atomic structure Flashcards
describe the process of nuclear fission
a neutron is absorbed by a (large) nucleus
the nucleus splits into two (smaller) nuclei
releasing energy (and gamma rays)
and (two / three) neutrons
describe the process of nuclear fusion
dslj
what is the count rate for a sample that records 769 counts in 60 seconds with a background radiation of 0.3 per second?
769/60 - 0.3
12.5
what is count rate?
counts per second ( recored by a detector eg geiger-muller tube )
what is the radius of an atom?
1 x 10^-10
the radius of a nucleus is less than ______
of the radius of an atom?
1/10,000
how is the energy level of an electron affected by its absorption of electro-magnetic radiation?
the electron will move to a higher energy level, further away from the nucleus
what is an isotope?
atoms of the same element but with a different number of neutrons
how is a mass number determined?
the total number of protons and electrons
how is an atomic number determined?
the number of protons in an atom
before the discovery of the electron how were atoms described?
as tiny spheres that cannot be divided
describe three features of the plum pudding model
- the mass was evenly distributed within the atom
- negative electrons were embedded, like plums in a plum pudding
- the atom was a ball of positive charge
what were three conclusions from the alpha scattering experiment and why?
the mass is concentrated in a very small volume
- most of the particles went straight through so most of the atom is mostly empty space
the mass is concentrated in the centre
- very few came straight back so the mass must be in the centre
and the nucleus was positively charged
- because some were deflected at angles so there must be a concentration of positive charge ( as the positive alpha particles repel other positive charge )
who theorised the idea that electrons orbit the nucleus at different distance?
niels bohr
who discovered the neutron?
james chadwick
