2 atomic structure Flashcards
what is the smallest part of an element
an atom
if atoms are neutral they contain
equal numbers of protons and electrons
relative mass of a proton
1
relative mass of a neutron
1
relative mass of an electron
1/2000
relative charge of a proton
+1
relative charge of a neutron
0
relative charge of an electron
-1
mass number =
equal to the number of protons and neutrons in the nucelus
atomic number =
equal to the number of proton in the nucleus and to the number of electrons in the atom. defines the element
charge of an atom
atoms have no charge so it should be 0, but by losing or gaining electrons they can gain a positive or negative charge
isotopes
atoms that contain the same number of protons but different numbers of neutrons
isotope properties
chemical properties are related to number of electrons so isotopes of the same element have identical chemical properties. since their mass is different, the physical properties like density and boiling point are different
relative atomic mass calculation
isotope A and isotope B
(A abundance x A mass) + (B abundance x B mass)
—————————————————————————–
100
how else can masses be determined
using a mass spectrometer
how do mass spectrometers work
a vaporized sample is injected into the instrument. atoms of the element are bombarded with a steam of high energy electrons in the ionization chamber. in practice the instrument is set so that only ions with a single positive charge are formed. the resulting unipositive ions pass through holes in parallel plates under the influence of an electric field where they are accelerated. the ions are then deflected by an external magnetic field.
what does the amount of deflection in a mass spectrometer depend on
mass of the ion and its charge. the smaller the mass and higher the charge the greater the deflection. ions with a particular mass/charge ratio are then recorded on a detector which measures both the mass and the relative amounts of all the ions present.
three different forms of radiation
gamma
alpha
beta
gamma radiation
highly penetrating
alpha radiation
stopped by a few cm of air
beta radiation
stopped by a thin sheet of aliminium
uses of radiation
nuclear power generation, the sterilization of surgical instruments in hospitals, crime dtection, finding cracks and stresses in food.
which isotope is used for carbon dating
14
C
6
what isotope is used for radiotherapy
131
I
53
what isotope is used as a trcer in medicine for treating an diagnosing illness
125
I
53
trend in size of energy levels surrounding the nucelus
the energy gap between successive levels get increasingly smaller as the levels get further from the nucleus.
sublevels in level 1
1
sublevels in level 2
2
sublevels in level 3
3
sublevels in level 4
4
what is heisenbergs uncertainty principle
“you cannot determine the position and momentum of an electron at the same time”
what is the aufbau principle
“electrons enter the lowest available energy level”
what is pauli’s exclusion principle
“No two electrons can have the same four quantam numbers”, two electrons an go in each orbital, providing they are of opposite sign
what is hund’s rule of maximum multiplicity
“when in orbitals of equal energy, electrons will try to remain unparied.” placing two electrons in one orbital means that, as they are both negativlely charged, there will be some electrostatic repulsion between them. placing each electron in a separate orbital reduces the repulsion and the system is more stable.
what is an orbital
a region in space where one is likely to find an electron
how many electrons can orbitals hold
2 (with opposite spin! (pauli’s exclusion principle) )
orbital s
spherical
orbital p
dumb bell
orbital d
various
orbital f
various
orbital s occurance
one in every principal level
orbital p occurance
three in levels 2 upwards