atomic structure (1) Flashcards
what is inside the nucleus
protons and neutrons
relative mass & relative charge of a proton
1 & +1
relative mass & charge of a neutron
1 & 0
relative mass & charge of an electron
1/2000 & -1
how did john dalton describe the atom
atom was the smallest particle & indivisible
how did JJ Thompson describe the atom & what did he discover
discovered: electron
described the atom as a positive charge spread through with negative electrons dispersed
how did Ernest Rutherford describe the atom and how did he come to this conclusion
bombarded alpha particles at thin gold foil and some bounced back, discovering the nucleus and describing the atom as a tiny positive nucleus surrounded by mainly empty space in which electrons are moving
What did Neils Bohr discover and how did he describe the atom
as rutherford, but electrons moving in energy levels. he discovered electrons move in shells (energy levels)
how did james chadwick describe the model
As Bohr, but nucleus contains protons and neutrons
what type of mass spectrometer do we use
time of flight mass spectrometer
explain how mass spectrometry works
- ionised by either electron impact or electrospray ionisation
- the positive ions are accelerated using an electric field
- the positive ions travel through a hole in the negatively charged plate into a tube
- the positive ions hit a negatively charged plate.
- current is produced
ions with the same charge have the same _________
kinetic energy
will lighter ions be faster or slower than heaver ions when drifting towards the detector
faster velocity
how do you determine the mass of the isotope using the mass spectrometer
the time taken for the isotope to reach the detector determines the mass of the isotope
how do you determine the abundance of the isotope using the mass spectrometer
the size of the currentproduced when the isotope hits the detector
what is the interior of the mass spectrometer made out from
vaccum to prevent ions colliding with molecules in the air.
why must a sample containing isotopes must be vaporised and ionised
to make it acclerate, to detect the ions.
define mass number
the number of protons and neutrons
define relative atomic mass
average mass of 1 atom compared to 1/12 the mass of 12C
one change in the operation of the mass spectrometer that will change the velocity of an ion
electric field
why is the value calculated on the mz graph thing different from the relative atomic mass given in the periodic table different
because the Ar in the periodic table takes account other isotopes
why do isotopes of an element have the same chemical properties
because they have the same electron configuration
how are ions formed in a time of flight mass spectrometer
electrospray ionisation or electron gun
what is ionisation energy
ionisation energy is the minimum energy required to remove the most loosely bound electron
name 3 factors that effect ionisation energy
atomic radius, number of protons, shielding
how does atomic radius effect ionisation energy
the smaller the radius the stronger the attraction between the nucleus and electron, so ionisation energy increases
how does number of protons effect ionisation energy
the more protons the stronger the attraction between the nucleus and electrons, meaning higher ionsiation energy
how does shielding effect ionisation energy
more shielding means the weaker the attraction between nucleus and electron, so the ionisation energy is decreased
how and why does ionisation vary when going down a group
electron is easier to remove as there is weaker attraction between the nucleus and electron, so ionisation energy decreases
(there is more shielding and a bigger atomic radius)
how and why does ionisation vary when going across a period
general increase across period
because:
-smaller atomic radius
-more protons
-stronger attraction between nucleus and electron
-electron more difficult to remove
what does electronegativity mean
ability of an atom to attract electron density
what does first ionisation energy mean
the energy required to remove 1 mole of electrons from 1 moles of gaseous atoms to form 1 mole of gaseous 1+ ions
what is electron impact
high energy electrons fired at the sample from electron gun
what is electrospray ionisation
- sample is dissolved in a volatile solvent
-then injected through a needle at high voltage
-each particle gains H+
what happens when an ion hits the detector
the ion loses an electron
equation for mass (kinetic energy)
m = 2KET² / D²
equation for time (kinetic energy)
t = d x √m / 2KE
equation for distance (kinetic energy)
d = t x √2KE / m
what is adjusted so that each isotope can be detected
electric field
how does adjustment enable isotopes to be separated
deflection depends on mass or m/z
how can the mr be obtained from its mass spectrum
the mr is the highest mz value
what is used to deflect the positive ions
magnetic field
why does ionisation energy drop at 2-3
outer electron is further from the nucleus and is higher in energy, so electron is easier to remove
why does ionisation energy drop at 5-6
if in the orbital, electron from, 2 electrons need to pair and the pairing will cause repulsion.
meaning of atom
smallest part of an element that can exist
meaning of atomic nucleus
positively charged object composed of protons and neutrons at the center of every atom with one or more electrons orbiting it
meaning of atomic number
number of protons in the nucleus
meaning of electron
negatively charged subatomic particle which orbits the nucleus at various energy levels. relative mass of 1/2000
meaning of electron configuration
the distribution of electrons of an atom in orbitals
meaning of isotope
atoms of the same element with same number of protons but different number of neutrons
mass number meaning
total number of protons and neutrons in the nucleus
mass spectrometer meaning
a mass spectrometer gives accurate info about relative isotopic mass and also about the relative abundance of isotopes
mass spectrometry meaning
mass spec can be used to identify elements and determine relative molecular mass
neutron meaning
neutral subatomic particle present in the nucleus of the atom
nuclear charge meaning
total charge of all the protons in the nucleus.
proton meaning
positively charged subatomic particle present in the nucleus of the atom
sub- shells meaning
electron shells are divided up into sub-shells which have slightly different energy levels. the sub shells have different numbers of orbitals which can each hold up to two electrons
Which one of the following is a fundamental particle that would not be deflected by an electric field
neutron
Explain why the second ionisation energy of boron is higher than the first ionisation energy of boron
because the electron is closer to the nucleus and requires more energy to remove
What is the maximum number of electrons that can be accommodated in an s sub-level?
2
how are ions detected in the TOF
by gaining electrons
