CAIE AS Level Chemistry Past Paper PDF

ZNOTES.ORG UPDATED TO 2023-2025 SYLLABUS CAIE AS LEVEL CHEMISTRY SUMMARIZED NOTES ON THE THEORY SYLLABUS Prepared for Batsirai for personal use only. CAIE AS LEVEL CHEMISTRY 1. Atomic Structure 1.1. Subatomic Particle Relative Subatomic Particle Relative Mass/...

ZNOTES.ORG UPDATED TO 2023-2025 SYLLABUS CAIE AS LEVEL CHEMISTRY SUMMARIZED NOTES ON THE THEORY SYLLABUS Prepared for Batsirai for personal use only. CAIE AS LEVEL CHEMISTRY 1. Atomic Structure 1.1. Subatomic Particle Relative Subatomic Particle Relative Mass/ a.m.u Charge Protons (P) +1 1 Neutrons (n) 0 1 Electrons (e-) -1 1/1840 1.2. Protons, Neutrons and Electrons Protons: positively charged ∴ deflected to -ve pole Neutrons: no charge ∴ not deflected Mass concentrated within the centre, nucleus Electrons: negatively charged ∴ deflected to +ve pole An atom is electrically neutral; P+ = e- Atomic number or proton number (Z) = no. of protons e- lighter than P+ ∴ deflected at greater angle Atomic mass or nucleon no. (A) = no. of P + N 1.4. Electronic Configuration Electrons are arranged in energy levels called shells Each shell is described by a principle quantum no. (P.Q) As the P.Q. increases, the energy of the shell increases Inside the shell, there are subshells: s, p, d and f Orbital: region in space where there is a maximum probability of finding an electron Isoelectronic Ions: ions having the same no. of e-s Isotopes are atoms of the same element with the same proton number but different numbers of neutrons Isotopes have similar chemical properties since they have the same number of protons and electrons (so chemical interactions are similar) Each orbital can hold 2e-s in opposite directions Isotopes have different physical properties since they have different numbers of neutrons, causing When e-s are placed in a set of orbital of equal energy, them to have different masses and, therefore, they occupy them singly, and then pairing takes place different physical interactions. e-s placed in the opposite direction: both -ve charge & if placed in the same direction, they’d repel. In the 1.3. Behaviour of a Beam of Subatomic opposite direction, they create a spin to reduce repulsion Completely filled or half-filled (i.e. one e- in each orbital) Particles are more stable (reduced repulsion) WWW.ZNOTES.ORG Copyright © 2024 ZNotes Education & Foundation. All Rights Reserved. This document is authorised for personal use only by Batsirai at Peterhouse Boys on 01/12/24. CAIE AS LEVEL CHEMISTRY Examples of this Method are Shown Below: Energy difference between 4s & 3d very small ∴ an e- from 4s can be promoted to half-fill or full-fill 3d orbital to make the atom more stable When filling, fill 4s before 3d and when removing, also remove first from 4s 1.6. Orbitals s orbitals are spherical, with the nucleus at the centre p orbitals are dumbell-shaped In certain cases (e.g., period 3 elements), an electron would prefer the 4s orbital over 3d while filling up. For example, 2 electrons in Titanium would be filled into the 4s orbital before 2 electrons are filled in the 3d orbital. This is because the 4s orbital is a more stable (lower) energy level than the 3d orbital. However, while losing electrons, the electrons from the 4s orbital would be lost first, and then those from the 3d orbital would be lost. This is because the 4s orbital is outer than the 3d orbital. A free radical is a species with one or more unpaired 1.5. Subshells electrons. s p d f Note: ions and free radicals are different. Orbitals 1 3 5 7 Max e-s 2 6 10 14 1.7. Ionisation Energies (I.E) Aufbau’s Principle: method of showing how atomic 1st I.E: the energy needed to remove 1 mole of e-s from orbitals are filled in a definite order to give the lowest 1 mole of a gaseous atom to form 1 mole of unipositive energy arrangement possible ions Each Successive I.E is higher than the previous one because as e-s are removed, protons > e-s ∴ the attraction between protons and remaining electrons increases Successive I.Es have a large jump in their value when e-s removed from the lower energy shell Deduce group no. by checking when 1st big jump occurs WWW.ZNOTES.ORG Copyright © 2024 ZNotes Education & Foundation. All Rights Reserved. This document is authorised for personal use only by Batsirai at Peterhouse Boys on 01/12/24. CAIE AS LEVEL CHEMISTRY Down a group (decreases): New shells added Attraction of nucleus to valence e-s decreases Shielding effect increases Across a period (increases): Shell number remains the same Proton number increases Effective nuclear charge increases Atomic radius decreases 1.10. Trend in 1st I.E across 3rd Period 1.8. Factors Affecting Ionisation Energy Nuclear Charge +ve charge due to protons in the nucleus Greater nuclear charge means greater ionization energy Shielding Effect Inner shells of e-s repel outermost e-s, thus shielding them from the +ve nucleus. The more e- shells, the greater is the shielding effect Greater effect lower I.E because lesser attractive force between nucleus & outer e-s I.E of Al lower than Mg: e- removed in Al is from higher Atomic Radius energy 3p orbital which is further away from nucleus Distance from the centre of the nucleus to the than 3s e- being removed from Mg. Nuclear attraction is outermost orbit less for 3p than 3s ∴ I.E of Al is lower than Mg As the number of electron shells increases, the atomic radius increases I.E of S lower than P: e- being removed in P is in a half As the number of electrons in the outermost shell filled, more stable 3p orbital whereas in S, the pairing of increases, the atomic radius decreases as the electrons in 3p results in increased repulsion ∴ less electrostatic attraction between the nucleus and energy need to remove an e- outer electrons increases Greater radius lower I.E; a distance of outermost e- to 1.11. Ionic Radius the nucleus is large ∴ less energy needed to remove e- Ionic Radius: describes the size of an ion Stable Configuration High I.E needed to remove e-s from completely or half-filled orbitals 1.9. General 1st Ionisation Energy Trends WWW.ZNOTES.ORG Copyright © 2024 ZNotes Education & Foundation. All Rights Reserved. This document is authorised for personal use only by Batsirai at Peterhouse Boys on 01/12/24. CAIE AS LEVEL CHEMISTRY Positive Ion: smaller radius than original neutral atom because shell no. decreases, the screening effect decreases, but the attraction of the nucleus increases. Negative Ion: larger ionic radius than neutral atom because e-s added while nuclear charge remains same Groups 1 to 3 5 to 7 Ion Positive Negative No. of shells n−1 n Across the period: Proton no. and effective nuclear charge increases Ionic radius decreases Negative ions are always larger than positive ions in the same period as they have one more shell Ionic radius increases down the group since the number of electron shells increases. As the negative charge on anion increases, the ionic radius increases since the number of electrons gained increases such that the number of electrons exceeds the number of protons. As the positive charge on the cation increases, the number of electrons lost increases, so the electrostatic attraction between the nucleus and outer electrons increases. WWW.ZNOTES.ORG Copyright © 2024 ZNotes Education & Foundation. All Rights Reserved. This document is authorised for personal use only by Batsirai at Peterhouse Boys on 01/12/24. CAIE AS Level Chemistry © ZNotes Education Ltd. & ZNotes Foundation 2024. All rights reserved. This version was created by Batsirai on Sun Dec 01 2024 for strictly personal use only. These notes have been created by Muneeb Rehman for the 2022-2024 syllabus. The document contains images and excerpts of text from educational resources available on the internet and printed books. If you are the owner of such media, test or visual, utilized in this document and do not accept its usage then we urge you to contact us and we would immediately replace said media. No part of this document may be copied or re-uploaded to another website. Under no conditions may this document be distributed under the name of false author(s) or sold for financial gain. "ZNotes" and the ZNotes logo are trademarks of ZNotes Education Limited (registration UK00003478331).