Periodicity Flashcards
In the 1800’s how did they order the elements of the periodic table?
According to atomic mass
How are elements ordered?
By proton number not mass number
What is ionisation?
The minimum amount of energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state
Is ionisation endothermic or exothermic?
Requires energy- they are always an endothermic process therefore they always have a positive value
Shielding?
The more electron shells between the positive nucleus and negative electron that is being removed, the less energy is required
There is a weaker attraction
Atomic size?
The bigger the atom the further away the outer electrons are from the nucleus.
The attractive force between nucleus and outer electrons reduces- easier to remove electrons
Nuclear charge?
The more protons there are in the nucleus- the bigger the attraction between nucleus and outer electrons
This means more energy is required to remove the electron
What happens to ionisation energy as you go down a group?
Ionisation energy decreases.
Atomic radius does what when you go down the group?
Increases
The outer electrons are further from the nucleus
The attractive force is weaker
The energy required to remove an electron decreases
Shielding does what as you go down a group?
Increases
More shells between the nucleus and the outer shell
Attractive force is weaker
Energy required to remove an electron decreases
What happens to ionisation energy as you go across a period?
Increases
What happens to the nuclear attraction as you go across a period?
There is an increasing number of protons in the nucleus
This increases the nuclear attraction
What happens to shielding as you go across a period?
Similar
Distance from nucleus marginally decreases
What happens to the levels of energy needed to remove an outer electron?
Across a period more energy is required to remove an outer electron
Ionisation energy increases
What is a decrease at aluminium evidence for?
Atoms having sub-shells
What is the outer most electron in aluminium like compared to the outer electron in magnesium?
The outer most electron in aluminium sits in a higher energy sub-shell slightly further from the nucleus than the outer electron in magnesium
Aluminium has 3p1
Magnesium has 3s2
What is a decrease at sulphur evidence for?
Electron repulsion in an orbital
What are phosphorous’ and sulphurs’ outer electrons like?
They both have outer electrons in the 3p orbital so the shielding is the same
What does removing an electron from sulphur involve taking?
Involves taking it from an orbital with 2 electrons in
Is more or less energy needed to remove an electron from an orbital with 2 in than one with 1 in?
Less energy as electrons repel eachother
What is successive ionisation?
The removal of more than 1 electron from the same atom
How many times is each carbon bonded in graphite?
3 times
The 4th electron is delocalised
Does graphite have a high or low melting point?
High- lots of strong covalent bonds
How do layers slide easily in graphite?
There are weak forces between the layers
How does graphite have a low density?
Layers are far apart in comparison to covalent bond lengths
Is graphite soluble or insoluble?
Insoluble- the covalent bonds are too strong to break
How many times is each carbon bonded in diamond?
4 times in a tetrahedral shape
Can diamond conduct heat?
Yes- the tightly packed, rigid arrangement allows heat to conduct well in diamond
What can diamond be cut to make?
Gemstones
High or low melting point in diamond?
Very high due to many strong covalent bonds
Also very hard
Does diamond conduct electricity?
No as it does not have any delocalised electrons
Is diamond soluble or insoluble?
Insoluble- the covalent bonds are too strong to break
What do metals have in terms of structure?
Giant metallic lattice structures
How are positive metal ions formed?
Metals donate electrons to form a sea of delocalised electrons
What attraction is there between positive metal ions and negative delocalised electron?
Electrostatic attraction
How does the melting point in metals become higher?
The more electrons an atom can donate t the delocalised system- the higher the melting point
Why does magnesium have a higher melting point than sodium?
Magnesium can donate 2 electrons (group 2) whereas sodium can only donate 1
Are metals good thermal conductors?
Yes as the delocalised electrons can transfer kinetic energy
Are metals good electrical conductors?
Yes- the delocalised electrons are mobile and can carry a current
Are metals good thermal conductors/
The delocalised electrons can transfer kinetic energy
Do metals have high or low melting points?
High- due to the strong electrostatic attractions
Are solid metals insoluble or soluble?
Insoluble as the metallic bond is too strong to break
What happens to melting points in period 3?
General increase in melting points as metal ions have an increasing positive charge
Increasing the number of delocalised electrons and smaller ionic radius
This means a stronger metallic bond
The same trend for period 2 as well
Why does silicon have the highest melting point in period 3?
Has a giant covalent structure
What type of bonds hold the silicon atoms together?
Many strong covalent bonds- a large amount of energy is needed to overcome these strong covalent bonds
Why does phosphorus have a lower melting point than silicon?
Has a weaker simple molecular structure
The melting point is determined by weaker induced dipole-dipole forces
Why does sulfur have a higher melting point than phosphorus?
Has a larger simple molecular structure
Has larger induced dipole-dipole forces and therefore a higher melting point
Why does chlorine have a lower melting point than phosphorus and sulfur?
Has a smaller simple molecular structure
Has smaller induced dipole-dipole forces- therefore a lower melting point
Why does argon have a lower melting point than the rest of the elements in period 3?
It only exists as individual atoms
Has smaller induced dipole-dipole forces and therefore a lower melting point
Giant covalent state at room temp and pressure?
Solid
Simple molecular state at room temp and pressure?
Liquid or gas
BUT iodine is a solid
Giant ionic and metallic at usual state at room temp and pressure?
Solid
Solid
