Periodicity Flashcards
Why does the atomic radius decrease along a period?
There is an increased nuclear charge or the same number of electron shells. the outer electrons are pulled in closer to the nucleus as the increased charge produces a greater attraction.
Why does the atomic radius increase down a group?
As an electron shell is added each time. This increases the distance between the outer electrons and the nucleus reducing the power of attraction. more shells also increases electron shielding where the inner shells create a barrier that blocks the attractive force
Describe the ionisation energy along a period and why it does that
Along a period ionisation energy increase. The decreasing atomic radius and increasing nuclear charge means that the outer electrons are held more strongly and therefore more energy is required to remove the outer electron and ionise the atom.
Describe the ionisation energy down a group and why it does that
Ionisation energy decreases down the group as the nuclear attraction between the nucleus and outer electrons reduces and increasing amounts of shielding means less energy is required to remove the outer electron.
Why is there increasing melting points going from sodium to aluminium?
As there is an increase in the size of the positive charged ons as well as increasing number of electrons being released into sea of delocalised electrons forming a greater attractive electrostatic force.
Why does silicon have a very high melting point?
It is a macromolecular structure so it is made of very strong covalent bonds required lots of energy to break
Why do phosphorus, sulphur and chlorine have such low melting points?
They are all simple covalent molecules held with weak van der Waals forces and little energy is required to break these bonds.
Why does argon have such a low melting point?
It is a noble gas with a full outer shell of electrons making it very stable and it holds very weak van der Waals forces between molecules.
