Periodicity Flashcards
Everything you need to get an A* in AQA Chemistry A level, closely following the AQA specification and textbook
What is a group on the periodic table?
A vertical column of elements that have similar properties
What is a period on the periodic table?
Horizontal rows of elements in the periodic table
Where is the s block on the periodic table?
The two rows on the far left is the s block
Why is the s block called the s block?
All elements in the s block have their highest energy electron on s obritals
What is the trend in melting points in period 3?
The melting points increases between Na and Al, then Si has the highest melting point. The melting point decreases between Si and P significantly, then from P to Ar, the melting points are low
Why does the boiling point increases between Na and Al?
As you go from Na to Al, the charge on the ion increases, so more electrons are delocalised, increasing the strength of the metallic bonds
Why does Silicon have the highest melting point?
Silicon has a giant covalent structure, so it has a lot of electrons, leading to extremely strong van der Waals forces.
Why do element P to Ar have lower melting points?
They are all simple covalent molecules, with not many electrons, so they have weaker van der Waals forces compared to Si
What is the trend in atomic radius across period 3?
Atomic radius decreases across period 3
Why does the atomic radius decreases across period 3?
Across period 3, the shielding stays relatively the same, but the number of protons increases, so the outer electrons are more strongly attracted towards the nucleus
Define the first ionisation energy
Energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
What is the trend in first ionisation energy across Period 3?
First ionisation energy increases across period 3
Why does the first ionisation energy increase across period 3?
Across period 3, the number of protons increases, but shielding stays relatively constant, so the outer electrons are more strongly attracted to the nucleus, making it increasingly difficult to remove an electron
What are the two anomalies in period 3 in terms of the trend in first ionisation energy?
Aluminium and Sulfur have a slight drop in first ionisation energy compared to the element before them
Why does aluminium have a lower first ionisation energy than Magnesium?
Magnesium loses a 3s2 electron, but Aluminium loses a 3p1 electron, which is in a higher energy level than the s electron in Mg, so less energy is required to remove it
Why does sulfur have a slightly lower first ionisation energy than phosphorus?
Phosphorus has no paired electrons in a p orbital, as each p electron is in a different orbital. Sulfur has two of its p electrons paired in a p orbital, so one of these is easier to remove than an unpaired electron due to their repulsion
