In olden time it is thought that iron can be converted into gold.

Because they thought that all materials are composed of water, air, dust and fire and by changing their ratio Fe can be changed into Au.

They are affected by electric and magnetic field. They are affected by electric and magnetic field.

They are negative charged particles. The type of gas or the material of cathode does not change their nature or behavior.

Negativlycharged electron electronNegativlycharged Ball of positive charge charge

Most α penetrate gold foil Most α penetrate gold foil Most α penetrate gold foil Most α penetrate gold foil Most of atom is space. Most of atom is space. Most of atom is space. Most of atom is space. Small ratio are Small ratio are reflected from gold foil. reflected from gold foil. Small ratio are Small ratio are reflected from gold foil. reflected from gold foil. Avery small dense part in the atom called “nucleus”. Avery small dense part in the atom called “nucleus”. Avery small dense part in the atom called “nucleus”. Avery small dense part in the atom called “nucleus”.

Small ratio are deflected from original position. Small ratio are deflected from original position. Small ratio are deflected from original position. Small ratio are deflected from original position. The nucleus is positive as alpha particles. The nucleus is positive as alpha particles. The nucleus is positive as alpha particles. The nucleus is positive as alpha particles.

Because the number of +ve protons = Number of - ve electrons. electron electron nucleusnucleus

When the element is heated its electrons gain energy and move from their original levels to energy levels far from nucleus, When the element is heated its electrons gain energy and move from their original levels to energy levels far from nucleus, When the element is heated its electrons gain energy and move from their original levels to energy levels far from nucleus, When the element is heated its electrons gain energy and move from their original levels to energy levels far from nucleus,

then they return to their original levels emitting this energy in form of light of definite wavelength forming emission spectrum. then they return to their original levels emitting this energy in form of light of definite wavelength forming emission spectrum. then they return to their original levels emitting this energy in form of light of definite wavelength forming emission spectrum. then they return to their original levels emitting this energy in form of light of definite wavelength forming emission spectrum.

Atom where electrons are in their original energy levels. Atom in a lower energy state.

Atom where electrons are in a higher energy levels. Atom where electrons are in a higher energy levels. Atom where electrons are in a higher energy levels. Atom where electrons are in a higher energy levels. Atom in a higher energy state. Atom in a higher energy state. Atom in a higher energy state. Atom in a higher energy state.

“Is the key for explaining the atomic structure”. “Is the key for explaining the atomic structure”.

It is the radiation produced on returning electrons from higher energy levels to their original energy levels." It is the radiation produced on returning electrons from higher energy levels to their original energy levels." It is the radiation produced on returning electrons from higher energy levels to their original energy levels." It is the radiation produced on returning electrons from higher energy levels to their original energy levels."

Because elements have different number of electrons, so differ in the radiation produced on returning

the electrons from higher energy levels to their original energy level.

Because when the electrons lose energy in the excited state, they return from different higher energy level to

their original level, where the energy is lost in form of radiations of definite wavelengths. in form of radiations of definite wavelengths. their original level, where the energy is lost in form of radiations of definite wavelengths. in form of radiations of definite wavelengths.

Because its electron returns from different higher energy level to its original level Because its electron returns from different higher energy level to its original level

losing its energy in form losing its energy in form of radiation of definite wavelengths. of radiation of definite wavelengths. losing its energy in form losing its energy in form of radiation of definite wavelengths. of radiation of definite wavelengths.

“Hydrogen and helium ” are the main components of the sun. “Hydrogen and helium ” are the main components of the sun.

Enables Bohr to reach his atomic model.

A positively charged nucleus exists in the center of the atom where electrons rotate around it. A positively charged nucleus exists in the center of the atom where electrons rotate around it. A positively charged nucleus exists in the center of the atom where electrons rotate around it. A positively charged nucleus exists in the center of the atom where electrons rotate around it.

Centrifugal force = attractive force between nucleus and electron. Centrifugal force = attractive force between nucleus and electron. Centrifugal force = attractive force between nucleus and electron. Centrifugal force = attractive force between nucleus and electron.

Number of (-ve) electrons = number of (+ve) protons inside the nucleus.

Electrons rotate around Electrons rotate around the nucleus in fast movement without emitting or absorbing energy in ground state. the nucleus in fast movement without emitting or absorbing energy in ground state. Electrons rotate around Electrons rotate around the nucleus in fast movement without emitting or absorbing energy in ground state. the nucleus in fast movement without emitting or absorbing energy in ground state.

Bohr reconciled between Rutherford and Maxwell.

Because he assumed that electrons don΄t radiate energy while rotating, so don't fall on nucleus.

Electrons are found only Electrons are found only in definite energy levels and cannot be found at intermediate distances. in definite energy levels and cannot be found at intermediate distances. Electrons are found only Electrons are found only in definite energy levels and cannot be found at intermediate distances. in definite energy levels and cannot be found at intermediate distances.

Each electron has definite energy depending on distance from nucleus: The energy of level increases as its radius increase Each electron has definite energy depending on distance from nucleus: The energy of level increases as its radius increase Each electron has definite energy depending on distance from nucleus: The energy of level increases as its radius increase Each electron has definite energy depending on distance from nucleus: The energy of level increases as its radius increase

“It is a whole number used to show the energy level in which electron exists.”

“Orbits ” in which electrons revolve around the nucleus, their maximum number is 7. “Orbits ” in which electrons revolve around the nucleus, their maximum number is 7. “Orbits ” in which electrons revolve around the nucleus, their maximum number is 7. “Orbits ” in which electrons revolve around the nucleus, their maximum number is 7. n =7 n=6n=5n=4n=3n=2n=1 n=6n=5n=4n=3n=2n=1 Atom absorbs energy energy Atom absorbs energy energy Atom emits energy energy Atom emits energy energy

Nucleus Electron Orbit Energy Levels

“Amount of energy absorbed or emitted when an electron jumps from one level to another”.

Electron moves only : Electron moves only : If the energy absorbed or emitted = 1 Quantum. If the energy absorbed or emitted = 1 Quantum. (There is no fraction of quantum. ) (There is no fraction of quantum. ) Electron moves only : Electron moves only : If the energy absorbed or emitted = 1 Quantum. If the energy absorbed or emitted = 1 Quantum. (There is no fraction of quantum. ) (There is no fraction of quantum. )

Losing the quantum in form of light of definite wavelength produces a characteristic spectral line Losing the quantum in form of light of definite wavelength produces a characteristic spectral line Losing the quantum in form of light of definite wavelength produces a characteristic spectral line Losing the quantum in form of light of definite wavelength produces a characteristic spectral line

Difference in energy between energy levels “Energy gap” is not equal. Difference in energy between energy levels “Energy gap” is not equal. Difference in energy between energy levels “Energy gap” is not equal. Difference in energy between energy levels “Energy gap” is not equal.

2L2L 1K1K 1K1K 3M3M4N4N 5O5O 6P6P 7Q7Q Energy gap decreases far from nucleus. Energy gap decreases far from nucleus. Energy gap decreases far from nucleus. Energy gap decreases far from nucleus.

Because the electron loses Because the electron loses a quantum of energy in the form of light of definite wavelength producing a characteristic spectral line. Because the electron loses Because the electron loses a quantum of energy in the form of light of definite wavelength producing a characteristic spectral line.

The multitude of atoms absorb different amount of energy to excite their electrons to higher energy levels,

then they radiate this energy in form of light producing different spectral lines.

N.B.: These lines correspond to the energy levels from which their electrons are transmitted back to the ground. N.B.: These lines correspond to the energy levels from which their electrons are transmitted back to the ground. N.B.: These lines correspond to the energy levels from which their electrons are transmitted back to the ground. N.B.: These lines correspond to the energy levels from which their electrons are transmitted back to the ground.

Atom gains energy Atom loses energy Atom in ground state Atom in excited state é jumps from a lower level to a higher one. é jumps from a lower level to a higher one. é jumps from a higher level to a lower one

He explained the hydrogen spectrum He introduced the idea of quantized energy for electrons in the atom He introduced the idea of quantized energy for electrons in the atom

He assumed that electrons do not radiate energy when moving in the ground state.

Did not succeed to explain the spectrum of other elements except that of hydrogen.

He considered the electron is a particle onlyand did not consider that it also has wave properties. is a particle only and did not consider that it also has wave properties. He considered the electron is a particle onlyand did not consider that it also has wave properties. is a particle only and did not consider that it also has wave properties.

He postulated that it is possible to determine precisely both location and speed of an electron at the same time which is experimentally impossible.

He described that the electron is a particle moving in a circular planer orbit,