Periodicity Flashcards
What is periodicity?
Patterns in properties across in a row which is repeated in each row.
As you go across period 3, what happens to the atomic radius and why?
The atomic radius decreases because all outer electrons are in the same shell and there is the same amount of electron shielding. The nucleus gets more protons, so is more positive, so there’s a stronger attraction between the nucleus and the outer shell electrons so the outer shell electrons are pulled closer to the nucleus, decreasing the atomic radius.
What is 1st ionisation energy?
The enthalpy change to remove one electron from each atom in one mole of gaseous atoms.
As you go across period 3, what happens to the 1st ionisation energy and why?
The 1st ionisation energy increases as there is more attraction between positive nucleus and outer shell electron (due to more protons in nucleus).
What are the 2 exceptions in the trend of 1st ionisation energy across period 3?
A dip as you go from group 2 –> group 3.
A dip as you go from group 5 –> group 6.
Why is there a dip from group 2 –> group 3 in the trend of 1st ionisation energy across period 3?
Because in group 3, the outer shell electron is lost from a p orbital and in group 2, it is lost from an s orbital. A p orbital has a higher energy level than s orbital, so is easier to lose electrons from.
Why is there a dip from group 5 –> group 6 in the trend of 1st ionisation energy across period 3?
Because there is an extra electron (which is paired) and electron repulsions makes it easier to lose from p4 rather than p3.
What is electronegativity?
The power of an atom to attract the 2 electrons in a covalent bond.
As you go across period 3, what happens to the electronegativity of the atom and why?
The electronegativity increases because there are more protons in the nucleus and a smaller atomic radius, therefore a stronger attraction between the nucleus and the 2 electrons in a covalent bond.
