Atomic Structure Flashcards
Mass of proton
1
Mass of neutron
1
Mass of electron
1/1800
Charge of proton
+1
Charge of neutron
0
Charge of electron
-1
Atomic number
number of protons in the nucleus
Mass number
Total number of protons and neutrons
Isotopes
Atoms with the same number of protons but different number of electrons
Reason mass spec is done under a vacuum
Otherwise air particles would ionise and be detected
Steps of mass spec
Ionisation, acceleration, drift, detection
Electron impact ionisation
High energy electrons are fired at a vaporised sample removing an outer electron forming positive ions
Electrospray ionisation
Sample is dissolved in a volatile, polar solvent and injected through a fine needle. The tip of the needle has a high voltage adding a proton to the sample. M(g) + H= –> MH+
Use of electron impact
elements and substances with low formula mass. Larger molecules may fragment
Use of electrospray ionisation
larger organic molecules as fragmentation is less likely
Acceleration
Positive ions are accelerated by an electric field to a constant kinetic energy = 1/2 m v2
Flight Tube/ Drift region
Lighter ions move down the tube quicker than heavier ones and are distinguished by flight times
Detection
positively charged ions are attracted to a negatively charged plate generating a current, which a computer analyses. The more ions of a particular size, the larger the current produced
Relative atomic mass
weighed average of all isotopes of an atom compared to 1/12th mass of a C-12 atom
Relative atomic mass calculation
(mass 1 x abundance 1) + (mass 2 x abundance 2) + … / total abundance
What is the relative atomic mass for Mg?
Mg-24 = 78.70%, Mg-25 = 10.13%
Mg-26 = 11.17%
24.3
Key features to include when asked for species for a peak on a mass spectrum
charge and mass number. e.g. 24Mg+
Calculate the relative atomic mass of Te. Te-124 = 2, Te-126 = 4, Te-128 = 7, Te-130 = 6
127.8
Copper has 2 isotopes 63-Cu and 65-Cu. The RAM is 63.5. What is the abundance of each isotope
63-Cu = 72.5% 65-Cu = 27.5%
Molecular Ion Peak
Shows the relative molecular mass and is the peak furthest to the right
Order sub shells are filled –> 5p
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p
Electronic structure for Ca
1s2, 2s2, 2p6, 3s2, 3p6, 4s2
s block element
element with highest energy electron in an s sub shell (first two groups of PT)
p block element
element with highest energy electron in an p sub shell (end 6 groups of PT)
d block element
element with highest energy electron in an d sub shell (central section of PT)
electronic configuration for Sc
[Ar] 4s2, 3d1
electronic configuration for Ti
[Ar] 4s2, 3d2
electronic configuration for V
[Ar] 4s2, 3d3
electronic configuration for Cr
[Ar] 4s1, 3d5
electronic configuration for Mn
[Ar] 4s2, 3d5
electronic configuration for Fe
[Ar] 4s2, 3d6
electronic configuration for Co
[Ar] 4s2, 3d7
electronic configuration for Ni
[Ar] 4s2, 3d8
electronic configuration for Cu
[Ar] 4s1, 3d10
electronic configuration for Zn
[Ar] 4s2, 3d10
electronic configuration for Ti3+
[Ar] 3d1
electronic configuration for V3+
[Ar] 3d2
electronic configuration for Cr3+
[Ar] 3d3
electronic configuration for Mn2+
[Ar] 3d5
electronic configuration for Cu2+
[Ar] 3d9
electronic configuration for Zn2+
[Ar] 3d10
Rules for filling orbitals
Fill lowest energy orbitals first. Singly fill orbitals before doubly filling
Rules for filling and emptying d block element sub-shells
Fill 4s before 3d. Empty 4s before 3d.
First Ionisation Energy
Energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
Equation for first ionisation energy
X(g) –> X+(g) + e
Second Ionisation Energy
Energy required to remove one mole of electrons from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
Second ionisation energy equation
X+(g) –> X2+(g) + e
Factors that affect ionisation energy
Amount of protons, distance of electrons from nucleus and amount of shielding
Why are successive ionisation energies always larger?
2nd IE is larger than 1st IE because the electron is being removed from a 1+ ion with greater attraction to the outgoing electron.
What does a big jump in successive ionisation energy show?
A change of shell that the electron is being removed from. E.g. a big jump from electron 4 to 5 indicated the element is in group 4 with 4 electrons on the outer shell
What group is this element in? 1st IE = 590 2nd IE = 1150 3rd IE = 4940 4th IE = 6480 5th IE = 8120
Group 2
How does IE change down a group?
Decreases - despite having more protons, the elements have a greater distance from the nucleus to the outgoing electron with more shielding
What is the general trend in IE across a period
Increases - successive element have more protons but the electrons are added to the same shell with the same amount of shielding and slightly less distance between the outer shell and the nucleus
Why is there a drop in IE from Mg to Al?
The outermost electron in Al is in a 3p orbital compared to 3s in Mg so is slightly further away from the nucleus with more shielding so easier to remove.
Why is there a drop in IE from P to S?
The outermost electron in S is in a paired 3p orbital compared to singly filled 3p in P. This means there is some repulsion from the other electron making it easier to remove.
