pericodity melting/boiling point and oxides Flashcards
why do elements become more metallic down a group
Metals lose electrons
As you go down a group the outer electrons are further away from the nucleus
So it would be easier to lose the outer electrons
More like a metal
melting goes from.. to
boiling goes from.. to
solid to liquid
liquid to gas
what happens to melting point across a period
Melting points increases across a period from group 1 to 4.
Then a sharp decrease to group 5, 6 and 7.
This is due to the type of structure and bonding that occurs.
what happens to the melting point down a group
More shells
More shielding between nucleus and delocalised electrons
Forces of attraction weaker and less energy required to overcome
More electrons therefore stronger induced dipole-dipole forces
Requires more energy to break the intermolecular forces
explain why the melting point increases as the atomic number increases
More electrons
Induced dipole -dipole forces are stronger
Therefore more energy required to break the intermolecular forces
key notes about oxides across a period
Bonding with oxygen changes from ionic to covalent across a period.
When added to water solutions become more acidic across a period.
Structure changes from giant to simple across a period.
State symbol at room temperature changes from solid to gas across a
period.
Explain why SiO2 has a high melting point but CO2 has a low melting
point. Answers in terms of structure and bonding
SiO2 is giant and contains many strong covalent bonds which require a lot of energy to break.
CO2 is simple covalent and therefore only need to break the intermolecular forces/London forces between molecules which are weak and require a small amount of
energy to break
Explain why Ar and Ne do not react with oxygen
Ar and Ne are group 8/0/noble gases and therefore don’t form molecules because they already have full outer shells as atoms.
