ch15 - atomic structure Flashcards
pum pudding model of the atom
a model thsat pictured the atom as a positive sphere of pudding with small negatively charged plums embedded in it
JJ Thomson
electron charge
-1.6 * 10^-19 C
nuclear model of the atom
a model that pictures the atom having a very small positively charged nucleus that carries almost all of the mass of the atom surrounded by the much smaller, negatively charged electrons
nucleus
the very small, very dense positively charged centre of an atom
a-scattering experiment
. a particle source encased in metal with a small arpeture (for fine beam of a particles)
. air in apparatus pumped out to leave a vaccum (a-radiation is easily absorbed by few cm of air)
. choosing a gold foil (can be made into very thin sheet)
. a-particles strike a solid scintillating material (give a flash of like, these are counted)
. detector moved around (to detect a particles at different angles)
radius of proton/nuetron
10^-15 m
radius of nucleus
10^-15 m to 10^-14 m
radius of atom
10^-10 m
radius of molecule
10^-10 m to 10^-6 m
mass of proton/neutron
1.67 * 10^-27 kg
mass of eletron
9.11 * 10^-31 kg
volume of sphere
v = 4/3 * pi * r³
density
mass/volume
relative mass
proton - 1
neutron - 1
electron - 0.005
a particle - 4
relative charge
proton => +e
neutron => 0
electron => -e
a particle => +2e
nucleon
a general term to describe the particles in a nucleus (protons and neutrons)
nucleon number
the total number of neutrons and protons in the nucleus of an atom
symbol = A
unified atomic mass unit
one twelfth of the mass of a carbon 12 atom
nuclide
a specific combination of protons and neutrons in a nucleus
isotopes
nuclei of the same element with different numbers of neutrons but same number of protons
hydrogen isotopes
1,1 H - protium
2,1 H - deuterium
3,1 H - tritium
ion
an atom that has lost or gained onefv or more electrons, so that it is electrically charged
strong nuclear force
a fundamental force that acts between particles such as protons and neutrons, but does not affect particles like electrons
. acts over small distances
. holds nucleus together
all elements with proton number > 83
. are unstable
. undergo radioactive decay
more protons
. more electric forces
. more neutrons needed to keep them apart
thus heavy nuclei have neutrons > protons
three types of radiation emitted by radioactive substances
. alpha
. beta
. gamma
where do the three main types of radiation come from
the unstable nuclei of atoms
each radiation’s mass (relative to proton)
a = 4
B- = 1/1840
B+ = 1/1840
y = 0
each radiation’s charge
a = +2e
B- = -e
B+ = +e
y = 0
each radiation’s typical speed
a = slow (10^6 ms-1)
B- = fast (10^8 ms-1)
B+ = fast (10^8 ms-1)
y = speed of light
which types of radiation are particles of matter
a and B
which types of radiation are photons of electromagnetic radiation
y (and x rays)
essentially what is an a particle
He - 4 nulceus
essentially what is an B+ particle
electron
essentially what is an B- particle
positron
which radiation particle has highest penetrating power
y (then B, then a)
a - radiation
. slow moving and large
. very stable (He 2+ ions)
. short range
. not penetrative (lose energy rapidly)
. cause ionisation
B - radiation
. fast electrons
. very small
. charge carrier
. less ionisation
. penetrate further into matter
. occurs when imbalance of p and neutrons (neutron -> p [IF EXCESS decay into neutron, emits positron] + e [expelled])
positron
the antiparticle of the electron, has the same mass as the electron but has a charge +e
beta plus decay
the emission of a positron as a proton decays into a neutron
beta minus decay
the emission of an electron as a neutron decays into a proton
antimatter
material made up of antiparticles of the corresponding particles of ordinary matter
first example of antimatter to be identified
positron
antiparticle + particle =
2 gamma ray photons
which becomes pure energy
example of particle and antiparticle
positron and electron
gamma radiation
. speed in vacuum =3*10^8
. high frequency
. small ionisation
. highly penetrative
. emitted following a/B decay
what is one electronvolt
1 eV is the energy transferred when an electron travels through a potential difference of on volt
what is the value of 1eV
1.6 * 10^-19J
electron antineutrino
an antiparticle that is given off with B- decay with virtually no rest mass and no charge, symbol = ¯v (nu bar)
electron neutrino
a particle that is given off with B+ decay with virtually no rest mass and no charge, symbol = v (nu)
electron neutrino and antineutrino was hypothesised by
Wolfgang Pauli
in radioactive decay is mass conserved
NO, it is lost and turned to kinetic energy
are p, n, e the fundamental particles
NO, there are many other particles that have been discovered by:
. looking at cosmic rays
. looking at the product particles of high energy collisions in particle accelerators
which 2 families are subatomic particles divided into
. leptons
. hadrons
leptons
subatomic particles that are not affected by the strong nuclear force and are believed to be fundamental
lepton examples
. electrons
. neutrinos
hadrons
subatomic particles made up of quarks that are affected by the strong nuclear force
hadron examples
. protons
. neutrons
quarks
fundamental particles that made up hadrons
properties of quarks
. have charges less than fundamental charge
. never found outside hadron
. 6 types (with properties)
types of hadrons
. baryons
. mesons
baryon
. hadrons made up of 3 quarks
. eg. proton (uud), neutron (udd)
mesons
. hadron made up of quarks and antiquarks
. eg pi+ (u¯d)
decay of down quark into up quark in B- decay
d –> u + e- + ¯v
what feels strong nuclear force
hadrons
what feels weak nuclear force
hadrons and leptons
what causes B- decay
hadron –> different hadron + lepton + antilepton
