Topic 1-Atomic Structure And Periodic Table And Periodicity Flashcards
Define Relative atomic mass?
The weighted mean mass of an atom of an element compared to 1/12th the mass of a carbon-12 atom
Define Relative isotopic mass
The mass of an atom of an isotope compared to 1/12th of the mass of a carbon 12 atom.
What is the mass spectrometer used for?
The mass spectrometer is a machine which provides chemists with a way to measure and compare masses of atoms and molecules
What are the 5 steps of mass spectrometry?
Vaporisation-heat up molecules so sample turns into gas so individual atoms are separated
Ionisation-An electron gun is used to knock off 1 electron via a collision causing a positive ion to be formed
Acceleration-The positive ions will move towards the negative charged detector
Deflection-A magnetic field deflects the beam of ions e.g. heavier ions will deflect less but lighter will move more
Detection-Ions will detected
Why is a vacuum pump used in mass spectrometry,
To prevent ions from colliding with molecules in the air
Define First ionisation energy?
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1+ ions
What is absorption?
What is emission?
When an electron moves up an electron shell
When an electron moves down an electron shell
What is second ionisation energy?
Energy required to remove 1 mole of electrons from 1 mole of gaseous 1+charge to form 2+ ions
Uses of mass spectrometers?
Determination of RAM of an element
Detection of drugs and their metabolites in urine
In the pharmaceutical industry
What is an orbital?
Region of space outside an atoms nucleus where there there is a high probability of finding an electron with opposite spins
What is the s block?
The s block comprises the elements in groups 1 and 2
The outermost electron is in an S orbital
What is the p block?
Elements in group 3,4,5,6,7,8
Last electron is a p orbital
Why is the 4s orbital below the 3d orbital
The 4s orbital fills below the 3d orbital because it has lower energy
What are the three rules of an orbital
Aufbau principle-electrons go into the orbital with the lowest available energy
Each orbital can only contain 2 electrons with different spins
When there are 2 or more orbitals at the same energy, they fill singly before electrons pair up
What is shielding?
Electron to electron repulsion,repulsion increases energy of the electrons above value they would have had
This decreases nucleur charge
What is Effective nucleur charge?
Net charge on a nucleus,after allowing for the shielding effect of inner electrons
Does effective nucleur charge stay the same down the group?
It does stay the same as increase in proton number(which increases attraction and charge) is outweighed by an increase in electron shielding
Factors affecting energy of an electron?
Radius-greater radius means less ionisation energy as attraction is weaker
Sublevel-an electron from a full or half sublevel requires more energy
Shielding-greater shielding means more ionisation energy
Nucleur charge-amount of protons
Orbital in which they exist
Why are positive ions smaller than its neutral atom?
An ion will lose its outer shell so has fewer electrons and shells
This decreases electron repulsion(shielding) so ENC increases
Increases attractiveness of electrons to nucleus
Why are negative ions larger?
The atom would have gained one or more electrons so repulsion between them increases,attraction between nucleus and electrons decrease so shells move further away increasing atomic radius
What is ionisation energy?
Amount of energy requires to remove an electron from an isolated atom
Ionisation energies keep increasing for an element because..
After the first ionisation energy,positive ions will not want to lose another electron so attractive forces are stronger due to less shielding causing more energy required to break the bonds
More electrons being removed decreases atomic radius which increases attraction so more energy required to remove
Why are ionisation energies of Transition Metals similar?
As you go down from one atom to the next,number of protons increase by 1 so ENC increases but so does the no of 3D electrons
The 3D electrons are most stable half full or fully full so this causes screening
The extra proton and screening cancel out
General trends in ionisation energy?
Atomic number increases,the positive charge of nucleus increases do ENC increases
Ionisation energies increase as you go across a period
Ionisation energies decrease down a group
Why does Ionisation energy decrease down a group?
Nuclear charge increases but this extra attraction is counteracted by a higher atomic radius and shielding so ionisation energy decreases
Why is there a gradual increase in first 6 ionisations of oxygen?
As we remove the first 6 electrons,each of the remaining electrons are pulled closer together so atomic radius decreases so Attraction increases so ionisation energy increases
Why is there an overall increase in ionisation energy across a period?
As we move across a period,each element gains a proton so nuclear charge increases meaning the attraction between positive nucleus and outer electrons increase,and as well as this atomic radius decreases
Why is the some exemptions as to why the ionisation energy across a period does not always increase?
Some electrons are in the 2p subshell and not the 2s so it requires less energy to remove causing a decrease in ionisation energy
Across a period,does atoms increase or decrease in size?
Atoms become smaller so atomic radius decreases and proton no. increases
Do atoms become larger down a group?
Yes,so atomic radius increases and it has a lower electrostatic force of attraction
Why is 2nd ionisation energy endothermic?
This is because incoming electron is already added to a negative ion
Energy is requires to overcome repulsive forces between electron and ion
Explain the effect of low shielding in an atom?
Talk about IE,attraction
Lower shielding means lower electron repulsion,so positive nucleus will have a stronger attraction with outer most electron so electrons are pulled inwards,stronger attraction means more ionisation energy required
Explain and show where the blips occur in ionisation energy across period 2?
Blips occur from group 2 to group 3 and group 5 to group 6
These blips occur as some elements are in the p subshell so there’s more shielding
What is Hunds rule?
When there are 2 or more electrons with same spins,they fill up singly before filling pairs
Why do Isotopes have the same chemical properties?
They have same electronic configuration and have same number of outer electrons which determine chemical properties and reactions
Is Mass Spectrometry,Describe movement of ions in terms of mass and charge?
Ions with greater mass(m/z value)will move less and be deflected less
Ions with greater/multiple charges are deflected more
How to calculate RAM from a mass spectra graph?
1.Multiply RIM(relative isotopic mass when m/z is 1+) by abundance respectively
2.Divide by Total abundance
Explain trends in atomic radius in periods and groups?
Atomic radius decreases across a period as proton no. increases which causes outer electrons to be pulled in as there is a greater attraction between nucleus and outer electrons.
Shielding effect is same across period 2 as all outer electrons are partially shielded by 1 inner electron
Atomic radius increases down a group
