Atoms Flashcards
(19 cards)
What is the source material used in Rutherford’s experiment?
S’ is the source of alpha particles
How were the alpha particles formed into a beam?
The alpha particles were collimated into a fine beam using lead bricks.
What was the target material and its thickness in the experiment?
The target was a gold foil having thickness 2.1 × 10⁻⁷ m.
How were the scattered alpha particles detected?
The scattered alpha particles were observed using a rotatable detector consisting of ZnS screen and microscope.
What was Rutherford’s first key observation about the alpha particles
Most of the alpha particles went straight through the foil without suffering any deviation.
What percentage of alpha particles showed significant scattering?
Only about 0.14% of incident alpha particles scattered by more than 1°.
What was observed about backward scattering?
About one alpha particle in 8,000 deflects by more than 90°, showing backward scattering.
What components made up the detection system?
The detection system consisted of a ZnS screen and microscope.
The graph between the total no of scattered alpha particles N(0) and scattering angle (0-)
Conclusion of rutherfords experiment
•Since modt of the alpha particles go straight through the foil without any deviation. Therefore most of the space inside the atom is empty.
• to deflect the alpha particles backward greater mass and positive charge of the atom where concentrated at the the centre. Later named thos region as nucleus
• the repulsive force between positively charged alpha particles ( +2e) and gold nucleus of charge ( +Ze) is given by coulomb’s law ( notes)..
Rutherfords nuclear atomic model
•The entire positive charge and most of thr mass od the atom concentrated at the centre as nucleus.
•electrons revolve around the nucleus just as planets revolve around the sun in all possible radii
• atom has a whole electrically neutral
• therefore total charge on the nucleus is equal to the total charge of the electrons
The trajectory of the alpha particles can be computed employing ________
Newton’s 2nd law of motion and coulomb’s law
The trajectory of alpha particles can be computed employing the________
Newton’s second law of motion and coulomb’s law
The _____ and the ____ of the force of an alpha particle continuously changes as it approaches the nucleus and recedes away from it
Magnitude and direction
What is impact parameter?
The perpendicular distance of the initial velocity vector of the alpha particle from the centre of the nucleus
What is the significance of impact parameter ?
When b is small,.the scattering angle is large because electrostatic force os large.
What is the distance of the closest approach ?
It is the distance from the nucleus where whole kinetic energy of the particle converts into potential energy and the alpha particle cannot go further close to the nucleus is called distance of the closest approach.
What Is the significance of the distance of closest approach?
To find the size of the nucleus
Drawbacks of rutherfords model
• it failed to explain the stability of the atom.
• it failed to explain the line spectrum of the atoms of different elements
