3.1 Atomic structure Flashcards
what is the charge of a proton
+1
what is the mass of a proton
1
what is the charge of a neutron
0
what is the mass of a neutron
1
what is the charge of an electron
-1
what is the relative mass of a electron
very small
1/1800
negligible
what composes an atom
proton
neutron
electron `
what is the mass number
the total number of protons and neutrons in an atom
what is found within the nucleus
protons
neutrons
what is the atomic number
the number of protons in the nucleus.
+ number of electrons
how is mass number represented by
A
how is the atomic number represented as
Z
how do you find the number of neutrons in an atom
mass number [A] - atomic number[Z]
what are isotopes
atoms with the same number of protons but different number of neutrons
why do isotopes have similar chemical properties
they have the same electronic structure
why do isotopes have varying physical properties
they have different masses
define Relative Isotopic Mass
the mass off an atom of an isotope compared to 1/12 of the mass of one atom of carbon-12
define relative atomic mass
the average mass of an atom of an element compared to 1/12 of the mass of carbon-12
define relative molecular mass
the average mass of a molecule compared to 1/12 of the mass of one atom of carbon-12
what does the mass spectrometry provide
-gives information about relative isotopic mass
- relative abundance of isotopes
what are the stages of the time of flight mass spectrometry
- Ionisation
- Acceleration
- Ion drift
- ion detection (data analysis)
what is the process of ionisation
turns an atom into an ion
what 2 ways can we ionise an atom
electron impact
electrospray ionisation
what occurs during electron impact
high energy electrons are fired from an electron gun at sample.
This knocks out an outer electron
and forms a positive ion.
what state is the sample in
vapourised
what does electron impact do to a molecule
fragmentation
what is electrospray ionisation
- the sample is dissolved in a volatile solvent.
- This is injected through a fine needle giving a mist.
- Tip of needle has a high voltage
- Sample gains a proton
what is the kinetic energy of the ions when they go through the acceleration
they have constant kinetic energy
how and why do ions accelerate
the plates have a negative charge
the ions accelerate by an electrical field
what type of particle has the fastest velocuty
lightest particle
when the ions accelerates what does it gain
it gains speed and kinetic energy
what is ion drift
when the ions drift down the flight tube within a vaccum
what is ion detection
when the ion hits the detector
- an electron is picked up
- electric current is created
what does the size of the electric current suggest when the ion hits the metal plates ?
the size of the current is proportional to the abundance of the species
what is the nuclear charge
the collective charge of all protons in the nucleus
what does a high nuclear charge mean to the electrons
the electrons are more attracted to the nucleus
what is the trend in the nuclear charge across a period
it increases
what is the trend in the nuclear charge down a group
the nuclear charge increases down the group
what happens to the atomic radius when the nuclear charge increases
the atomic radius decreses
why does the atomic radius decrease when the nuclear charge increases
the shells are closer
what is the relationship between the nucleus and the electrons suggest
the greater the distance between the electron and the nucleus
the weaker the forces of attraction
what happens when the number of shells increases
- the shielding increases
what is the overall trend in the shielding across a period
the shielding stays the same across a period
what is the overall trend in shielding down a period
theres more shielding
and the number of electron energy levels increases
what is the definition of ionisation energy
the enthalpy change when one mole of gaseous atoms form one mole of gaseous 1+ ions.
And electrons are removed
what is the trend in ionisation energy down the group
- decreases down he group
- cause the attraction between the outer electrons and nucleus decreases
why does the attraction between the outer electron and nucleus decrease with the ionisation energy.
- electrons are further away from the nucleus
- more shielding due to the no. of shells
what is the trend in ionisation energy across a period
- increases across the period
- attraction between outer electrons and nucleus increases
why does the attraction between the outer electron and nucleus increase for the ionisation energy across a period
- the nuclear charge increases
- shielding stays the same
why is the ionisation energy of aluminium lower than the ionisation energy of magnesium
-magnesiums outer electron is in the 3s subshell
-Aluminiums outer electron is in the 3p subshell
:. increased shielding and further distance from the nucleus
explain why the ionisation energy of sulphur is lower than that of phosphorus
there is an electron pair in the 3p orbital
so there is greater repulsion
:. less energy is needed to remove the electrons
Explain why the 2nd IE of chlorine is higher than the first IE of chlorine
the 2nd IE of Cl+
is largeer than the 1st IE cause an electron is rremoved from a positive ion which requires more energy
give two reasons why the isotopes are ionised before they can be analysed in a TOT mass spectromemeter. [2 marks]
-so that the ions are accelerated by an electric field towards the negatively charged plates
-ions create a current when the hit the detector, by picking up an electron
basically the debiaitons are the same for periods 2 and 3 in correspondance to the position.
for example the deviaitions of Be and b are the same as the ones of Mg and Al. just swap the 3p orbital to like a 2p orbital.
The deviations of N and O is the same as the ones for P and S
what is the unit for mass in the moles equation
grams
what is the unit for mass in the TOF equation
kg
how are ions detected
+ve ions collide with the detector which causes a current to flow
what is ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
how is abundance is measured
abundance is dependant on the current. its proportional
what deflects the ion
a magnet
what is adjusted in order to direct ions of different mass to charge ratio onto the detector
a magnetic field
name the equipment used to measure the relative abundance of istopes
mass spectrometer
