Radioactivity

Question 1

Describe Bohr’s atomic model

Answer 1

In this model, the nucleus is orbited by electrons, which are in different energy levels.

Question 2

Describe Democritus’ atomic model

Answer 2

Was a giant ball as he claimed they were indivisible

Question 3

Describe Dalton’s atomic model

Answer 3

Was the same as Democritus’s model

Question 4

Describe Thomson’s atomic model

Answer 4

He proposed that electrons were embedded into a positively charged-soup hence the name plum-pudding model.

Question 5

Describe Rutherford’s atomic model

Answer 5

The atom had a tiny positively charged core named the nucleus while the electrons circulated the nucleus like planets in the solar system.

Question 6

Describe Schrodinger’s atomic model

Answer 6

He treated electrons as matter waves with the nucleus being in the centre of the waves.

Question 7

Who proposed the name for atom?

Answer 7

Democritus named it atomos

Question 8

What does atomos mean?

Answer 8

Not to be cut

Question 9

Why was Democritus theory rejected?

Answer 9

Aristotle and Plato favoured the earth, fire, air and water approach to the nature of matter. Their ideas held sway because of their eminence as philosophers.

Question 10

Who caused the acceptance of the existence of atoms?

Answer 10

John Dalton

Question 11

What was Dalton’s theory?

Answer 11

He deduced that all elements are composed of atoms. Atoms are indivisible and indestructible particles.
Atoms of the same element are exactly alike.
Atoms of different elements are different.
Compounds are formed by the joining of atoms of two or more elements.

Question 12

Who provided the idea of something being smaller than atoms?

Answer 12

J.J. Thomson

Question 13

What was Thomson’s theory?

Answer 13

Atoms were made from a positively charged substance with negatively charged electrons scattered about, like raisins in a pudding.

Question 14

What was Rutherford’s theory?

Answer 14

Rutherford concluded that an atom had a small, dense, positively charged center that repelled his positively charged “bullets.”
He called the centre of the atom the “nucleus”
The nucleus is tiny compared to the atom as a whole.

Question 15

Name of Thomson’s model

Answer 15

Plum pudding model

Question 16

What was Bohr’s theory?

Answer 16

According to Bohr’s atomic model, electrons move in definite orbits around the nucleus, much like planets circle the sun. These orbits, or energy levels, are located at certain distances from the nucleus.

Question 17

Who invented the wave model?

Answer 17

Ernest Schrodinger

Question 18

What was Schrodinger’s theory?

Answer 18

Electrons do not move about an atom in a definite path, like the planets around the sun.
In fact, it is impossible to determine the exact location of an electron. The probable location of an electron is based on how much energy the electron has.
According to the modern atomic model, an atom has a small positively charged nucleus surrounded by a large region in which there are enough electrons to make an atom neutral.

Question 19

Why do we change models?

Answer 19

We (scientists) change to using a new model, mainly because the old model has been shown not to work well enough.
This is usually because of new evidence that doesn’t fit the old model.
And this is usually because new technology has been invented that can do better (more accurate, more detailed or just different) experiments. This ‘new technology’ can even include new mathematics.

Question 20

Define nuclear radiation

Answer 20

When the atom’s nucleus falls apart or decays resulting in the large production of energy often along with particles emitted from the nucleus. The radiating or spreading out of the particles from the nucleus is known as nuclear radiation.

Question 21

Are atoms stable?

Answer 21

Not all are stable?

Question 22

3 types of radiation

Answer 22

Alpha and Beta particles radiation and Gamma rays radiation

Question 23

What are alpha particles?

Answer 23

2 protons and neutrons (helium particle)

Question 24

Mass of alpha particles

Answer 24

4 AMU

Question 25

Alpha particles penetration

Answer 25

Penetration: Not much (blocked by paper or 5-10cm air)

Question 26

Alpha particles charge

Answer 26

+2

Question 27

What is beta radiation?

Answer 27

An electron

Question 28

Charge of beta radiation?

Answer 28

-1

Question 29

Beta particles penetration

Answer 29

Penetration: (Blocked by sheet of wood, metal, some plastics)

Question 30

Mass of Beta particles

Answer 30

very little

Question 31

Symbol for 3 types of radiation

Answer 31

Alpha: α
Beta:β
Gamma:γ

Question 32

What is gamma radiation?

Answer 32

An electromagnetic wave with a very short wavelength (high energy, above x-rays)/ photon emission

Question 33

Mass and charge of gamma radiation

Answer 33

None

Question 34

Gamma radiation penetration

Answer 34

Penetration: Very! (blocked by lead sheets, concrete, metres of material)

Question 35

Device to measure and detect radiation

Answer 35

The main tool is a Geiger Muller tube, connected to a counter. This is better known as a Geiger counter.

Question 36

How does a Geiger counter work?

Answer 36

Radiation ionises (knocks electrons off) a gas inside the tube. This movement of electrons creates a current, that an electric circuit detects and counts.

Question 37

Provide 3 examples of how radiation is used

Answer 37

To locate certain cancers
Smoke detectors
Detecting leaks underground

Question 38

Who began the studies of quantum theory?

Answer 38

Ernest Schrodinger

Question 39

How did Democritus discover the atom?

Answer 39

He conducted a simple experiment where he took a seashell and broke it half and continued doing this until he theorised that he would get to the indivisible atom.

Question 40

How did Thomson discover electrons?

Answer 40

He directed the cathode rays between two parallel aluminum plates to the end of a tube. When the top aluminum plate was negative, the rays moved down; when the upper plate was positive, the rays moved up.

Question 41

How did Rutherford discover the nucleus?

Answer 41

Rutherford’s experiment involved firing a stream of tiny positively charged particles at a thin sheet of gold foil (2000 atoms thick)
Most of the positively charged “bullets” passed right through the gold atoms in the sheet of gold foil without changing course at all.
Some of the positively charged “bullets,” however, bounced away from the gold sheet as if they had hit something solid.
This could only mean that the gold atoms in the sheet were mostly open space. Atoms were not a pudding filled with a positively charged material.
Rutherford concluded that an atom had a small, dense, positively charged centre that repelled his positively charged “bullets

Question 42

How did Dalton discover compounds?

Answer 42

He carefully examined the experiments of others (and repeated a few) and realised that elements seemed to join in very fixed ratios, as if 1 ‘part’ of an element always connected to 2 (or 3 or 4) parts of another element.