8 - Periodicity Flashcards
What is periodicity?
Patterns in the properties of elements.
What trends can be seen in Groups?
Similar properties
Same number of valence electrons
Metals get more reactive down a group
Non-metals get less reactive down a group.
What are transition metals?
Fairly unreactive metals.
What trends can be seen in Periods?
Trends in physical and chemical behaviour.
Same number of energy levels/ electron shells.
How do the boiling points and melting points of Na, Mg, and Al change across Period 3?
They all have hight mp. and b.p as they all metallic bond, which is strong due to the strong attraction between cation and delocalised electrons.
Their mp. and b.p increases as the size of the ions increase, so there is more delocalised electrons and a greater charge therefore stronger metallic bonding.
Why does Si have a high mp. and b.p in Period 3?
It forms giant covalent molecules (macro molecular). The strong bonds mean more energy is needed to break the many bonds.
How do the boiling points and melting points of P, S, and Cl change across Period 3?
General decrease.
As the strongest IMF is van der Waal’s the larger the molecule (S8 > P4 > Cl2) the greater the electron density therefore the bigger the temporary dipole so the stronger the van der Waal’s forces.
Why does Ar have a low mp. and b.p in Period 3?
It is a monatomic atom, meaning it exists on its own therefore it has the weakest van der Waal’s force.
What is the trend of atomic radius across a period?
Decrease.
As the nuclear charge increases while the shielding stays similar there is a stronger electrostatic attraction between the nucleus and valance electrons therefore pulling the electrons closer to the nucleus.
What is the trend of atomic radius down a group?
Increase
The number of energy levels increases therefore there is more shielding between he nucleus and valence electrons so the electrostatic attraction decreases between the valence electrons and nucleus.
