Basic Ideas About Atoms Flashcards
What occurs during radioactive emission?
An unstable nucleus becomes more stable by giving out energy and small particles such as electrons.
Radioactivity is a random process that cannot be influenced by external factors.
Is radioactivity a process that can be stopped or altered?
No, radioactivity cannot be stopped, slowed down or speeded up.
It is dependent only on the nature of the radioactive material.
What are alpha particles made of?
Two protons and two neutrons.
Alpha particles can also be described as helium nuclei (42He2+).
What are beta particles?
Electrons (0-1e) ejected from the nucleus at high speed.
What are positrons?
Anti-electrons (01e) ejected from the nucleus at high speed with a positive charge.
What happens when a positron comes into contact with an electron?
They annihilate each other and create gamma radiation.
What is gamma radiation?
High energy electromagnetic radiation emitted during the rearrangement of a heavy nucleus into a more stable configuration.
What is electron capture?
A process where a proton-rich nucleus absorbs an inner electron, combining it with a proton to form a neutron.
How do alpha particles behave in an electric field?
They are weakly attracted to the negative plate due to their positive charge.
How do beta particles behave in an electric field?
They show considerable deviation towards the positive plate due to their light and fast-moving nature.
How does gamma radiation interact with an electric field?
It is unaffected due to its nature as electromagnetic radiation of short wavelength.
What can stop alpha particles?
A single sheet of paper or the outer layer of human skin.
What can stop beta particles?
A thin layer of metal such as aluminium foil.
What can stop gamma radiation?
A thick plate (2 cm or more) of a highly dense metal such as lead.
Which particles are the most ionising?
Alpha particles.
They remove electrons from atoms due to their high positive charge.
How do beta particles ionise atoms?
By colliding with electrons in atoms, knocking them out.
What is the least ionising type of radiation?
Gamma radiation.
What is half-life?
The time it takes for the count-rate (or mass) of a radioactive substance to fall to half of its original value.
What is first ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
What is second ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.
What affects the pull on electrons in a nucleus?
The number of protons in the nucleus.
What is the role of inner electrons in atomic attraction?
They interfere with the attraction between the nucleus and the outer electron.
What are energy levels in an atom?
Regions of space around the nucleus where there is a high probability of finding an electron of a particular energy, called orbitals.
What is the filling order for the first 36 elements?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p.
What is special about chromium and copper in terms of electron configuration?
They have half-filled or filled 3d-orbitals and only one electron in the 4s orbital.
What is an emission spectrum?
A series of lines that correspond to particular frequencies of energy emitted by an excited species.
What is the Balmer series?
Emission lines corresponding to the transition of an electron falling back into the n=2 energy level, producing visible light.
What happens when an excited electron falls back into the n=1 energy level?
The energy of light emitted is in the ultraviolet part of the electromagnetic spectrum.
What is the convergence limit in spectral lines?
The frequency at which the spectral lines become closer together as the radiation frequency increases, corresponding to ionisation energy.
