Periodicity Flashcards
What is the definition of periodicity
Periodicity – how properties change across a period.
What is the definition of alkaline earth metals
Alkaline earth metals – Group 2 as their oxides and hydroxides are alkaline.
What is the definition of first ionisation
First ionisation energy – the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous +1 ions.
What is the definition of period
Period – A horizontal row in the periodic table.
What is the definition of group
Group – A vertical column in the periodic table.
What happens to ionisation energy across a period?
Generally increases.
Why does the trend in periodicity across a period occur?
Increased nuclear charge. Same shielding. Radius decreases.Outer electron held with greater nuclear charge so more energy needed to remove it.
Which groups don’t fit the trend in ionisation energy?
Group 3 and Group 6
What is the difference in ionisation energy for group 3 and 6?
Lower than expected.
Why does Aluminium have a difference in ionisation energy?
Aluminium 3p1 electron is further from the nucleus and shielding from 3s2 so less energy needed to remove it.
Why does Sulfur have a difference in ionisation energy?
Sulphur 3p4 electrons are paired in a p orbital. The additional repulsion lowers energy required to remove one of them.
What happens to the melting point across period 3 of the metallic elements?
Increases
Why does the trend across period 3 happen?
Number of outer electrons increase. More delocalised electrons. Greater attraction between the positive ions and delocalised electrons.Size of ions decreases. Greater attraction between smaller ions and delocalised electrons.
What happens to the boiling point of silicon?
Very high
What type of bonding does silicon have?
Giant covalent structure.
Why does silicon have this boiling point?
Lots of energy needed to break the strong covalent bonds.
What happens to the boiling point of phosphorous, sulphur and chlorine?
Low
What type of bonding does phosphorous, sulphur and chlorine have?
Simple covalent molecules.
Why do phosphorous, sulphur and chlorine have low boiling and melting points?
Little energy needed to overcome the van der Waals’ forces.
What is the trend in boiling and melting points across phosphorous, sulphur and chlorine and why?
P4, S8, Cl2 so more IM forces in S8 than P4.
Which period 3 element has the lowest melting and boiling point?
Lowest
What type of bonding does Argon have?
Atoms so very weak van der Waals’
What happens to the atomic radius across period 3 and why?
Decreases. Increasing nuclear charge. Same shielding. Outer electrons drawn in closer.
