[Part 3]- P7- Atomic structure ⚛️

Question 1

How do you work out the number of neutrons?

Answer 1

Mass number ➖ atomic number

Question 2

How do you work out the number of protons?

Answer 2

• look at the atomic number (the smallest number)

Question 3

What does the term ‘atomic number’ vs ‘mass number mean?’ [2]

Answer 3

Atomic number is the number of protons in an atom ; mass number is the total number of neutrons and protons in an atom.

Question 4

How do you work out the number of electrons?

Answer 4

The number of electrons in an atom= number of protons in an atom [atomic number]

Question 5

Why did new evidence from Rutherford’s scattering experiment, lead to a change in the atomic model? [1]

Hint: plum pudding disapproved.

Answer 5

• The experimental results of the gold foil experiment could not be explained using the plum pudding model.
• so the plum pudding model was disapproved and a, new model called the nuclear model (Bohr) was made to match the results.

Question 6

What’s the difference between the nuclear model of an atom + the plum pudding model? [5]

Hint: empty space, distance, distributed throughout, ball of.., mass…

Answer 6

Nuclear model of atom:

• The atom is mostly empty space + negative electrons orbit the nucleus at a distance
• almost all the mass of an atom was actually concentrated in the positively charged nuclues.

Plum pudding model:

• the atom is a positively charged ‘ball’ of positive charge
• mass of atom is evenly distributed.
• negative electrons are distributed through the atom.

Question 7

What are the observations in Rutherford’s experiment that lead to conclusions? [1]

Hint: deflected

Answer 7

• Some of the alpha particles were deflected= so the centre must have a positive charge + that repelled alpha particles.

Question 8

What are the observations in Rutherford’s experiment that lead to conclusions? [1]

Hint: through 🏆foil, model wrong

Answer 8

• most of the alpha particles went straight through the gold foil = so therefore atoms are mainly empty space. [meaning the plum pudding model had to be wrong]

Question 9

What are the observations in Rutherford’s experiment that lead to conclusions? [1]

Hint: straight back 🔙 ,mass

Answer 9

• Some alpha particles bounced straight back= so the mass of an atom, must be concentrated in the centre/the nucleus
• [nuclear model replaced plum pudding model]

Question 10

During alpha decay, can you tell me what happens to the mass number and atomic number?

Answer 10

• during alpha decay, the atomic number decreases by 2; the mass number decreases by 4.

Question 11

What is the rule for beta decay?

Answer 11

• In beta decay, the atomic number increases by 1; the mass number dosen’t change.

Question 12

What is the equation for net decline?

Hint: n half…

Answer 12

Net decline= initial no. ➖️ no. after n half lifes
________________
Initial number

Question 13

State the four types of emitting radiation [4]

Answer 13

• alpha
• beta
• gamma
• [neutron]

Question 14

What did the ancient greeks/Democritus think about atoms?

Answer 14

• everything is made of atoms + atoms are tiny spheres which can’t be divided.

Question 15

What are the steps for the alpha scattering expirement? [2]

Answer 15

• took a piece of gold foil [gold can be hammered into a few atoms thick]
• they then fired alpha particles from a helium nuclei.

Question 16

How were protons and neutrons discovered? [2]

Hint: positive charge–> positive particles

Answer 16

• Scientists found the positive charge of a nucleus, is due to positive particles [called protons]
• and (James) Chadwick discovered that the nucleus also contains neutrons, which have a neutral charge