Discovery of Nucleus Flashcards
What was the John Dalton Model of the atom?
A SOLID SPHERE.
What was JJ Thompson’s model?
NEGATIVE ELECTRONS embedded in the SOLID SPHERE of POSITIVE MATTER
What experiment disagreed with JJT model?
Alpha scattering experiment carried out by Rutherford.
What was it?
Alpha particles fired at THIN GOLD FOIL in VACUUM CHMABER.
What was expected?
MOST particles to PASS ( as charges are balanced so spread out so no deflection) through with little amount of deflection of little angles
What did he see?
Most did pass through
Small number of large deflection (as the REFLECTED ANGLE INCREASED the number of DELECTION DECREASED)
VERY FEW were GREATER THAN 90 degrees
New nuclear model after this:
1) Most of atom is empty space
» Nucleus is much smaller than the rest of atom with the MASS and POSTIVE CHARGE CONCENTRATED in the CENTRE
2) Electrons orbit in the space outside the nucleus
Why did this happen?
1) Most of atom in empty space- so most pass through
2) The particles that went NEAR the NUCLEUS got REPELLED so DEFLECTED.
3) Some went really close and straight in front of it so 90 degrees
How can electrons move in orbit shells?
It can move AWAY or CLOSER to the nucleus but it can be in SMALL STEPS or JUMP.
The movement must be EQUAL TO THE ENERGY DIFFERENCE EBTWEEN SHELLS.
Why did NEIL BOHR out the theory of electrons orbit in shells at SPECIFIC ENERGY VALUE and DISTANCE?
To explain why the electrons don’t collapse.
How do electrons move away?
By ABSORBING EM RADIATION.
Has to be the exact value to go to next level or it doesn’t move.
How do electrons move closer to nucleus?
By EMITTING EM RADIATION.
What is the atomic number?
The number of protons (Z)
What is mass number?
number of protons + neutrons (A)
What are isotopes?
Atoms of the same element with different number of neutron but same number of protons and electrons.
