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Physics > P7-Atomic Structure > Flashcards

P7-Atomic Structure Flashcards

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1
Q

What are alpha particles and whats their numbers

A

4
He
2

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2
Q

What are the numbers for beta

A

0
B
-1

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3
Q

What are the numbers for gamma and what are gamma waves

A

0
Electro magnetic waves
0

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4
Q

What can stop alpha particles

A

Piece of paper

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5
Q

What can stop beta particles

A

Few sheets of alluminium

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6
Q

What can stop gamma waves

A

Several cm of led

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7
Q

How far so alpha particles travel

A

5cm

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8
Q

How far do beta particles travel

A

1m

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9
Q

How far do gamma particles travel

A

Unlimited distance

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10
Q

What happens to the activity of a source as more unstable atoms decay

A

Reactivity decreases

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11
Q

What is count-rate and what is used to measure it

A

The number of decays record each second by a geiger counter

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12
Q

What does it mean if theres a shorter half life in a radioactive dice graph

A

It is more reactive as less radioactive nuclei have decayed

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13
Q

How do you calculste the count rate after 3 half lives with a count rate of 60

A

60/2^3=7.5
Count rate before/2^half lives

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14
Q

What did john dalton discover and when did he discover it

A

That matter was made up of tiny spheres (atoms) that couldnt be broken upbyt thought each element was made up of different types of atms. 1804.

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15
Q

What did J J thompson discover and when did he discover it

A
  1. Plum pudding. JJ thompson discovere particles called electrons and that they could be removed from atoms, this proved dalton theory wrong. Atoms where spheres of positive charge with negative electrons stuck in them like a plum pudding.
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16
Q

What did rutherfood discover and when did he discover it. Who did he prove wrong.

A

In 1909. Scientists in rutherfoods lab fired a beam of alpha particles at thing gold foil (alpha scattering) experiments. From the plum pudding model, they expected the particles to pass straight through the gold sheet or only be slightly deflected. Although most did however some were deflected. Plum-pudding model couldnt explain this so J J Thompsons theory was peoven wrong.

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17
Q

How was the nucleus discovered

A

After scientists in rutherfoods lab fired alpha particles at thin gold foil and found some bounced back. This meant most of the mass of the atom must be concentrated at the centre in a nucleus. The nucleus also must have a positive charge as it would repell the positive charged alpha particles. Also because most of the alpha particles passed straight through the atom it meant most of the atom is just empty space.

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18
Q

What did Bohr discover

A

Bohr spdiscovered that electrons orbiting the nucleus do so at certain distances called energy levels.

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19
Q

What did chadwick discover and when did he discover it?

A

In 1932 chadwick proved the existance of the neutron explaining the imbalance between the atomic and mass numbers

20
Q

What is the atomic number

A

The number of protons in an atom

21
Q

What is the mass number

A

The mass of the nucleus, protons + neutrons

22
Q

What is an isotope

A

Atoms with the same number of protons (atomic number) but a different number of neutrons (mass number)

23
Q

What is radioactive decay

A

When unstable isotopes decay into other elements giving out radiation trying to become more stable ( tryinng to balance number of protons and neutrons by getting rid of excess energy)

24
Q

What are the three types of ionising radiation radioactive particles spit out

A

Alpha
Beta
Gamma

25
Q

What is ionising radiation

A

Radiation that knocks electrons off atoms creating positive ions

26
Q

What are alpha particles

A

Helium nuclei

27
Q

Give 3 characteristics of alpha particles

A

Dont penetrate far into materials and stopped quickly and are absorbed by paper
Can only travel a few cm
Strongly ionising

28
Q

What are beta particles

A

Fast moving electron released by the nucleus

29
Q

What happens when a beta particle is emitted

A

A neutron in the nucleus turns into a proton

30
Q

What are gamma rays

A

Waves of electromagnetic radiation released by the nucleus

31
Q

Explain the leval of ionising gamma rays are

A

Weekly ionising because they usually pass through rather than collide with atoms

32
Q

How are nuclear equations written

A

Atom before decay->atom after decay + radiation emitted

33
Q

What is a key rule about nuclear equations

A

The total mass and atomic numbers must be equal on both sides of the equation

34
Q

What happens to an atoms atomic number when it emits an alpha particle

A

The atomic number of the atom reduces by 2 and the mass number reduces by 4

35
Q

How does alpha decay affect the charge and mass of the nucleus. Explain

A

The two positively charged protons that alpha particles contain are removed from the atom decreasing the charge of the atom

36
Q

How does beta decay Affect the charge of the nucleus of an atom. Explain

A

Beta decay increases the charge of the nucleus because a neutron in the nucleus turns into a proton

37
Q

How does gamma rays effect the charge of the nucleus

A

Doesnt change the charge because gamma rays only gets rid of excess energy

38
Q

What is radiation measure by

A

Geiger-muller counter

39
Q

What is half-life

A

The time taken for the number of radioactive nuclei in an isotope to halve

40
Q

What can half-life be used to find

A

The rate at which a source decays, its activity

41
Q

How can ionising radiation be bad

A

Ionising radiation can enter living cells and ionise atoms with them. This can cause danage to the cells or kill them off completely (can cause cancer)

42
Q

What are two common wyas of reducing effects of radiation

A

Keep sources upin lead-lined boxes
Standing behind barriers when using sources

43
Q

What is irradiation

A

Exposure to radiation

44
Q

What is contamination

A

Radioactive particles getting onto objets

45
Q

Why are contaminated particles harmful

A

If contaminated particles get onto or into an object they may decau and release radiation which could cause harm

46
Q

Why are beta and gamma particles more dangerous than alpha particles

A

Because beta and gamma particles can penetrate into the body however alpha particles cant

47
Q

Why are beta particles less damaging inside the body compared to alpha particle

A

Beta particles are less damaging because rsdiation is absorbed over a wider area and some passes out of the body too as they have the lowst ionising power. Alpha sources however do all their damage in a very localised area.

Physics (5 decks)

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