Atomic structure
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- Created by: r98
- Created on: 08-04-16 20:25
What 3 fundamental particles make up an atom?
Protons, neutrons and electrons.
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What is the relative mass, relative charge and position of a proton?
Relative mass = 1. Relative charge = +1 (coulomb). Position = in the nucleus.
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What is the relative mass, relative charge and position of a neutron?
Relative mass = 1. Relative charge = 0 (coulomb). Position = in the nucleus.
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What is the relative mass, relative charge and position of an electron?
Relative mass = 1/1840 (nearly 0). Relative charge = -1 (coulomb). Position = around the nucleus.
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Where are the protons and neutrons situated and what force holds them together?
They're located in the centre of the atom and are together by a force called the stron nuclear force.
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What forces hold electrons and protons together?
Electrostatic forces.
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Where are electrons found?
The nucleus is surrounded by electrons. Electrons are found in a series of levels (orbits/shells) which get further and further away from the nucleus.
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What were Gilbert Lewis' ideas to do with noble gases and formation of ions?
The inertness of noble gases was related to them having full outer shells of electrons. Ions were formed by atoms losing or gaining electrons to attain full outer shells (become stable).
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Is the electron a particle, a wave or a cloud of charge?
Electrons have some properties of waves as well as those of particles. Early theories model the electron as minute solid particle, but later theories suggest that an electron is a smeared out cloud of charge.
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What's the equation for the number of electrons in a shell?
Number of electrons in a shell = 2n^(2), where 'n' is the number of the shell.
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What's the maximum number of electrons in the first, second, and third shell?
First shell = 2. Second shell = 8. Third shell = 18.
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What would be the shorthand electron configuration of carbon?
2,4.
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What is the atomic number & what other name is given to it?
It's the number of protons in the nucleus. It's also called the proton number.
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In an atom, what is equal to the proton number, Z?
The number of electrons in the atom.
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What determines the chemical properties of an element?
The number of electrons in the outer shell of an atom.
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What is the mass number, A?
The total number of protons and neutrons in the nucleus.
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What are isotopes?
Atoms with the same number of protons but different numbers of neutrons.
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Chemically, how do different isotopes of the same element react?
They react in exactly the same way.
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What do atoms of different isotopes of the same element vary in?
They vary in mass number, because of the different number of neutrons in their nuclei.
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What is the use of a mass spectrometer? What does it determine?
For the accurate determination of relative atomic masses. It determines the mass of separate atoms (or molecules).
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What has to be done to the mass spectrometer to ensure that the ions do not collide with air molecules? Why is this important?
The mass spectrometer is kept under a high vacuum, because if the ions collide with sir molecules, it might stop them from reaching the detector.
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In what state (of matter) does the sample being investigated have to be in? What must be done to the sample if it's not in this state?
In the gaseous state. If the sample is a solid it's vaporised first by heating.
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What is the sequence of events that happens to atoms (or molecules) when they're in the mass spectrometer?
Ionisation ---> acceleration ---> deflection ---> detection.
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How is an atom (or molecule) ionised in a mass spectrometer?
A beam of electrons, from an electron-gun, knocks out electrons from atoms or molecules, forming positive ions.
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How many electrons do the atoms or molecules lose during ionisation in a mass spectrometer?
Nearly all atoms or molecules lose one electron, forming ions with a 1+ charge. But about 5% lose two electrons, forming ions witha 2+ charge.
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In a mass spectrometer, what's the next stage after ionisation?
Acceleration- the positive ions are attracted towards negatively charged plates and are accelerated to a high speed. Some ions passed through slits in the plates, which forms them into a beam.
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What does the speed to which the positive ions are accelerated, in a mass spectrometer, depend on?
The speed they reach depends on their mass - the lighter the ions, the faster they go.
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In a mass spectrometer, what's the next stage after acceleration?
Deflection - The beam of ions then moves into a magnetic field at right angles to its direction of travel. The magnetic field deflects the beam of ions into an arc of a circle.
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What does the deflection of an ion depend on?
It depends on the ratio of its mass to charge (m/z), z is the charge on the ion (usually 1+).
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*** does the deflection of heavier ions compare to the deflection of lighter ions?
Heavier ions are deflected less than lighterones.
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How does the deflection of 2+ ions compare to that of 1+ ions?
2+ ions are deflected twice as much as 1+ ions with the same mass.
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What is another factor that deflection depends on?
The magnetic field strength - the stronger the field, the greater the deflection.
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In a mass spectrometer, what's the next stage after deflection?
Detection- the magnetic field is gradually increased so that ions of increasing mass enter the detector one after another.
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What happens when ions strike the detector?
Ions strike the detector, accept electrons, lose their charge and create a current which is proportional to the abundance of each ion.
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Why can different isotopes be detected separately in a mass spectrometer?
It detects individual ions, so different isotopes are detected separately because they have different masses.
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How can the behaviour of ion with a 2+ charge be described?
They behave like ions with half the mass of a singly charged ion.
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On a mass spectrum, why do the peaks of doubly charged ions have very small abundances?
Because double ionisation is rare.
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What is a molecular ion?
A molecule of the sample which has been ionised but which has not broken up during its flight throught the mass spectrometer.
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In a mass spectrum, what is the heaviest ion likely to be?
The molecular ion.
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Do electrons in different shells have the same amount of energy?
No, electrons in different shells have differing amounts of energy.
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What sub-levels are the main energy levels divided into? Do these sub-levels have the same amounts of energy?
s,p,d and f. They have slightly different energies..
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What is an atomic orbital?
The volume in space filled by an electron.
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Do different atokic orbitals have different energies?
Yes.
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What can be said about the shape of the atomic orbitals of each main level?
They have different shapes, which have slightly different energies.
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What orbitals does the first main energy level consist of?
A single s-orbital.
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What orbitals does the second main energy level consist of?
A single s-orbital and three p-orbitals of slightly higher energy.
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What orbitals does the third main energy level consist of?
A single s-orbital, three p-orbitals of slightly higher energy, and five d-orbitals of slightly higher energy still.
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What is the maximum number of electrons an atomic orbital can hold?
2 electrons.
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Do the atomic orbitals of the same sub-level have the same amounts of energy?
Yes.
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In neutral atoms, does the 4s sub-level have higher or lower energy than the 3d sub-level?
4s is of slightly lower energy than the 3d.
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What can be said about the 'spins' of two electrons in the same orbital?
Two electrons in the same orbital must have opposite spins.
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What are the rules for filling atomic orbitals?
Atomic orbitals of lower energy are filled first - so the lower main energy level is filled first, and within this level, sub-levels of lower energy are filled first. & Atomic orbitals of the same energy fill singly before pairing starts.
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What is the full electron arrangement of sodium, 11 electrons?
1s^(2) 2s^(2)2p^(6) 3s^(1).
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What is the full electron arrangement of calcium, 20 electrons?
1s^(2) 2s^(2)2p^(6) 3s^(2)3p^(6) 4s^(2) (4s orbital is filled before the 3d orbital because it's of lower energy).
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What is the full electron arrangement of vanadium, 23 electrons?
1s^(2) 2s^(2)2p^(6) 3s^(2)3p^(6)3d^(3) 4s^(2).
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What is the electron arrangement of calcium, 20 electrons, using an inert gas symbol as a shorthand?
[Ar]4^(2).
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What is the definition of ionisation energy, IE?
The energy required to remove a mole of electrons from a mole of atoms in the gaseous state.
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What is ionisation energy measured in (units)?
kJ/mol.
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Why is the second IE higher than the first IE?
The second electron needs more energy than the first because it's being removed from a 1+ ion.
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What is the equation for the first IE of sodium, Na?
Na(g) -----> Na+(g) + e-.
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Using the successive ionisation energies, how can you find the number of electrons in each main level of any element?
By looking at the jumps in successive ionisation energies.
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What is the general trend in ionisation energies across a period? What's an explanation for this?
Ionisation energies generally increase across a period because the nuclear charge is increasing and this makes it more difficult to remove an electron.
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Why does the first IE, from magnesium to aluminium, go down?
Because the outer electron in aluminium is in a 3p orbital which is of a slightly highdr energy than the 3s orbital. It therefore needs less energy to remove it.
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Why is there a small drop between phosphorus and sulfur, in their first ionisation energies?
In phosphorus, each of the three 3p orbitals contains just one electron, while in sulfur, one of the 3p orbitals contains two electrons. The repulsion between these paired electrons makes it easier to remove one of them.
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What do the decreases in first IE from magnesium to aluminium, and from phosphorus to sulfur, provide evidence for?
Both these cases, which go against the expected trend, are evidence that confirms the existence of s and p as sub-levels.
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What is the general trend of first ionisation energies down a group? What's an explanation for this?
There is a general decrease in first IE as you go down a group. This is because the outer electron is in a main level that gets further from the nucleus in each case.
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As you go down a group, nuclear charge increases, so why doesn't this make it more difficult to remove an electron?
The actual positive charge 'felt' by an electron in the outer shell is less than the full nuclear charge. This is because of the effect of the inner electrons shielding the nuclear charge.
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Other cards in this set
Card 2
Front
What is the relative mass, relative charge and position of a proton?
Back
Relative mass = 1. Relative charge = +1 (coulomb). Position = in the nucleus.
Card 3
Front
What is the relative mass, relative charge and position of a neutron?
Back
Card 4
Front
What is the relative mass, relative charge and position of an electron?
Back
Card 5
Front
Where are the protons and neutrons situated and what force holds them together?
Back
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