Atomic Structure Flashcards by Oluchi Ezekiel

What does an atom consist of?

An atom consists of a nucleus containing protons and neutrons surrounded by electrons

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What is the relative charge and mass of a proton ?

Relative mass is 1
Relative charge is +1

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What is the relative mass and charge of a neutron?

Relative mass is 1
Relative charge is 0

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What is the relative mass and charge of an electron ?

Relative mass is 1/1840
Relative charge -1

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What are isotopes?

Isotopes are atoms with the same number of protons and different number of neutrons

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Why do isotopes have similar chemical properties ?

Isotopes have similar chemical properties because they have the same electronic structure. They may have slightly varying physical properties because they have different masses.

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What can the mass spectrometer be used to determine ?

The mass spectrometer can be used to determine all the isotopes present in a sample of an element and to therefore identify elements

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Why does the mass spectrometer have to be under a vacuum?

It needs to be under a vacuum otherwise air particles would ionise and register in the detector

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What are the four steps of a mass spectrometer?

1.ionisation
2.acceleration
3.flight tube/ion drift
4.detection

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What are the two ways a sample can be ionised?

Electron impact
Electro spray ionisation

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Describe electron impact

A vaporised sample is injected at low pressure
An electron gun fires high energy electrons at the sample
This knocks out an outer electron
Forming positive ions with different charges e.g TI(g)->Ti+(g)+e-

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Describe electro spray ionisation

Sample is dissolved in a volatile polar solvent
Injected through a fine needle giving a fine mist or aerosol
The tip of needle has high voltage
At the tip of the needle the sample molecule M gains a proton H+ from the solvent forming MH+
M(g)+H+->MH+(g)
The solvent evaporates towards a negative plate

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What is electron impact used for?

Electron impact is used for elements and substances with low formula mass . Electron impact can cause larger organic molecules to fragment

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What is electro spray ionisation used for?

Electro spray ionisation is used preferably for larger organic molecules.The softer conditions of this technique mean fragmentation doesn’t occur

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Describe acceleration in a mass spectrometer

Positive ions are accelerated by an electric field to a constant kinetic energy

KE=1/2mv^2

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What does the velocity of each particle depend on ?

Given that all the particles have the same kinetic energy the velocity of each particle depends on its mass.lighter particles have a faster velocity and heavier particles have a slower velocity

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Describe the flight tube

Positive ions with smaller M/z values will have the same kinetic energy as those with larger M/z and will move faster. The heavier particles take longer to move through the drift area
The ions are distinguished by different flight times

t=d/v

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Describe detection

The ions reach the detector and generate a small current which is fed to a computer for analysis.The current is produced by electrons transferring from the detector to the positive ions .The size of the current is proportional to the abundance of the species

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What can the mass spectrometer measure for each isotope?

For each isotope the mass spectrometer can measure a M/z (mass /charge ratio) and an abundance

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How do you give the species for a peak in a mass spectrum?

If asked to give the species for a peak in a mass spectrum then give charge and mass number eg 24Mg+

Equation for R.A.M

R.A.M=

How are electrons arranged ?

Electrons are arranged around the nucleus in principal energy levels or principal quantum shells

What are principal quantum number used for?

Principal quantum numbers are used to number the energy levels or quantum shells

What does it mean if there’s a lower principal quantum number ?

Lower the principal quantum number the closer the shell is to the nucleus (first shell closest to nucleus is n=1)

What does a higher principal quantum mean in terms of distance?

Higher principal quantum number greater energy of the shell and the further away from the nucleus

How many electrons can each principal quantum level hold

N=1 up to 2 N=2 up to 8 N=3 up to 18 N=4 up to 32

What are subshells?

S p d f

What is the order of sub shells?

1s 2s 2p 3s 3p 4s 3d 4p 4d 4fp

How many electrons in s p d f

S=2 P=6 D=10 F=14

Which elements have an f shell?

Elements with more than 57 electrons also have an f shell

What do subshells contain ?

Subshells contain one or more atomic orbitals

How do orbitals exist ?

Orbitals exist at specific energy levels and electrons can only be found at specific levels not in between them

What can each atomic orbital be occupied with maximum?

Each atomic orbital can be occupied by a max of two electrons

Describe s orbital shape

Spherical Size of orbital increases with increasing shell number Can only accept 2 electrons with opposite spins

Describe p orbital

Dumbbell shape Each shell has three p orbitals except for the first one Contains a max of 8 electrons in 2 different sub levels The lobes of the p orbitals become larger and longer with increasing shell number

Describe ground state

Most stable electronic configuration of an atom which has the lowest amount of energy Achieved by filling the sub shells of energy with the lowest energy first

What electrons are filled first for transition metals?

The transition metals fill the 4s sub shell before the 3d subshells but lose electrons from the 4s first and not the 3d subshells(4s is the lowest in energy)

Define ionisation energy

For an atom to form a positive ion an electron must be given enough energy to be completely removed beyond the outer shell of the atom

What is the energy for one more of an atom in in terms of ionisation energy?

The energy for one atom is so small that the energies are quoted for one more of atoms in kilojoules mole^_1 at 298k (25degrees)

What is the first ionisation energy of an element?

The first ionisation energy of an element is the energy requires to remove one electron from one mole of gaseous atoms to form one mole of gaseous one plus ions

Ionisation energy equation

X(g )—>X+(g) + e-

What is the trend for the first ionisation energies for group 2 elements?

Ionisation energy decreases down the group As you go down group to the number of energy levels increases, therefore the outermost electrons are further from the nucleus Number of inner energy levels increases

Why is a 3P sublevel easiest to remove the 3S sub level?

3 P sub level is higher in energy than the 3S sublevel thought it’s easiest to remove the outermost electron from aluminium than it is for magnesium

Describe the second ionisation energy

Energy required to remove one electron from each ion in one mole of gaseous one plus ions to form one mole of gas is 2+ ion

What is the equation for the second ionisation energy?

X+(g)->X2+(g) + e-

Describe the third ionisation energy

Energy required to remove one electron from each ion in one mole of gaseous 2+ ions to form one mole of gassiest 3+ ion

What is the equation for the third ionisation energy?

X2+ (g) -> X3+ (g) + e-

How does the energy require to removing electron from the outermost energy level change for the successive ionisation energy?

The energy required to remove an electron from the atom energy level increases for successive ionisation energy because magnesium for example needs less amount of energy because the electron is being removed from neutral atom

What happens if an electron is being removed from a 2+ ion on the 2P is lower in energy than the 3S?

If an electron is being removed from a 2+ ion and the 2p is lowering energy than the 3S (electrons closer to nucleus so harder to remove as well as different in shielding needs more energy than others)