3.1.1 ATOMIC STRUCTURE Flashcards
What equation gives the maximum number of electrons that a main energy level can hold?
2n^2
What is the name of the number given to each shell?
A principle quantum number (n)
1st shell = principle quantum #1
What are atomic orbitals?
A region around the nucleus that can hold up to two electrons with opposite spins
(Electrons can have an up or down spin)
What is the rule for electrons in the same orbital
They must have opposing spins
What is the shape of an electron as a negative cloud of charge?
The shape is that of the orbital it occupies
What is a subshell
A subshell consists of all of the orbitals of the same type in the same shell
What is the relationship between the distance of a subshell from the nucleus and it’s energy?
As the distance increases, the energy of the subshells increases
What are the rules for filling atomic orbitals?
- Orbitals with the lowest energy levels are filled first
- 2 electrons are allowed in each orbital but they must
have different spins - If orbitals with the same energy are present, then they
fill up into individual orbitals before pairing up to avoid
repulsion (from being in the same orbital)
How should mayowa draw arrows when representing electron spin? (for AQA spec)
As a reversible reaction arrow flipped 90degrees
Why does electron configuration not show individual orbitals?
It only shows the subshell, not the individual orbitals
What is the anomaly in the filling order of atomic orbitals?
The 4s subshell contains less energy than the 3d orbital, and therefore fills up first
What is the electron configuration of Iron (Z=26)
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6 WOULD BE WRONG
1s2, 2s2, 2p6, 3s2, 3p6, 3d6, 4s2 tick
What rule should be followed when writing configurations of atoms containing above 3d orbitals?
The configuration is written in the order of electron shells and not filling, so 3d comes before 4s
Expected electronic configuration of chromium vs actual configuration (Z = 24)
1s2, 2s2, 2p6, 3s2, 3p6, 3d4, 4s2
1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1 - Actual
- 3d subshell is more stable when half or completely
full
Expected electronic configuration of Copper vs actual configuration (Z = 29)
1s2, 2s2, 2p6, 3s2, 3p6, 3d9, 4s2
1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1 - Actual
- 3d subshell is more stable when half or completely
full
What is the significance of the names of different blocks in the periodic table?
Each block is names after the highest energy electron for the elements in that block
What should be noted when using a periodic table for configuration par rapport a d block
The first row of the d block represents electrons in the d subshell in the third energy level, however the 4s subshell fills before the 3d subshell
What electrons are involved in chemical reactions?
The outer shell
What is the shorthand method for electron configuration?
Use Na (Z=11) as an example
Find the position of Sodium in the periodic table
Find the position of the first noble gas before it (Neon, Z =10)
- Add on remaining electrons e.g 3s1
Neon = 1s2,2s2,3p6
Sodium = 1s2,2s2,3p6,3s1
Write shorthand electron configurations for Be, S, Ca and Mn
Be = [He] 2s2
S = [Ne] 3s2, 3p4
Ca = [Ar] 4s2
Mn = [Ar] 3d5,4s2
Why is the d subshell still shown in the shorthand configuration of elements even if they aren’t in the outer shell?
Electrons in the d subshell can still be involved in chemical reactions
4s and 3d subshell lore
The 4s subshell contains less energy than the 3d subshell, and therefore fills up first, however once the 4s shell is filled, it has more energy than the 3d subshell, so when d block elements lose electrons, they are lost from the 4s subshell before the 3d subshell (No exceptions)
What is the electron configuration of a manganese (Mn 3+) ion?
1s2,2s2,2p6.3s2,3p6,3d4
What is the definition of FIRST ionisation energy?
The energy [KJ/Mol] required to remove ONE MOLE of electrons from ONE MOLE of an atom in its GASEOUS STATE to form ONE MOLE of +1 IONS in their gaseous state
Define successive ionisation energy
The amount of energy [KJ/Mol] to remove ONE MOLE of electrons from ONE MOLE of n+ ions to form ONE MOLE on (n+1) + ions (all in gaseous state)
What are the factors affecting ionization energy?
- Atomic radius
- Charge on the nucleus
- Shielding - electrons on outer shells repelled by inner
shells, reducing the attraction between the nucleus
and outer electrons
Why does ionization energy increase as an atom loses more electrons?
Every time an electron is removed, the remaining are pulled slightly closer to the nucleus
Why does ionization energy increase between main energy levels?
As electrons are closer to the nucleus therefore experience a greater electrostatic attraction + less shielding
How does ionization energy change down a group?
- Decreases
- Greater atomic radius + greater shielding due to more
internal energy levels - this offsets the increase in nuclear charge
How does ionization energy change across a period?
- Increases
- Greater nuclear charge, increases attraction between
nucleus and electrons (Greater force for the same
shielding effect) - Decreases atomic radius
- Outer electrons are more attracted to the nucleus
(greater amount of energy required to remove)
Why does Boron have a lower first ionization energy than Beryllium, despite being further along period 2?
- Boron’s outer electron is in the 2p subshell, while
Beryllium’s is in the 2s subshell. - As the 2p subshell has more energy, less is required
to remove a valence electron
[FIRST IONIZATION]
Why does Oxygen have a lower first ionization energy than Nitrogen, despite being further along period 2?
- Both elements’ outer electrons are in the 2p subshell
- However oxygen has a pair of electrons in the same
orbital, which repel - So less energy is required to remove that electron
Describe s, p and d orbitals
- S orbitals can hold up to 2 electrons with opposite
spins - P orbitals can hold up to 2 electrons, and 3 can exist
at the same main energy level (6 in total) - D orbitals can hold up to 2 electrons, and 5 can exist at the same main energy level (10 in total)
Write the equation for the first 3 successive ionisation energies of Sodium
- Na(g) —- Na(g)+ + e-
- Na+(g) ——- Na2+(g) + e-
- Na2+(g) ——- Na3+(g)+ e-
(The first ionization energy of Na [494kj/mol] is sneakily close to the bond energy of an O=O bond[498])
The Ne atom and the Mg2+ ion have the same number of electrons. Give two
reasons why the first ionisation energy of neon is lower than the third ionisation
energy of magnesium.
- Mg2+ ion smaller than Ne atom / Mg2+ e-
closer to nucleus - Mg2+ has more protons than Ne / higher nuclear
charge or e- is removed from a charged Mg2+ion
Why would an element be classified as a P block element?
Because its outer electrons reside in p orbitals
Why do isotopes of an element react in similar ways?
They have the same electron configuration
Describe how a time of flight spectrometer works
- Sample is vapourised and placed into a chamber
(Sample contains all different isotopes of element) - Electrons are fired at sample, turning all sample
atoms into positive ions - Positive ions are now attracted to a cathode (neg)
- Ions accelerate, increases the Ek of the ions
- Ions with the same charge have the same Ek
- Ions past through cathode and stop accelerating
- Ions drift down the chamber towards a detector
- Smaller ions move faster than heavier ones (inertia)
(Same electrostatic force) - Each ion gains electrons from the detector
(A 1+ ion gains 1 electron) - Transfer of electrons causes a current to flow
- Time taken for an ion to drift down the chamber is
used to determine its mass - Size of current produced when each isotope hits the
detector is used to determine abundance - a more
abundant isotope produces a greater current
Describe the interior of a TOF mass spectrometer and its purpose
It is a vacuum, to prevent ions colliding with air molecules
What is the principle behind a mass spectronomer?
Forming ions of a sample, and separating them by the ratio of their mass to their charge
What is m/z ratio?
The mass to charge ratio (for an ion)
For a 1+ ion the m/z ratio is its atomic mass
Describe the process of electron impact ionisation
The sample being analysed is vaporised and then high energy electrons are fired at it. The
high energy electrons come from an ‘electron gun’ which is a hot wire filament with a current
running through it that emits electrons. This usually knocks off one electron from each
particle forming a 1+ ion.
What is the equation for electron impact ionisation?
X(g) + e- —- X+(g) + 2e-
Also written as
X(g) —– X+(g) + e-
What types of compounds/substances is electron impact ionisation used for?
Ones with low formula masses, e.g. Methane
When molecules are ionised in this way, they are called molecular ions. The molecular ion often breaks down into smaller fragments some of which are also detected in the mass spectrum
Describe the process of electrospray ionisation
Sample is dissolved in a volatile solvent (eg water or methanol) and injected through a
fine hypodermic needle to give a fine mist. The tip of the needle is attached to the positive terminal of a high-voltage power supply. The particles are ionised by gaining a proton (H+) from the solvent as they leave the needle producing
XH+ ions. The solvent evaporates from the droplets into the vacuum and the droplets get smaller and smaller until they may contain no more than a single positive ion
What is the equation for electrospray ionisation?
X(g) + H+ —– XH+(g)
What types of compounds/substances is electrospray ionisation used on?
Substances with higher molecular mass e.g. proteins. This is known as a ‘soft’ ionisation technique and
fragmentation rarely takes place.
