Periodicity Flashcards
What is the definition if periodicity?
-The study of trends shown by the elements which repeat themselves in each period of the periodic table
Atomic Radius ………… down the group
Increases
Why does atomic radius increase down the group?
-There is an extra energy level every time and so shielding increases
-Resulting in weaker ESFA between electrons and nucleus
Atomic radius ………… across the period
Decreases
Why does atomic radius decrease across the period?
-Nuclear charge increases
-Shielding stays the same
-Stronger ESFA between nucleus and electrons
Why are does melting point increase from Na->Mg->Al
-Ionic radius decreases and charge increases
-Cations become more charge dense
-Increased no. Of delocalised electrons in the sea
-stronger ESFA between cations and delocalised electrons which require more energy to overcome
What is the trend in conductivity from Na->Mg->Al?
Conductivity increases
-No. of delocalised electrons in the sea increases
Why is the melting point of silicon the highest in period 3?
-Many strong covalent bonds between Silicon atoms require lots of energy to break
-Giant covalent structure
Phosphorus, Sulphur, Chlorine and Argon all have low melting points because…
-They have weak van de waals forces of attraction between molecules which require little energy to overcome
How many atoms are there in a sulphur molecule?
8 sulphur atoms
How many atoms are there in a Phosphorus molecules?
-4 Phosphorus atoms
How many chlorine atoms are in a chlorine molecule?
2
How many atoms are there in an Argon molecule
(Trick question)
Only one atom, argon exists as one atom
Why is the order of boiling points:
S > P > Cl > Ar
The bigger the molecule the stronger the vdws forces of attraction between molecules which require more energy to overcome
