Atomic Structure Flashcards
1
Q
What are atoms?
A
Atoms are the building blocks of all matter
2
Q
What is the radius of an atom?
A
1 × 10^-10 m
3
Q
What is contained in the nucleus of an atom?
A
- Protons
- Neutrons
4
Q
What charge do protons have?
A
Positive charge
5
Q
What charge do neutrons have?
A
No charge
6
Q
What is the relative atomic mass of protons and neutrons?
A
One unit
7
Q
What is the charge of electrons?
A
Negative charge
8
Q
How does the mass of an electron compare to that of protons or neutrons?
A
Almost no mass (1/2000 the mass of a proton or neutron)
9
Q
What is the relationship between the number of protons and electrons in a neutral atom?
A
The number of protons is equal to the number of electrons
10
Q
What is the atomic number?
A
The number of protons in an atom
11
Q
How does the atomic number relate to the periodic table?
A
Elements are ordered by their atomic number
12
Q
What is the mass number?
A
The total number of protons and neutrons in the nucleus
13
Q
How can the number of neutrons be calculated?
A
Number of Neutrons = Mass Number - Atomic Number
14
Q
Define isotopes.
A
Atoms of the same element with an equal number of protons but different numbers of neutrons
15
Q
What happens when an atom loses electrons?
A
It becomes ionized and turns into a positive ion
16
Q
What is nuclear notation?
A
A way to represent the atomic and mass numbers with the atomic symbol
17
Q
What is the significance of the mass number of chlorine being given as 35.5?
A
It reflects the abundance of its isotopes, with one isotope being more common than the other
18
Q
True or False: The number of neutrons affects the chemical properties of an atom.
A
False
19
Q
Fill in the blank: Electrons can be knocked out of the outer energy levels of an atom through _______.
A
Friction, electromagnetic radiation, or chemical reactions
20
Q
What are positive ions?
A
Atoms that have lost one or more electrons and have a positive charge
21
Q
What can cause an atom to become a positive ion?
A
- Friction
- Absorption of electromagnetic radiation
- Chemical reactions
22
Q
What does it mean for an atom to be ionized?
A
It has lost electrons and has a net positive charge
23
Q
What is the significance of the number of electrons in isotopes?
A
The number of electrons remains the same in different isotopes
24
Q
What is the maximum number of electrons that can occupy the first energy level?
A
2 electrons
25
What is the maximum number of electrons that can occupy the second energy level?
8 electrons
26
What happens to electrons when they absorb electromagnetic radiation?
They move to a higher energy level
27
What occurs when an electron moves back down to its original energy level?
It emits a wave of electromagnetic radiation
28
What is the atomic number of Hydrogen?
1
29
What is the atomic number of Sodium?
11
30
What is the atomic number of Uranium?
92
31
How many protons does a carbon-12 atom have?
6 protons
32
How many neutrons does a sodium atom with a mass number of 23 have?
12 neutrons
33
What is the mass number of Tritium?
3
34
How many neutrons does Chlorine-35 have?
18 neutrons
35
How many neutrons does Chlorine-37 have?
20 neutrons
36
What causes objects or atoms to become charged?
The movement of electrons.
37
What are ions?
Atoms that have gained or lost electrons.
38
What happens when a neutral atom gains electrons?
It becomes negatively charged.
39
What must a neutral atom do to gain a positive charge?
Lose electrons.
40
What is the Plum Pudding Model?
A model proposing that atoms consist of negatively charged electrons embedded in a positively charged mass.
41
Who proposed the Plum Pudding Model?
J.J. Thomson.
42
What discovery led to the replacement of the Plum Pudding Model?
The results of Rutherford's alpha scattering experiment.
43
What did the alpha scattering experiment demonstrate?
That most alpha particles passed through gold foil, some were deflected, and a few bounced back.
44
What is the Nuclear Model of the atom?
A model where nearly all mass is concentrated in a positively charged nucleus with negatively charged electrons orbiting it.
45
What are energy levels in Bohr's model?
Distinct distances at which electrons orbit the nucleus.
46
What is the maximum number of electrons in the first energy level according to Bohr's model?
2 electrons.
47
What is the maximum number of electrons in the second and third energy levels according to Bohr's model?
8 electrons each.
48
Why was the Bohr model accepted over the nuclear model?
It explained experimental findings better and accounted for electromagnetic radiation absorption and emission.
49
What is a proton?
A positively charged particle within the nucleus.
50
Who discovered the proton?
Ernest Rutherford.
51
What is the elementary charge?
The charge of a proton.
52
What is a neutron?
A neutral particle in the nucleus with a mass similar to a proton.
53
Who confirmed the existence of the neutron?
James Chadwick.
54
What did the discovery of the neutron contribute to the atomic model?
It led to a model with a dense nucleus made of protons and neutrons.
55
What is the significance of experimental evidence in scientific models?
Models must explain observations and can be revised based on new evidence.
56
Fill in the blank: The _______ model was replaced by the nuclear model due to its inability to explain experimental results.
Plum Pudding
57
True or False: Protons can move from atom to atom.
False.
58
What did the Plum Pudding Model suggest about the overall charge of an atom?
That the atom is neutral overall.
59
What is the result of firing alpha particles at gold foil in Rutherford's experiment?
Most pass through, some are deflected, and a few bounce back.
60
What is the charge of an alpha particle?
+2.
61
What is Background Radiation?
The radiation that exists around us all the time
## Footnote
Background radiation is a natural phenomenon that has existed on Earth and in outer space, with human activity increasing exposure levels.
62
What are the two types of background radiation?
* Natural sources
* Man-made sources
63
What is a natural source of background radiation?
* Radon gas from rocks
* Cosmic rays from space
* Radiation from rocks and foods
64
Name a man-made source of background radiation.
* Fallout from nuclear weapons testing
* Exposure from medical testing
65
How is background radiation measured?
Using a Geiger-counter
## Footnote
The Geiger-counter detects radiation counts per minute at varying distances.
66
What is the background radiation count determined in the example?
15 counts per minute
67
True or False: Background radiation and cosmic microwave background radiation (CMBR) are the same.
False
68
What does a dosemeter measure?
The amount of radiation in particular areas
69
What is the unit of measurement for radiation dose?
Sieverts (Sv)
70
How much radiation do people typically receive in one year?
About 3 mSv (0.003 Sv)
71
What is the UK limit for nuclear industry employees' radiation exposure in one year?
20 mSv
72
What is the half-life of a radioactive isotope?
The time it takes for the activity of a radioactive source to decrease to half of its original value
73
Which isotope has a half-life of 1 millisecond?
Francium-218
74
Which isotope has a half-life of approximately 700 million years?
Uranium-235
75
Fill in the blank: Isotopes with a short half-life emit a lot of radiation in a _______.
short amount of time
76
What is the advantage of using an isotope with a short half-life in small amounts?
It will quickly lose its radioactivity
77
What is radiotherapy?
The treatment of cancer using radiation
78
What type of radiation is typically used for medical tracers?
Gamma emitters
79
Why are gamma rays used in medical tracers?
They are highly penetrating and can create internal images of the body
80
What is the role of Iodine-131 in medicine?
It is an example of a radioactive tracer
81
True or False: Radiation can cause cancer but is also effective at treating it.
True
82
How does external radiotherapy minimize harm to healthy tissue?
By directing beams of gamma rays at the tumor from different angles
83
What is the purpose of gamma radiation in sterilizing medical equipment?
It is the most penetrating type of radiation
84
What are the risks associated with nuclear radiation in medicine?
* Kill or damage living cells
* Cause cancer
* Cause mutations
85
Fill in the blank: A suitable medical tracer must have a half-life that is _______ enough to move around the body.
long
86
What is a misconception about radioactive decay?
The mass of the sample decreases with each decay
87
What should be kept to a minimum in the use of radiation in medicine?
Exposure to radiation
88
What is nuclear fission?
The splitting of a large, unstable nucleus into two smaller nuclei
## Footnote
Nuclear fission releases energy stored within the nucleus of an atom.
89
Which isotopes are commonly used as fuels in nuclear power stations?
Isotopes of uranium and plutonium
## Footnote
Both undergo fission.
90
What happens during nuclear fission when a neutron collides with an unstable nucleus?
The nucleus splits into two smaller nuclei (daughter nuclei) and emits two or three neutrons and gamma rays.
91
What is spontaneous fission?
Fission that occurs without additional energy being put into the nucleus.
92
What is induced fission?
Fission that occurs when an unstable nucleus absorbs a neutron.
93
What is the half-life of uranium-235?
700 million years.
94
What is a chain reaction in nuclear fission?
A process where each fission produces neutrons that can induce further fission reactions.
95
What is required to keep a controlled chain reaction in a nuclear reactor?
The number of free neutrons in the reactor needs to be kept constant.
96
What do control rods in a nuclear reactor do?
They absorb neutrons without becoming dangerously unstable themselves.
97
True or False: Uncontrolled chain reactions can be dangerous.
True.
98
What is the result of an uncontrolled chain reaction?
A quick increase in the number of reactions due to the rapid increase of available neutrons.
99
What do nuclear fission diagrams illustrate?
They show how the fission reaction occurs in an easy-to-understand way.
100
What is nuclear fusion?
When two light nuclei join to form a heavier nucleus.
101
Where does nuclear fusion take place?
In the centres of stars.
102
What is required for nuclear fusion to occur?
Extremely high temperatures.
103
What is the mass-energy equivalence equation proposed by Albert Einstein?
E = m × c².
104
Fill in the blank: The energy from 1 kg of hydrogen undergoing fusion is equivalent to the energy from burning about ______ kg of coal.
10 million kilograms.
105
What is a valid reason why hydrogen fusion is not currently possible on Earth?
Hydrogen nuclei require very high temperature to fuse together.
106
What is the product of hydrogen fusion reactions?
Helium.
107
True or False: Hydrogen is a rare element in the universe.
False.
108
What is the primary challenge for achieving nuclear fusion on Earth?
Overcoming the repulsive force between positively charged hydrogen nuclei.
