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Physics > Atomic structure > Flashcards

Atomic structure Flashcards

1
Q

What are all things made of?

A

Atoms.

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2
Q

What does an atom consist of?

A

A small nucleus containing protons and neutrons, with electrons orbiting it.

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3
Q

Where is most of the mass concentrated in an atom?

A

The nucleus.

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4
Q

What is the diameter of an atom in standard form (m)?

A

1 x 10^-10m

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5
Q

What is the diameter of a nucleus in standard form (m)?

A

1 x 10^-14m

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6
Q

How are electrons arranged in an atom?

A
  • At different distances from the nucleus (call them energy levels for physics, shells for chemistry).
  • The further away from the nucleus, the higher the energy level is.
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7
Q

What is electromagnetic radiation?

A

A group of waves which carry energy e.g. light.

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8
Q

What happens if an electron absorbs an electromagnetic wave?

A

It will move further from the nucleus to a higher energy level.

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9
Q

What can electrons with extra energy do?

A

Release an electromagnetic wave and fall back to a lower energy level.

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10
Q

What do all atoms of a particular element share?

A

The same number of protons.

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11
Q

What is the atomic number?

A

Number of protons in a nucleus.

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12
Q

What is the mass number?

A

The total number of protons and neutrons in a nucleus.

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13
Q

What are isotopes?

A

Atoms that have the same number of protons but a different number of neutrons.

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14
Q

Why are most atoms neutral?

A
  • Most of them have the same number of protons and electrons.
  • As protons have a charge of +1 and electrons have a charge of -1, these balance out to make the atom neutral/uncharged.
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15
Q

What happens when an atom has a full outer shell?

A

It becomes stable.

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16
Q

What happens when metals react with other elements?

A
  • They have a few electrons in their outer shell that they lose to become stable.
  • The net charge of the atom becomes positive.
  • It becomes a cation (positive ion).
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17
Q

What happens when non-metals react with other elements?

A
  • They have almost full outer shells, so they gain electrons to become stable.
  • The net charge of the atom becomes negative.
  • It becomes an anion (negative ion).
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18
Q

What is an ion?

A
  • A charged atom.
  • Negative = anion.
  • Positive = cation.
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19
Q

What is charge?

A
  • A physical property of matter.
  • Particles can be positively or negatively charged.
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20
Q

What is an electrostatic force?

A

A force that repels like charges and attracts opposite charges together.

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21
Q

What did Thomson discover?

A
  • Tiny, negatively charged particles called electrons.
  • He thought that electrons were surrounded by a ball of positive charge.
  • This is called the plum pudding model.
22
Q

What experiment did Geiger and Marsden carry out?

A
  • They bombarded atoms in a thin sheet of gold foil with tiny positive charges called alpha particles.
  • They expected the alpha particles to go through.
  • Instead, some were deflected at large angles and some even bounced back.
23
Q

What did Rutherford conclude from Geiger and Marsden’s experiment?

A

There is a small, positive nucleus in an atom’s centre containing most of the mass, the rest of the atom is mostly empty space.

24
Q

What did Bohr discover?

A

He did calculations to find out that electrons orbit the nucleus at specific distances.

25
Q

What did various scientists discover after Bohr’s calculations?

A

Later experiments showed the nucleus could be divided into smaller positively charged particles called protons.

26
Q

What did Chadwick discover?

A

Uncharged particles called neutrons.

27
Q

What conclusions were drawn from Geiger, Marsden and Rutherford’s experiment?

A
  • Most alpha particles went straight through the gold foil = the atom is mostly empty space.
  • Some were deflected at large angles = the nucleus of the atom is positive.
  • Some bounced backwards = there is a very small nucleus containing most of the mass.
28
Q

What is are isotopes?

A

Atoms with the same number of protons but a different number of neutrons.

29
Q

What are unstable isotopes called?

A

Radioactive.

30
Q

What is radioactive decay?

A

A random process when the nucleus of an unstable isotope gives out radiation as it changes to become more stable.

31
Q

What is activity (in radioactive terms)?

A

The rate in which a radioactive source decays (no. of decays per second). It is measured in becquerel (Bq).

32
Q

How do we measure radioactivity?

A
  • We use a device called a Geiger-Muller tube.
  • Count rate is the no. of decays recorded each second by the detector.
  • It does not equal activity as the detector can’t record every single decay as it cannot surround the source on all sides.
33
Q

How many types of radiation are there?

A

Four; alpha particle, beta particle, gamma wave and neutron.

34
Q

What is an alpha particle made of?

A

2 protons and 2 neutrons (a helium nucleus).

35
Q

What is a beta particle made of?

A

A neutron that turns into a proton and releases a fast moving electron.

36
Q

What is a gamma wave made of?

A

An electromagnetic wave.

37
Q

What is the range in air for each type of radiation (excluding the neutron)?

A
  • Alpha particle: < 5cm
  • Beta particle: ~ 1m
  • Gamma wave: > 1km
38
Q

What is the ionising ability for each type of radiation (excluding the neutron)?

A
  • Alpha particle: high
  • Beta particle: medium
  • Gamma wave: low
39
Q

What is each type of radiation stopped by (excluding the neutron)?

A
  • Alpha particle: paper
  • Beta particle: thin aluminium
  • Gamma wave: thick lead
40
Q

What is ionising ability?

A

How likely the radiation is to remove electrons from the atoms they collide with.

41
Q

What can the emission of nuclear radiation change?

A

The mass or atomic number of an atom.

42
Q

How are alpha particles written as in an equation?

A

He (mass number = 4, atomic number = 2) like helium.

43
Q

How are beta particles written as in an equation?

A

e (mass number = 0, atomic number =-1) like an electron.

44
Q

How is alpha decay written as an equation?

A

atom -> new atom (mass decreased by 4, atomic by 2) + He

45
Q

How is beta decay written as an equation?

A

atom -> new atom (atomic increased by 1) + e

46
Q

Why does gamma decay not require an equation?

A

It does not change the mass of atomic number of an atom.

47
Q

What is the half-life of a radioactive isotope?

A

The time it takes for the number of nuclei in a sample of the isotope to halve.

48
Q

What is irradiation?

A

When radiation from a source hits an object. This does not make the object radioactive.

49
Q

What does radiation do to matter?

A
  • It ionises it.
  • This can damage tissues leading to systems in the body stopping working (radiation sickness).
  • It also may cause cells to replicate quickly or mutate; this is cancer.
50
Q

What is contamination?

A
  • When radioactive substances are mixed with other substances.
  • This is very dangerous as the contaminating atoms will continue to decay.
51
Q

What are the safety precautions for handling radioactive isotopes?

A
  • Minimising exposure time.
  • Using lead screens.
  • Storing sources in lead containers.
  • Wearing disposable clothes.
  • Increasing the distance from the source using tongs or robotic arms.
52
Q

What are the medical uses for radioactive isotopes?

A

They are used in hospitals for x-rays but the dose for patients should be kept to a minimum.

Physics (4 decks)

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