atomic structure Flashcards
define atomic number
is equal to the number of protons
define mass number
equal to the number of protons and neutrons combined
cations
lost electrons
positive ions
anions
gained electrons
negative ions
define isotopes
same number of protons but different number of neutrons
why do isotopes have the same chemical properties
they have the same electron configuration
what is the relative mass and charge of a proton
1 and +1
what is the relative mass and charge of neutron
1 and 0
what is the relative mass and charge of electron
1/1840 and -1
define ionisation energy
the amount of energy needed to remove one mole of electrons from a mole of atoms in the gaseous state
explain a small jump in successive ionisation energies
removed from a ore positive ion
explain a big jump in successive ionisation energies
there on different shells closer to the nucleus so less shielding
what shape does a s orbital have and how many sub shells are there in it
spherical shape
one s orbital
what shape does a p orbital have and how many sub shells are there in it
dumbbell shape
3
what shape does a d orbital have and how many sub shells are there in it
three p orbitals
5
why electron on an atom has the highest energy
outer most electron because i is furtherest from the nucleus
what are the exceptions to electron configurations
chromium (more stable if 3d is exactly half full)
copper (more stable if 3d is full)
what is the trend in IE across period 3 and why
general increase
there is a greater nucleus charge across period 3
same amount of shielding
so greater attraction between the nucleus and outer electron
explain why Al has a lower 1st IE than magnesium
the first e- removed from Mg is from a 3s sub shell
the first electron removed from Al is from a 3p sub shell
the 3s sub shell is lower in energy than 3p
therefore less energy is needed to remove the electron from Al
explain why S has a lower 1st IE then Phosphorous
the first e- removed from p is from a 3p sub shell and is unpaired
the first e- removed from s is also from a 3p sub shell but is from a paired orbital
this means s has a lower IE due to electron pair repulsion
therefore less energy is needed to remove the electron from s
how does the ionisation energy change down a group
atoms get bigger
more shielding
weaker attraction from nucleus to electron in outer shell
ionisation energy decreases down group
state and explain the trend in atomic radius down a group
atomic radius increases
the number of shells increases so the amount of shielding increases
why does the atomic radius gets smaller from right to left across a period
the nuclear charge increases
there is a greater attraction between the electrons and the nucleus the amount of shielding stays the same
briefly outline how a time of flight mass spectrometer works
an unknown mixture is injected into a mass spectrometer, it is converted into positive ions, accelerated to high speed, and then arrived at a detector
describe the vacuum
the entire machine is a vacuum inside to prevent an of the particles being tested colliding with molecule from the air
what are the 2 types of ionisation
electron impact
electrospray
describe acceleration
the positive ions attracted to a negatively charged plate and accelerate towards it
once accelerated all ions will have same kinetic energy
describe ion drift
particles travels t different speeds
describe detection
this generates a current the size of which is proptional to the number of each type of ion
how are ions detected
each ion hits the detector
ions gain an electron
generates a current
size of current is proptional to the abundance of the ion
how are ions separated in the flight tube
ions travelling at higher speeds (small m/z) move ahead of those travelling at more slow speeds (large m/z)
describe electron impact ionisation
the sample is vaporised and then high energy electrons are fried at it
the high energy electrons come from an electron gun which is a hot wire filament with a current running threw it that emit electrons
this knocks of one electron forming a 1+ ion
describe electrospray ionisation
the sample is dissolved in a volatile solvent and injected through a fine hypodermic needle to give a fine mist
the tip of the needle is attached to the positive terminal of a high voltage power supply
the particles are ionised b gaining a proton
which ionisation technique is fragmentation more likely to take place
electron impact ionisation
kinetic energy equation
Ke = 1/2 mv^2
what is equation for time of flight
t= d/v
calculating mass from mr
mr divde by thousand divde by avogadro constant
