SC3 - Atomic Structure ✓

Question 1

SC3a - Describe JJ Thomson’s Experiment

Answer 1

● Used a cathode-ray tube to conduct an experiment

● This discovery identified an error in Dalton’s atomic theory. Atoms can be

divided into smaller parts.

● Because the beam moved away from the negatively charged plate and toward

the positively charged plate, Thomson knew that the particles must have a negative charge.

● Thomson proposed a model of an atom called the “plum-pudding” model, in

which negative electrons are scattered throughout soft blobs of positively

charged mat

Question 2

SC3a - Describe the structure of an atom

Answer 2

• Protons and neutrons centred in a nucleus.
• Electrons orbiting outside in electron shells.

Question 3

SC3a - Descrie John Dalton’s 4 points of atomic theory

Answer 3

• All matter is made up of atoms
• Atoms are small, hard, spheres cannot be broken down into smaller parts
• Atoms cannot be created or destroyed
• The atoms in an element are all identical

Question 4

SC3a - Names the three subatomic particles as well as their relative mass and charge.

Answer 4

• Protons:
  
  • M: 1
  • C ⁺¹
• Neutron:
  
  • M: 1
  • C Neutral (0)
• Electron:
  
  • M: 1/1835 (negligible)
  • C ^-1

Question 5

SC3a - Who discovered the neutron in 1932?

Answer 5

James Chadwick

Question 6

SC3b - Explain why Rutherford’s gold foil experiment suggests that atoms are mostly empty space.

Answer 6

• Most of the alpha particles passed straight through the gold foil.

Question 7

SC3b - Describe Rutherford’s gold foil experiment

Answer 7

• Ernest Rutherford shot alpha particles at a sheet of gold foil and predicted that the particles would go through the sheet, but some of them refracted off.

Question 8

SC3b - What is a mass number?

Answer 8

• The number of protons + neutrons in an atom (the mass).
• The top number on the symbol for an element.

Question 9

SC3b - What is an atomic number?

Answer 9

The number of protons in an atom. the bottom number on the symbol for an element

Question 10

SC3b - Explain how Rutherford’s gold foil experiment proved the existence of a nucleus.

Answer 10

• Some of the alpha particles were being deflected and very few were bouncing right back. These proved the existence of a small, positively charged, central nucleus.

Question 11

SC3c - How do you calculate the Ar of an element from the abundance of its isotopes.

Answer 11

(M₁ x A₁) + (M₂ x A₂) ^_(etc.) ÷ 100 (M=Mass A=Abundance)

Question 12

SC3c - What does the symbol A_r stand for and what does it mean?

Answer 12

• Relative Atomic Mass.
• The average mass of the naturally occurring form(s) of an element in relation to a Carbon-12 atom

Question 13

SC3c - What is an isotope?

Answer 13

Two atoms (of the same element) with the same atomic number but different mass numbers (amounts of neutrons)

Question 14

SC3c - Why does chlorine have a mass number with a decimal?

Answer 14

• It is its relative mass.
• There are two isotopes of chlorine, 35 and 37.
• Chlorine - 35 is more abundant than 37.

Question 15

SC3a - How many times bigger is the diameter of the overall atom compared to the diameter of the nucleus?

Answer 15

Up to 100,000x bigger