C3 Atoms

Question 1

What are the three ideas of John Daltons Theory about the atom?

Answer 1

• Atoms cannot be created, divided or destroyed,
• Atoms of the same element are exactly the same and atoms of different elements are different,
• Atoms join with other atoms to make substances

Question 2

How have Daltons ideas of the atom changed?

Answer 2

-Subatomic particles were discovered.
-Therefore they are not the smallest things and so can be further divided

Question 3

What did JJ Thomson conduct an experiment using?

Answer 3

Used a cathode-ray tube (negatively charged)

Question 4

How did JJ Thomson’s experiment prove that atoms have a charge?

Answer 4

Particles from the beam moved away from the negatively charged cathode to the positively charged plate, so he knew the particles had a negative charge.

Question 5

How did this disprove Dalton’s earlier proposals?

Answer 5

It proved that atoms can be divided into smaller parts because there are subatomic particles with charges.

Question 6

Describe Thomson’s plum pudding model.

Answer 6

negative electrons are scattered throughout soft blobs of positively
charged material.

Question 7

What are subatomic particles?

Answer 7

Particles inside an atom
e.g protons, neutrons and electrons

Question 8

What is the mass of an electron?

Answer 8

1/1836
OR
Negligible

Question 9

Explain why atoms contain equal number of protons and electrons.

Answer 9

Atoms are neutral and the charges on a proton are +1 and on an electron are -1
therefore amount of protons = amount of electrons, so that the charges cancel

Question 10

Definition of an isotope.

Answer 10

Atoms of the same element with a different atomic mass due to different numbers of neutrons

Question 11

How do you calculate the relative atomic mass of an element from
the relative masses and abundances of its isotopes?

Answer 11

R.A.M. =
(mass of isotope-A x % of isotope-A) + (mass of isotope-B x % of isotope-B)
100
=
(35 x 75) + (37 x 25)
100
=
3550
100
R.A.M. = 35.5

Question 12

Who was the first person to explain atomic structure?

Answer 12

Ernest Rutherford

Question 13

what experiment did Ernest Rutherford conduct?

Answer 13

Gold Foil Experiment

Question 14

Explain the golf foil experiment.

Answer 14

• A positively charged beam was shot at gold foil and some particles passed straight through the gold foil relating to the plum pudding model.
• However some of the particles were deflected to the sides
  a bit, and a few bounced straight back.
• therefore there was a nucleus with positive charge and most of the particles passed through OPEN SPACE