AS-Level Chemistry :Paper 1 2024 latest update graded a+

AS-Level Chemistry :Paper 1 2024 latest update graded a+ Arranged in periods (rows) and groups (columns) by atomic (proton) number - CORRECT ANSWER-How is the periodic table arranged Have the same number of electrons shells, even if they are not all parts of the s or p sub-shells - CORRECT ANSWER-All elements within a period ... Have the same number of electrons in their outer shell, meaning that they all have similar properties - CORRECT ANSWER-All elements within a group ... Periodicity - CORRECT ANSWER-The trends in the physical and chemical properties of elements as you go across the periodic table. Atomic radius across period 3 - CORRECT ANSWER-Atomic radius across period 3 goes as follows: 1) As the number of protons increases the further down a period you go, the positive charge of the nucleus increases 2) And though the amount of electrons increases across a period, they are added to the outer energy level - So their isn't any extra shielding 3) This means that the electrons are pulled closer to the nucleus, causing the atomic radius to decrease 4) Therefore, that overall the atomic radius of an atom decreases across period 3 with the largest radius being the first element, Na, and the smallest being the last element, Ar Melting points across a period 3 - CORRECT ANSWER-The melting point across period 3 goes as follows: 1) At the start with sodium, magnesium and aluminium their melting points increase. This is because they are metals and have strong electrostatic forces to overcome - The bonds get stronger by the time you reach Al due to having and more positively charged nucleus, increased number of delocalised electrons and a decreasing radius 2) From Al to Silicon, the melting point increases further as Si is a macromolecular substance which has very strong covalent bonds that take a lot of energy to break 3) However, the melting point then drops due to phosphorus, sulfur, chlorine and argon all being molecular substances. The issue with being that kind of substance is that to break the bonds apart all you need to do is to overcome the weak Van der Waals forces - A very easy task 4) The difference in melting points between P, S, Cl and Ar is that some molecules are bigger than others which leads to slightly greater Van der Waals forces First ionisation energy across period 3 - CORRECT ANSWER-First ionisation energy across period 3 goes as follows: 1) As you mover across the period, the general trend is for the ionisation energy to increase - This is due to an increase in number of protons within an atom as you go across the period which leads to a stronger nuclear attraction 2) The electrons do not counter this increase in protons due to the electrons remaining in roughly the same energy level which means their is little shielding affect or extra distance to lessen the attraction from the nucleus - Though there is a dip between elements in Mg and Al, P and S 3) The issue between Mg and Al is that Al has a 3p outer orbital rather than the 3s on Mg. Because of this the outer most electron in Al is further away from the nucleus and has an extra layer of shielding in the form of a 3s 4) As for the drop from P to S, this is because, though the ionised electron come out of the same sub-shell for both P and S. However, in P case the electron is being removed from a single occupied shell whereas is is being removed from an orbital containing two in S. The repulsion between the two electrons means that the electrons are easier to remove from shared orbital Increases as you go down the group due to extra electron shells as you go down the group - CORRECT ANSWER-Atomic radius across group 2 First Ionisation Energy down Group 2 Alkali Metals - CORRECT ANSWER-First ionisation energy down Group 2 Alkali Metals goes as follows