P1- Atomic structure Flashcards
Radius of an atom
1 x 10^-10
Definition of isotopes
Atoms with the same number of protons but a different number of neutrons
Democritus’ Atomic theory (500BC)
Small spheres that make up everything
John Dalton’s ‘solid spheres’ (1800s)
Different solid spheres that are unique to each element
JJ Thompson’s Plum Pudding model (1897)
A ball of positive charge with negative electrons embedded within. An even distribution of charge and mass
Ernst Rutherford’s Nuclear model (1909)
Tried the Gold foil alpha scattering experiment. Found that most of the mass of the atom must be concentrated at the centre in a tiny positively charged nucleas. Most of the atom is empty space.
Niels Bohr’s Planetary model (1913)
Discovered electron shells/energy levels which were fixed distances away from the nucleus
Ernst Rutherford discovery (1913)
Discovered protons which made up a nucleus. All proton particles had the same positive charge adding to the overall charge of the nucleus
James Chadwick discovery (1932)
Proved the existence of the neutron, which explained the imbalance between the atomic and mass number
Where can electrons move in the atom
Within the energy levels
What happens if an atom gains energy by absorbing EM radiation
Move to a higher energy level (further away from nucleus)
What happens if an atom loses energy by releasing EM radiation
Move to a lower energy level (closer to the nucleus)
What is radioactive decay
Unstable isotopes tend to decay into other elements and give out radiation as they try to become more stable
What types of ionising radiation do radioactive substances spit out
Alpha, beta and gamma radiation (or sometimes neutrons)
What is ionising radiation
Radiation that knocks electrons off atoms, creating positive ions
Radiation emission is…
Completely random
What does radiation emission being completely random mean
You can never predict when a sample will decay and give off radiation
How can you approximately predict how many decays emitted from a source over an extended period of time
Calculating its half life
What does ionising mean
How dangerous radiation is