Lesson 7: Development of atomic model

Question 1

What causes a scientifical model to be changed or replaced ?

Answer 1

• New experimental evidence that can’t explain the previous model.

Question 2

What were atoms thought to be before the discovery of the electron?

Answer 2

• Atoms are tiny spheres
• They are indivisble

Question 3

What was the plum pudding model?

Answer 3

• Atoms are a ball of postitive charge with electrons embeded.

Question 4

Who discovered the nuclear model?
What was the nuclear model?

Answer 4

• Ernst Rutherford discovered model
• Mass concentrated in nucleus// nucleus = charged.
• Electrons in fixed poisitions on edge of atom.
• Proved using “Alpha scattering experiment. “

Question 5

What was the alpha scattering experiment ?

Answer 5

1.) Alpha particles (nucleus of helium atom) were fired at gold atoms.
2.) Most went through the gold atom, however, some deflected (suggesting there was something in the atom to do so.)
3.) The proton in nucleus deflected the poistive alpha.
4.) This proved the presence of the nucleus.

Question 6

What was Bohr’s Model?

Answer 6

• Positive charge concentrated in nucleus.
• Electrons orbit the nucleus at specific distances.

Question 7

Who discovered the neutron?
When?

Answer 7

• James Chadwick discovered the neutron
• 20 years after nucleus became acceptable scientifical idea.

Question 8

What is the order of subatomic particle’s discovery?

Answer 8

• Electrons
• Protons
• Neutrons

Question 9

What 3 things were concluded from Rutherford’s nuclear model?

Answer 9

ATOM IS:
- Mostly empty space
- Mass concentrated in nucleus
- Positive charge in nucleus

Question 10

What did the alpha particles going straight through foil show?

Answer 10

• That the atom is mostly empty space.

Question 11

What did the alpha particles deflecting through large angles show?

Answer 11

• Positive charge concentrated in centre.
• Mass concentrated in centre.

Question 12

What did the alpha particles having slight deflection show?

Answer 12

• Nucleus must have a positive charge (for repulsion to occur.)

Question 13

What led to the proton being discovered?

Answer 13

• Found out that positive charge of nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton
  was given to these particles.