Atomic Structure Flashcards
What is the timeline for the discovery of the atom.
Democritus>John Dalton>J.J Thompson>Rutherford>Niels Bohr>James Chadwick
What did Democritus do?
-He discovered that atoms are in a spherical shape and are indivisible
What did John Dalton do?
He described atoms as solid spheres and said that different spheres made up the different elements
What did JJ Thompson do?
He made the plum pudding model(ball of positive charge with negatively charged electrons) and concluded that an atom must contain even smaller, negatively charged particles.
What did Rutherford do?
He did the alpha scattering experiment.He fired alpha particles at a very thin sheet of gold. From the plum pudding model, he expected most of the alpha particles to be deflected slightly by the positive ‘pudding’ that made up most of the atom.
What were the results of Rutherford’s model?
Most of the alpha particles passed straight through the gold atoms and a very small number were deflected backwards
What did the results of Rutherford’s experiment show him?
There’s a tiny, positively charged nucleus at the centre surrounded by a ‘cloud’ of negative electrons
Most of the atom is empty space
What did Niels Bohr do?
He discovered electron shells
What did James Chadwick do?
Discovered neutrons
What is the relative mass of protons, neutrons and electrons
p:1
n:1
e:1/1840
What is the charge of protons, neutrons and neutrons electrons?
p:+1
n:0
e:-1
What is an isotope?
Atoms of the same size element that contain different numbers of neutrons
What can be said about the reactivity of different isotopes of an element?
The reactivity is identical because they have the same number of electrons
What is the isotope abundance of chlorine-35
75%
What is the isotope abundance of chlorine-37
25%
Define the relative atomic mass
The average mass of its atoms, compared to 1/12th the mass of a carbon-12 atom
What is the percentage abundance of bromine?
50%
How does ionisation work with an electron gun in a ToF
high energy electrons from the gun knock off an electron from each particle in the sample(gas). The particles form a positive charge
What is the ionisation equation for zinc, water and chlorine
Zn(g)->Zn(g)++e-
H20(g)->H20(g)++e-
Cl2(g)->Cl2(g)++e-
How does ionisation work with an electron spray in a ToF
The sample (a solution) is put through a hypodermic needle attached to a positive terminal of high voltage power supply.
The pericles gain a proton as they leave the needle spread out in a fine mist because the +ively charged particles are all repelling each other
Which type of ionisation method is used for large compounds and which are used from small molecules
Electron gun- small molecules
Spray- large compounds
What are the 4 stages in a ToF
1.ionisation
2.acceleration
3.drift region
4.detector
What happens in the acceleration stage?
the positively charge particles are accelerated towards the negatively charged plate
every single particle has the same kinetic energy however lighter particles travel faster as they have a higher velocity
this means that lighter particles get to the detector first
what is the equation for kinetic energy
1/2mv^2
What happens during the drift region
After the particles have been through acceleration, they pass through a hole in the negatively charged plate and travel through the region at different speeds until they reach the negatively charged detection plate
What happens at the detector
Once the positive ions reach the negatively charged detection plate, they gain an electron and produce a current
The size of the current is proportional to the abundance
What is the electron structure of Krypton(it has the atomic mass of 36 which is the largest number you need to know)
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
What are the 2 anomalies you need to know regarding electron configuration
chromium and copper
How are copper and chromium anomalies regarding (electron configuration)
The ‘3d orbital’ is filled up first before the ‘4s orbital’
what is the electron structure of chromium(atomic number 24)
1s2 2s2 2p6 3s2 3p6 4s1 3d5
what is the electron structure of copper (atomic number 29)
1s2 2s2 2p6 3s2 3p6 4s1 3d10
What is the definition of 1st ionisation energy
The energy needed to remove one mole of electrons from one mole of atoms in their gaseous state to form one mole of 1+ ions(also in their gaseous sate)
What are the factors that decide ionisation energy down a group?
Number of protons
Distance from the nucleus
Shielding
How does the number of protons that an atom has affect ionisation energy?
The protons and atom has, the higher the nuclear charge, so the higher the ionisation energy.
How does shielding affect ionisation energy?
The more shells an atom has, the easier it is tk remove an electron so the lower the ionisation energy
How does the distance from the nucleus affect ionisation energy?
The further away the outer shell electron is from the nucleus the easier it is to leave the atom.
Out of lithium, sodium and potassium, which atom has the highest ionisation energy and why?
Lithium. It has the least amount of shielding and the smallest distance between the outer electron and nucleus. This means that there’s a stronger force of attraction between the nucleus and outer shell electron, so the electron is harder to lose so will require the most amount of energy
Is the second ionisation energy larger than the first? Why/why not
Yes it’s larger. When an atom loses an electron and goes through the second ionisation, the shell gets tighter and the and the atom gets smaller so the 2nd ionisation energy energy is larger than the 1st because the electron will be harder to remove as the distance between the outer shell and nucleus is smaller.
What are the factors that decide ionisation energy across a period?
Number of protons
Shielding
Distance
FoA
What is the general trend regarding ionisation energy across a period
Increase in ionisation energy across a period.
As you go across a period, the proton number gets bigger so the atom gets smaller because the nucleus has a greater charge and the outer electron is more attracted to the nucleus
What are the exceptions to the increase in ionisation energy across a period trend?
Movement from s-orbital to p-orbital
Movement from 3 electrons in the p orbital to 4 electrons
How is the movement from s-orbital to p-orbital an exception to the general trend regarding ionisation energy across a period?
p orbital is a higher energy level compared to s orbital so the outer shell electron is further away from the nucleus so there’s a weaker force of attraction which makes it easier to lose the electron so there’s lower ionisation energy
How is the movement from 3 electrons in the p block to 4 electrons an exception to the general trend regarding ionisation energy across a period?
When there are 4 electrons in the p block instead of 3, 2 electrons have to be in the same orbital so they repel each other which means it takes it takes less energy to remove the electron.
What is the the electron structure of (transition metal) ions
Remove the electrons from the s block first before the d block
What is the electron structure of Fe2+
1s2 2s2 2p6 3s2 3p6 3d6
Between argon and postassium, which atom has the greatest first ionisation energy
(Ar:1s2 2s2 2p6 3s2 3p6
K:1s2 2s2 2p6 3s2 3p6 4s1)
Argon. Argon has fewer energy levels compared to potassium. Argon has a smaller atomic radius and has less shielding so the outer shell electron is closer to the nucleus so there is a stronger force of attraction and a higher ionisation energy
Between magnesium and calcium, which atom has the greatest first ionisation energy
(Mg: 1s2 2s2 2p6 3s2
Ca: 1s2 2s2 2p6 3s2 3p6 4s2)
Same group
Magnesium has a smaller atomic radius and less shielding so the outer shell electron is closer to the nucleus which means there’s a greater force of attraction that will take more energy to break
Between sodium and magnesium , which atom has the greatest second ionisation energy
(Na+: 1s2 2s2 2p6
Mg2+: 1s2 2s2 2p6 3s1)
Sodium. Sodium has a smaller radius and smaller shielding so the outer shell electron is closer to the nucleus which is harder to remove so requires a higher ionisation energy.
Between phosphorus and sulphur , which atom has the greatest second ionisation energy
(P+: 1s2 2s2 2p6 3s2 3p2
S-: 1s2 2s2 2p6 3s2 3p3)
Sulphur.
Sulphur has more protons and a smaller radius so there is a greater force of attraction between the outer electron and nucleus which makes it harder to break which means there is a greater ionisation energy.
Why is the mass spectrometer kept under vacuum?
to prevent the ions produced from colliding with molecules that would be in the air
what two pieces of information does a mass spectrometer give you about a sample?
it tells us the relative isotopic mass of each substance in the sample along with the abundance of each
what does isoelectronic mean ?
substances are isoelectronic with one another if they have the same electron configuration
what does isoelectronic mean ?
substances are isoelectronic with one another if they have the same electron configuration
What is the unit of ionisation?
Kk mol-1
