P4 Flashcards
What is the size of the radius of an atom?
1×10^-10 m
What is in the nucleus of an atom?
Protons (+) and neutrons (neutral)
What is around the nucleus of an atom?
Electrons (-) In energy levels
How does distance from nucleus affect energy levels?
Energy levels which are further from the nucleus are at higher energy than those close
What happens if an atom, absorbs electromagnetic radiation
An electron can move from a lower energy to a higher energy level temporarily
What is the atomic number and what does it tell us?
23
— Na
11 ————> atomic number
= number of protons,electrons
What is the mass number and what does it tell us?
23 ———> mass number
— Na = number of protons
11. +Neutrons
How do we calculate number of neutrons in an atom?
Mass number - the atomic number
What are isotopes?
Isotopes are atoms of the same element that have different numbers of neutrons
What are ions?
charged Atoms that lost or gained electrons from the outer energy level
What is the plum pudding model?
An atom is a ball of positive charge with negative electrons embedded in it
What is the alpha scattering experiment?
scientist, got a piece of gold foil and fired tiny particles (alpha particles of gold) at it
What did the Alpha scattering experiment tell us?
-Atoms are mainly empty space most alpha particles went straight through the gold
-Due to some of the atoms deflecting atoms must have a positive charge
-Due to some alpha particles bouncing back, the mass of an atom must be concentrated in the centre
What did James Chadwick discover?
The nucleus also contains neutrons
What is radioactive decay?
When an isotope gives out radiation from the nucleus to become stable
What is activity?
The activity is the rate at which is sort of unstable, nuclei decay
1 Bq = 1 decay per second
How do we measure the activity of a radioactive source?
Geiger - muller tube
What is count rate?
The count rate is the number of decays recorded each second by detectors such as Geiger-Müller tube
What are the four types of radiation released by an unstable nucleus?
-Alpha(2 proton 2 neutron)same as helium
-Beta particle (Electron injected from nucleus at very high speed)
-Gamma rays (electromagnetic radiation from nucleus)
-neutron
Where is a beta particle formed?
Inside the nucleus, when a neutron turns into a proton and electron
What is the range in air between alpha particles?
Alpha particles are very large, they travel 5 cm before colliding with air
What is the range in air of beta particles?
Beta particles travel 15cm
What is the range in air between gamma rays?
Gamma rays can travel several metres
What is the penetrating power of alpha particles?
Alpha particles are stopped by a single sheet of paper
What is the penetrating power of beta particles?
Beta particles are stopped by a few millimetre of aluminium
What is the penetrating power of gamma rays?
Gamma rays radiation is stopped by several centimetres of lead
What is the ionising power of alpha particles?
Alpha particles are very strongly ionising
What is the ionising power of beta particles?
Beta particles are quite strongly ionising
What is the ionising power of gamma rays?
Gamma rays are weakly ionising
What is ionising power?
When radiation collides with atoms ,that can cause loss of electrons and form ions
What happens during alpha decay?
Atomic number decreases by 2 mass number decreases by 4
Happens during beta decay
Atomic number increases by one and mass number does not change
What happens during gamma decay?
Nothing both the atomic number and mass number ate not changed
What is a half life?
time taken for
-number of nuclei to decrease by half
-count rate decrease by half
What is irradiation?
Exposing an object to nuclear radiation a good example is sterilisation
What is the risk to humans of ionising radiation?
Ionising radiation can increase risk of cancer
What can we use as shielding (protection) against alpha beta and gamma rays?
For alpha rays, we can use gloves for beta and Gamma rays we can use lead apron and lead
What is radioactive contamination?
When unwanted radioactive isotope end up on other materials
Why is contamination hazardous?
Atoms decay, and emit ionising radiation
What is peer review?
Studies are published in the scientist, allowing findings to be checked for legitimacy
what is an alpha particle
2 charged atoms, 2 neutral atoms
what charge does beta particles have
negative
