- Chapter 1 and Chapter 3 (exc. 3.1, 3.3, 3.7) Flashcards
Revision for test on Thur 17/10/24
definition of first ionisation energy
The amount of energy required to remove an electron from each of a mole of atoms in the gaseous state.
What is the ionisation energy, compared to the previous one, in successive ionisation energies?
Greater
Trend in ionisation energies going ACROSS a period
Increase as a proton is being added to the nucleus, so there is greater nuclear charge and similar shielding (atom is smaller).
Why do some elements, e.g Al, have lower IEs than the previous element, e.g Mg?
The electron that Al has, which Mg doesn’t, is added to the p-subshell, which has a slightly higher energy level than the s-subshell in Mg, meaning it is easier to lose as it has more shielding due to the s-subshell.
Why do some elements, e.g S, have lower IEs than the previous element, e.g P?
The electron that S has, which P doesn’t, is the first electron that is doubly-paired in the p-subshell. This means that it is easier to lose as it is repelled by the other electron in the pairing.
What is the trend in IE going DOWN the group?
Decreases as the outer electron is in a higher shell, which means it has less nuclear charge and more shielding, which makes it easier to lose.
Electronegativity definition
The ability of an atom to attract electrons towards itself in a covalent bond
what does electronegativity depend on?
nuclear charge, distance of outer shell electron from nucleus and shielding from inner shells
Trend of electronegativity going DOWN a group
Decreases as distance of outer shell electron from nucleus is greater so nuclear charge is less and shielding is greater
Trend of electronegativity going ACROSS a period
Increases as atom has 1 extra proton, which means there is greater nuclear charge and shielding is the same (atoms become smaller)
How many degrees does each lone pair decrease the bond angle by?
2.5
2 bpr, 0 lpr
linear, 180
3 bpr, 0 lpr
trigonal planar
2 bpr, 1 lpr
bent
4 bpr, 0 lpr
tetrahedral, 109.5
3 bpr, 1 lpr
trigonal pyramidal
2 bpr, 2 lpr
bent
5 bpr, 0 lpr
trigonal bipyramidal, 120 and 90
4 bpr, 1 lpr
seesaw
3 bpr, 2 lpr
t-shaped
2 bpr, 3 lpr
linear
6 bpr, 0 lpr
octahedral, 90
5 bpr, 1 lpr
square pyramidal
4 bpr, 2 lpr
square planar
3 bpr, 3 lpr
t-shaped
2 bpr, 4 lpr
linear
Ionisation - electrospray
Sample dissolved in volatile solvent, which is forced through a fine, hollow needle, which is connected to the positive end of a terminal of a high voltage supply, which produces positively-charged droplets that have an extra proton from the solvent. solvent evaporates droplets into the vacuum and they get smaller and smaller until they consist of just one positively-charged ion.
Ionisation - Electron spray
Sample vaporised and high energy electrons are fired at it using an electron gun (hot-wire filament with a current running through it), which knocks off an electron forming a 1+ ion:
X(g) + e^(-) –> X^(+)(g) + 2e^(-)
Acceleration
Positively-charged ions attracted to negatively-charged metal plate, leading them to accelerate towards it. lighter or more highly-charged ions go faster
Ion drift
Ions pass through a hole in the metal plate, concentrating them into a beam and travel along the flight tube
Detection
Lighter ions or more highly-charged ions arrive first and the flight times are recorded. These positively-charged ions pick up (an) electron(s) from the detector, which causes a current to flow
data analysis
current measured by ammeter, which is sent to a computer , which processes the data and generates a mass spectrum.
