Atomic structure and the periodic table Flashcards
What is relative atomic mass and formula
The mass of an element compared to 1/12 mass of a C12 atom
Ar =( average mass of atom of element / mass of one atom of c12 )
x 12
What do relative isotopic mass and relative molecular mass use instead
relative isotopic mass uses mass of isotope and relative molecular mass uses mass of molecule
As the distance from the nucleus increases how does this affect energy
Higher energy of shells
What is Heinsberg’s uncertainty principle
You cannot say exactly where an electron is if you know its speed
State Aufbau’s principle
electrons enter the lowest energy level first before filling the rest
what is Hund’s rule of maximum multiplicity ?
When two or more orbitals of equal energy (or very close energy) are available, electrons will fill the orbitals singly before filling doubly.
What is the max number of electrons each shell can hold
2n^2 where n = the number of energy levels
What is an atomic orbital
region around a nucleus which can hold up to two electrons with opposite spins
What is an electron ?
Cloud of negative charge
What are the 4 orbitals
- s orbital, spherical shape. Each shell has a single s orbital
- p orbital. dungbell shape. each shell except for first shell has 3p orbitals
- d orbital. various shapes. each shell except first and second have 5d orbitals
f orbital. 7 different f orbitals found in shell 4 and above
What are the three rules for filling atomic orbitals
- orbitals with lowest energy are filled first
- up to two electrons in each orbital if they have opposite spins
- if you have orbitals with same/ close energy you put electrons in individual orbitals first before doubling up
What is the config for copper
1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^1
What is the electronic config for chromium
1s^2 2s^2 2p^6 3s^2 3p^6 3d^ 5 4s^1
Explain the electronic configuration exceptions for chromium and copper
3d sub shell is more stable when completely full or partially full
for Cr if there is only one electron in 4s subshell as opposed to two can have a half full 3d subshell
for Cu by having 1 electron in 4s subshell, can have a completely full 3d subshell
What do groups 1 and 2 of periodic table correspond to
s1 and s2 subshells
What does the transition block of metals correspond to
d1- d10 subshells
What does group 3- 8 of the periodic table correspond to
p1 - p6 subshells
Why are electrons in 4s always lost before 3d ones ?
4s subshell has a lower energy
What is first ionisation energy ?
energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1 + ions
What is second ionisation energy ?
energy needed to remove one mole of electrons from one mole of gaseous ions to form one mole of gaseous 2 + ions
What are the three factors which affect ionisation energy ?
number of protons, atomic radius and shielding
What does shielding refer to ?
electrons in the outer shell are repelled by electrons in the inner shells, so as number of inner shells increases attraction between nucleus and outer shell electrons decreases.
How does number of protons affect ionisation energy ?
electrons are attracted to protons in the nucleus due to opposite charges attracting, so the greater the proton number, the greater the force of attraction between outer shell electrons and nucleus.
This would increase the ionisation energy
How does first ionisation energy vary as you go down a group ?
- decreases as you go down group because the atomic radius increases due to more shells and also more shielding also due to greater shell number. Yes the number of protons increases but this is outweighed by the shielding and more shells. Of
How does first ionisation energy vary accross a period ?
generally increases as you go accross a period. This is due to increasing proton number, which causes electrons to be pulled closer to nucleus, therefore decreasing size of atom ( atomic radius).Because of the same number of shells, shielding effect is the same/ similar.
What are the exceptions to the general increase in ionisation energy across a period ?
from Be to Boron in group 2 there is a drop in ionisation energy. In boron outer electron removed is in a different subshell,2p which has higher energy than 2s subshell ( meaning it is further from the nucleus) so takes less energy to remove outer electron from boron than beryllium- less attraction between p subshell and nucleus.
from N to O another drop in ionisation energy, because in nitrogen each electron is in a separate 2p orbitals while in oxygen one of the orbitals contains an electron pair. An electron in a doubly occupied electron orbital is removed more easily due to repulsion between the two electrons, this requires less energy to remove.
*the 2p sub shell holds up to 6 electrons in 3 orbitals. In nitrogen the 2p sub shell has 1 electron in each orbital. In oxygen, the extra electron has to share an orbital.
What is the use of a mass spectrometer?
To determine the mass number and abundance of isotopes of an element
What is the electron impact method ?
- firstly substance must be vaporised
- high energy electrons knock electrons off atoms to form 1 + ions
electron impact method is used for what kinds of compounds
Low MR compounds
What is the electrospray method ?
- Sample is dissolved in a volatile solvent
- then sample injected through a hypodermic needle which turns sample into a mist
- very high voltage applied to needle tip which causes the sample to become protonated ( gains h + ions) sample becomes ionised
How does a mass spectrometer actually work
Stage 1: Ionization: The atom is ionised by knocking one or more electrons off to give a positive ion. This is true even for things which you would normally expect to form negative ions (chlorine, for example) or never form ions at all (argon, for example). Mass spectrometers always work with positive ions.
Stage 2: Acceleration:The ions are accelerated so that they all have the same kinetic energy.
Stage 3: Deflection:The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected. The amount of deflection also depends on the number of positive charges on the ion - in other words, on how many electrons were knocked off in the first stage. The more the ion is charged, the more it gets deflected.
Stage 4: Detection: The beam of ions passing through the machine is detected electrically. When ions reach detector pick up an electron, flow of electrons causes an electric current. Electric current generates a mass spectrometer.
How does the mass spectrometer figure out mass of isotope
- tine taken to move down drift chamber ( flight tube) used to figure out mass of isotope
- lighter ions travel fastest
How does current produced relate to abundance of isotope ?
- size of current produced used to work out abundance of isotope
more abundant isotope will produce a greater current
What happens as the charge on an ion increases
time taken for it to reach detector decreases
Why is the interior of the spectrometer a vacuum
So that the ions don’t collide with the air molecules
What does the number of peaks tell you on a mass spectrum
the number of isotopes of an element, the higher the peak the greater the abundance of isotope
What is relative isotopic mass
mass of an atom of an isotope compared with 1/12 mass of C12
What is m/z ratio ?
- ratio of mass to charge of isotopes
- usually, ions just have a 1+ charge though so it can basically be considered the mass
what is the ground state of an atom/ion ?
this is the lowest energy arrangement of the electrons in atomic orbitals
- the most stable electron config, where electrons will fill the lowest available energy levels first
