2.1 Periodicity
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Where are the s orbitals on the periodic table?
First 2 groups
Where are the d orbitals in the periodic table?
The ‘middle block’
Where are the p orbitals in the periodic table?
Groups 3-8
Where are the f orbitals in the periodic table?
The lanthanides
What is the atomic radius trend across period 3?
• Decreases • Charge increases but shielding stays the same. • Greater attraction so pulls the outer electrons closer to the nucleus. • Therefore a smaller radius
What is the trend if first ionisation energy across period 3?
• Increases - Stronger nuclear attraction (smaller AR), so needs more energy to lose the outer electrons.
What are the exceptions to the 1st IE trend?
• Between gr2 & 3 - Between gr 5 & 6
Explain the gr 2 & 3 exception in terms of 1st IE
The outer electron moves from the 2p - 2s orbital, so more shielding from sub shell, and therefore IE decreases here.
Explain the gr 5 & 6 exception in terms of 1st IE
Electrons start pairing up in orbitals (Hunds rule), so this ‘pair’ repulsion decreases the IE here.
What is the trend in melting points across period 3?
• Na, Mg, Al are metallic so high MP, gets bigger going along these. • Si is macromolecular, so strong covalent bonds and higher MP than metals. • P, S, Cl are simple molecular, so weak VDWS. Lower MP than metals but get bigger as you go along these. • Ar is monatomic so has a very low MP.