23/10/2011 على 23:10 #4 بواسطة nezarmsm
By : M. Mohamed Abdallah Reyad

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Chapter ( 1 )
Atomic structure


1- Greek Philosopher :
- They imagined that : it is possible to divide the matter into smaller parts
- These parts can be divided into smaller particles and so on
- This go on until we reach individable fragments called atoms.

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2- Aristotle :
- He refused the concept of the atom.
- He believed that all matters are composed of four components which are:
" water, air, dust and fire"
- He believed that matters are different from each other in the ratio of these components
- So we can change cheap metals such as iron or copper into more precious ones such as gold

3-Boyle(1661) :

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- He refused the idea of Aristotle .
- He gave the first definition of the element as:
" A pure simple substance that cannot be devided into simpler forms by traditional chemical methods"

4- Dalton(1803) :

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- He put the first atomic theory.
Postulates of the Atomic Theory :
1- The mater is made of many small particles called atoms.
2- The atom is undividable solid part.
3- Atoms of an element are similar and different from atoms of another element.

Cathode rays
1- Gases don not conduct electricity under the normal temperature and pressure.
2- At low pressure 0.01 – 0.001 mmHg gases conduct electricity.
3- When the potential difference is about 10,000 volts a stream of invisible rays was emitted from
cathode which is called cathode rays.

Properties of cathode rays :
1- They consist of very fine particles.
2- They move in straight lines.
3- They have thermal effect.
4- They are negative charges.
5- They are affected by electric field and magnetic field.
6- They have the same properties whatever the type of cathode or the used gas.

5- Thomson( 1897) :

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The atomic model of Thomson :
- The atom is a sphere of a uniform positive electricity.
- Negatively charged electrons embedded in it.
- The atom electrically neutral because no. of positives charges = no. of negative charges.

6- Rutherford's atom(1911) :
Experiment of Geiger and Marsden

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Rutherford :
The first scientist who stated the concept of atomic structure.

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Postulates of Rutherford:
1)The atom:
-Very small.
b. Resembles solar system.
c. It is consisted of nucleus and electrons.

2)The nucleus:
-Very smaller .
-It is not uniformly dense.
-Vast space between the nucleus and the orbits of the electrons.
-Most of the atomic mass is concentrated in it.
- It contains positive protons and neutral neutrons.

3)The electrons:
-They have negligible mass.
-They are negative charges.
-The number of electrons equals the number of protons.
(So the atom is electrically neutral)
-The electrons orbit the nucleus in special orbits at high speed.
-The electron keeps its orbits due to two forces:
Attraction force and centrifugal force.
They are equal in quantity and oppose in direction.

Objections on Rutherford’s atomic model:
It was contradicted by Maxwell’s theory.

Maxwell’s theory:

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- It was based on Newtonian mechanics.
- It is concerned with the movement of relatively large bodies.
It states that:
“ When a charged particle moves in an orbit it will:
1) Loses some of its energy by emission of radiation.
2) Its radius gradually decreases.

Objection:
By applying this theory on the model of Rutherford : the electron must
Lose some of its energy by emission of radiation.
Its radius gradually decreases.
It will spiral inwards until it hits the nucleus.
This leads to end up the structure of the atomic system.
It doesn’t happen in nature.

7) Bohr’s atomic model:

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He adopted some of Rutherford’s postulates.
He added :
Electrons:
Each electron has a definite amount of energy
Electrons orbit the nucleus without losing or gaining energy.
Electrons orbit the nucleus in definite energy levels.
c. Electrons cannot be found in the distance between energy levels.

Energy levels:
The maximum number of energy levels in an atom = 7
Each energy level is designated by certain letter which are
K,L,M,N,O,P,Q
Each energy level is expressed by a principal quantum number.
The principal quantum number of the first level = 1
The principal quantum number of the second level = 2 (And so on)
The energy of the level increases as its radius increases.
Ground state of the atom:
When the electrons remain in the lowest allowed energy levels.
Excited state of the atom:
When the electron gains an amount of energy (equals quantum) it jumps to a higher energy level temporarily.
Then the electron returns to its original level losing this energy
in the form of radiation as a certain spectral line.
at the same time many atoms absorb different amounts of energy then radiate these energies as special spectral lines.

Quantum:
“ The amount of energy absorbed or emitted when an electron jumps from one energy level to another.”
The quantum of energy required to transfer the electron from one energy level to another is not equal.
there is no parts or doubles of quantum.

Bohr’s Atomic Model:
Succeeded in:
1- Explaining the spectrum of hydrogen atom.
2- Introducing the idea of quantized energy.
3- Reconciliation between Rutherford’smodel and Maxwell’s theory.
(When he said that the electron orbits without losing or gaining energy)
Inadequacy of the model:
1- It failed to explain the spectrum of any other element except hydrogen atom.
2- It considered the electron as a particle only but it also has wave properties.
3- It postulated that it is possible to determine precisely both the location and speed of an electron at the same time.
(Experimentally it is impossible because any used apparatus will change either the location or the speed)
4- It described the electron motion in a circular planer orbit, which means the atom is a planar but the atom has three-dimensional coordinates.

8) The principle of Modern Atomic Theory

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The most important modifications are:
1-The dual nature of the electron.( De Broglie)


“ The electron is a particle and also has wave properties. “
This wave is called “matter wave”

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2-The Heisenberg uncertainty principle:

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“ The determination of both the velocity and the position of an electron at the same time is practically impossible.”
We can only say, “the electron may be found in this or that place”

3-The wave equation: ” Schrodinger”

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Schrodinger derived a wave equation that could describe the electron wave motion and the allowed energy levels in the atom.

Orbital (electron cloud ):
“ The region of space around the nucleus in which the electron most probable exists”


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Quantum numbers:

They define the volume of space in which the electron most probable found.
(they are used to define main energy levels, sublevel and orbitals)
1) The principal quantum number ( n )
Bohr used this number to explain the spectrum of the atom
This number is used to define:
"The order of the main energy levels"
The number of electrons needed to saturate an energy level
Number of electrons = 2n2
The first energy level has principal quantum number = 1
The second energy level has principal quantum number = 2
And so on.

2) The subsidiary (azimuthal) quantum number ( l )
It indicates the number of energy sublevel in a given energy level .
Each energy level has a number of sublevel equal to its principal
quantum number ( up to four ).
The first energy level ( K ) has one sublevel ( 1s )
The second energy level ( L ) has two sublevel ( 2s,2p )
The third energy level ( M ) has three sublevel ( 3s,3p,3d )
The fourth energy level ( N ) has four sublevel ( 4s,4p,4d,4f )
The fifth energy level ( O ) has four sublevel ( 5s,5p,5d,5f )
Sommerfield discovered the energy sublevel using a high resolving
power spectroscope .
Sublevels are considered as the real energy levels
The energy sublevel takes the symbols ( s , p , d and f ) .
There is a small difference in the energy of the sublevels .
s < p < d < f

3) The magnetic quantum number ( m )
It represents the number,shape and direction of orbitals in a sublevel
The sublevel (s) has one orbital - spherical symmetrical around the nucleus.
The sublevel (p) has three orbitals- they are dumb-bell in shape.( the form
of two pears meeting head by head)-their axes take the three spatial orientation
(px ,py pz )-they are perpendicular to each other .
The sublevel (d) has five orbitals .
The sublevel (f) has seven orbitals .

4) The spin quantum number ( ms )
It represents the direction of the motion of the electron around its axis.
The motion may be : 1- Clockwise
2- Anticlockwise


The relation between :
Energy levels, sublevel, orbitals and electrons.
A given energy level ( n ) has:
Number of sublevel equals n
Number of orbitals equals n2
Number of electrons equals 2n2

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Principles of distributing electrons:
1) Aufbau ( building ) principle :
“ Electrons occupy the orbitals in the order of increasing orbital energy the lowest energy orbitals are filled first “
The sequence of energy sublevel
1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f <5d <6p <7s <5f <6d
Example :
Write the electronic configuration of these elements
26Fe = 1s2,2s2,2p6,3s2,3p6,4s2,3d6

2) Hund’s rule

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“ No electron pairing takes place in a given sublevel until each orbital contains one electron”
Example:
7N= 1s2 ,2s2 ,2px1 ,2py1 ,2pz1
Notes:
1- Orbitals of the same sublevel have the same energy,but different directions
2- Single electrons in a sublevel take the same direction to be more stable.
3- The electron preferred to paired with other electron than to transfer to higher sublevel because it needs higher to transfer to a higher sublevel but it needs less energy to overcome the repulsive force in the same orbital
4-The sublevel 4s is filled before 3d because it has less energy.

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