Discovery and Research on the Electron

Question 1

• Who discovered the e/m ratio of the electron?
• What year was the e/m ratio discovered?

[2 marks]

Answer 1

1. JJ Thompson
2. 1897

Question 2

What is the e/m ratio of an electron? [1 mark]

Answer 2

1.7 x 10^-11 C kg^-1

Question 3

Recite formula required to calculate the mass of an electron using e/m (charge to mass ratio) and e (charge) [1mark]

Answer 3

e /e:m = charge/ charge to mass ratio

Question 4

• Who was behind the oil drop experiment?
• What year was the charge of a single electron discovered?

[2 marks]

Answer 4

1. R. Millikan
2. 1909

Question 5

What’s the charge of 1 e^- ? [1 mark]

Answer 5

1.6 x 10^-19 C

Question 6

What was the:

• Independent variable (Thing being investigated)
• Dependant variable (Thing being changed)

In the oil drop experiment? [2 marks]

Answer 6

Independent Variable: Charge of electron

Dependent variables: Strength of electric field & Mass of oil drop

Question 7

What’s the molar mass of H? [1 mark]

Answer 7

1 x 10^-3 kg

Question 8

What is the value for m_H/m_e-?

Answer 8

1,852

Question 9

How can we tell that the electron is small compared to the atom?

[1 mark]

Answer 9

m_H/ m_e-= 1,852

Question 10

What’s the mass (kg) of 1 electron? [1 mark]

Answer 10

9 x 10^-31 kg

Question 11

What’s the molar mass of e^- [1 mark]

Answer 11

5.4 x 10-7 kg