AQA A-LEVEL CHEMISTRY Periodicity Questions and Answers

AQA A-LEVEL CHEMISTRY Periodicity Questions and Answers BLOCKS What is the s, p, d and f block on the periodic table? S - 1,2 P - 3,4,5,6,7,8 D - Transition Metals F - Bottom. According to whatever the highest energy level is. ATOMIC RADIUS Why does the atomic radius decrease across the period? The increased number of protons pulls the electrons closer to it with minimal change in shielding to prevent that from ocurring. FIRST IONISATION ENERGY What is the general trend of the first ionisation energy across a period? Plus, what are the exceptions to do with Al and S General Trend - it increases due to the nuclear charge increasing. Al - Because Al's outer electron is in 3p whereas Mg's outer electron is in 3s, Al has a lower IE because the electron have more energy. S - Because sulfur's electrons are paired up, they repel eachother and hence are easy to remove. MELTING POINT What is the melting point like in a metal? For Na, Mg, Al- Metallic bonding : strong bonding - gets stronger the more electrons there are in the outer shell that are released to the sea of electrons. A smaller sized ion with a greater positive charge also makes the bonding stronger. Higher energy is needed to break bonds. MELTING POINT Why does silicon have a high melting point? It is macromolecular and hence has a lot of giant covalent bonds that must be broken. MELTING POINT Why do simple molecular structures have a low MP. weak van der waals between molecules, so little energy is needed to break them - low mp+ bp MELTING POINT Why does S₈ have a higher MP than P₄ S₈ has more electrons and hence stronger Van der Waals forces.