Periodicity Flashcards
What groups are in which blocks on the periodic table?
Groups 1-2: s block
Transition metals : d block
Groups 3-0/8 : p block
Explain the trend in atomic radius going across the period (3)
As you go across the period, the atomic radius decreases.
This is because the nuclear charge increases and the energy levels stay the same. The increase in nuclear charge pulls the outer electrons closer to it.
Trend in 1st IE going across period (3)
The general trend is for an increase in the first ionisation energy as you go across the period due to the increasing nuclear charge.
What are the two exceptions in the trend of ionisation energies in the 3rd period
- Aluminium
- Sulfur
Why does aluminium not fit the trend in 1st IE?
The electron being removed from the group 3 element aluminium is in the P orbital while the one loss from the group 2 element magnesium is lost from an S orbital. The 3P orbital has a higher energy than the 3S orbital and is on average to be found further away from the nucleus. This makes it easier to lose.
Why does sulphur not fit the trend in first ionisation energies?
group 6 sulfur is the first occasion in the period that there is a pair of electrons in the same period orbital. The resulting extra electron electron repulsions makes it easier to lose electron from p4 than p3. So :
The electron is removed from paired P orbital which is easier to remove due to repulsion between electrons.
Which direction does ionisation energy graph shift when another electron is removed (eg 1st IE -> 2nd IE)
RIGHT
NB, graph is higher because 2nd IE are much greater because you are removing an electron from an already positive ion.
Trend in electronegativity across a period( 3)
Electronegativity is the ability to attract a shared power of electrons in a covalent
This increases across the period because :
- The number of protons in the nucleus increases
- The atomic radius decreases
What element in period three has the highest melting point and why?
Silicone, has giant covalent structure
