1.2 - Basic Ideas About Atoms Flashcards
(a)
Atomic structure
**Proton: ** relative mass -1, relative charge - +1
Neutron: relative mass -1, relative charge- 0
**Electron: **relative mass-
negligible, relative charge -1
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Atomic number
number of protons
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Mass number
sum of protons and neutrons
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Isotopes
Atoms of the same element can have different numbers of neutrons. These are called isotopes.
(a)
Alpha (α) particles
positively charged helium nuclei, mass of four units, stopped by a piece of paper, strongly ionising
(a)
Beta (β) particles
Negatively charged electrons, negligible mass, stopped by 0.5 cm of aluminium
(a)
Gamma (γ) radiation
very high energy electromagnetic
radiation, > 2cm of lead required to stop it, weakly ionising.
(a)
Alpha decay (α)
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Beta decay (β)
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Positron emission (β+
decay)
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Electron capture (inverse β decay)
(b)
behaviour of α-radiation in electric and magnetic field and relative penetrating power
α-particles are positive, heavy and slow moving and are attracted slightly to the negative plate
of an electric field.
(b)
behaviour of β-radiation in electric and magnetic field and relative penetrating power
β-particles are light and fast moving and show considerable deviation towards the positive plate of an electric field.
(b)
behaviour of γ-radiation in electric and magnetic field and relative penetrating power
γ-radiation is electromagnetic radiation of short wavelength and is unaffected by an electric
field.