Periodicity Flashcards
What is the least electronegative element?
Francium (0.7)
What is electronegativity?
A measure of the ability of an atom in a covalent bond to attract the electron bond pair
Why does electronegativity increase across a period?
Nuclear charge increased while radius decreases
Why does electronegativity decrease down any group?
As each element has an extra shell of electrons and a greater radius
Thus, less attraction for outer shell electrons
What is ionisation energy?
The energy needed to remove one mole of electrons from one mole of atoms or molecules in gaseous phase
How reactive is an element with the low IE?
Very reactive as it is easier to remove an electron
Generally ionisation energy increases across a period- why?
Nuclear charge increases with each added proton, while with little extra shielding.
Atomic radius decreases so more energy is needed to remove each electron
What are the anomalies of ionisation energy trends?
Group 2 to group 3 decreases as there is shielding by full s subshell
Be/B Mg/Al
N to O decrease as N has a half filled p subshell whereas O has slight e- pair repulsion = O’s electrons are lost more easily
Why does Aluminium have a higher melting point than other metals?
It has 3 delocalised electrons, therefore stronger attractions and smaller atomic cores
Describe the solubility of group 1 compounds
All are soluble
Is Mg(OH)2 soluble or insoluble?
Insoluble
How soluble is MgSO4?
Soluble
Are group 2 carbonates soluble?
No, all insoluble.
Is BaSO4 soluble?
No, insoluble
Give 2 balanced equations to show the amphoteric nature of Al2O3
With an acid
Al2O3 + 3H2SO4 -> 2Al2(SO4)3 + 3H2O
With a base
Al2O3 + 3H2O + 2NaOH -> 2NaAl(OH)4
Is Al2O3 soluble or insoluble?
Insoluble so doesn’t affect pH of water
What is the formula for Berylliumhydroxide?
Be(OH)2
What is the bonding in Be(OH)2 and why?
Ionic
High electronegativity
High charge density in Be2+ ion high polarises the anion- so has a covalent character in salts
Give two equations to show the amphoteric nature of Be(OH)2
With acid-
Be(OH)2 + 2HCl -> BeCl2 +2H2O
With base-
Be(OH)2 + NaOH -> Na2Be(OH)4
What elements show amphoteric behaviour?
Zn, Be, Al, Sn and Pb
What type of chloride reacts with water?
Give an example (with balanced eqn)
Covalent chlorides
PCl5 + H2O -> HCl + H3PO4
How do PCl3 and PCl5’s reaction with water differ?
PCl3 produces HCl and H3PO3
PCl5 produces HCl and H3PO4
