What is an isotope?
Isotopes are nuclei of the same element with different numbers of neutrons but the same number of protons.
Explain the plum pudding 🍰 model
A model of an atom ⚛ in which negative charges are distributed throughout a sphere of positive charges. (positive pudding 🍰 with negative plums)
Describe the nuclear model of the atom :
A model of an atom in which negative charges (electrons) are distributed outside a tiny nucleus of positive charge.
5 details of the Rutherford experiment
- the alpha particle source was encased in metal with a small aperture, allowing a fine beam of alpha particles to emerge
- Done through a vacuum, so alpha particle is not absorbed by air
- Gold was chosen bec it could be made into a very thin sheet /foil
- The alpha particles were detected when they struck a solid ‘scintillating’ material. Each particle gave a tiny flash of light and these were counted
- The detector could be moved round to detect alpha particles scattered through different angles
From the alpha particle scattering experiment, Rutherford deduced 3 things (NB!!!)
- An alpha particle is deviated due to its repulsive force between the alpha particle and the positive charge in the atom ⚛
- Most alpha particles have little or no deviation - so most of the atom is empty space
- A very few alpha particles are deviated more than 90° - so most of the mass of an atom is concentrated in a small space (the nucleus) and most of the atom is empty space
Where are protons and neutrons situated?
The nucleus of the atom
Protons and neutrons are collectively called?
Nucleons
The total nucleon number in a nucleus is equal to?
The mass number, Ar
Definition of nucleon number or mass number:
The total number of protons and neutrons in the nucleus of an atom
What is the atomic number?
The total number of protons in the nucleus of an atom (also referred to as the proton number)
A (mass number) =
A = N (neutron number) + Z (proton number)
Definition of a nuclide :
A specific combination of protons and neutrons in a nucleus
Definition of a strong nuclear force :
A fundamental force which acts between hadrons
Sub-atomic particles are divided into 2 families, namely :
- HADRONS, such as protons and neutrons. These are particles affected by the strong nuclear force. ( h-heavy in mass)
- LEPTONS, such as electrons. These are particles that are unaffected by the strong nuclear force. (l - light in mass like e-‘s)
Definition of a quark :
The fundamental particles of which hadrons are made of.
can NOT be split further
Quark model of a proton :
uud
Two up quarks and one down quark.
(p are positive so you look more up than down)
The quark model for a neutron :
udd
-one up quark and two down quarks
The 4 types of radiation we learn in AS level :
- a-particle
- B^- particle
- B^+ particle
- Gamma ray
The symbol for an a-particle
a, He
Mass number =4
Proton number =2
Beta minus particle symbol
B^-, e
Mass number 1/1840 (relative to a proton, it is the mass of an electron)
Number of protons =0
Beta plus particle symbol
B^+, e^+
Mass number relative to a proton = 1/1840
Atomic number =0
Gamma ray symbol
Y
No mass or atomic number
Charge on all 4 radiations :
- a-particle = +2e
- B^-= - e
- B^+= +e
- Y= 0
Typical speeds of the 4 types of radiation :
- ‘slow’ 10^6 ms^-1
- ‘fast’ 10^8ms^-1
- ‘fast’ 10^8ms^-1
- ‘speed of light’ 3×10 ^8 ms^-1
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Chapter 7~ Matter And Materials47
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Chapter 8 ~ Electric Fields25
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Chapter 1 : Kinematics - Describing Motion23
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Chapter 2~ Accelerated Motion28
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Chapter 3~ Dynamics - Explaining Motion39
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Chapter 4~forces - Vectors And Moments21
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Chapter 6 ~ Work, Energy And Power ⛮22
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Chapter 6 ~ Momentum18
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Chapter 9~ Electric Current, Potential Difference And Resistance37
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Chapter 10~kirchhoff's Laws23
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Chapter 11~ Resistance And Resistivity22
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Chapter 12~practical Circuits 💫14
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Chapter 13~waves 🌊43
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Chapter 14~ Superposition Of Waves27
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Chapter 15~stationery Waves14
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Chapter 16~radioactivity51
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Practical Skills At AS-level30
