A Level Chemistry Edexcel

This subject is broken down into 101 topics in 19 modules:

  1. Atomic Structure and the Periodic Table 5 topics
  2. Bonding and Structure 7 topics
  3. Redox I 4 topics
  4. Inorganic Chemistry and the Periodic Table 5 topics
  5. Formulae, Equations and Amounts of Substances 8 topics
  6. Organic Chemistry I 13 topics
  7. Modern Analytical Techniques I 2 topics
  8. Energetics I 4 topics
  9. Kinetics I 3 topics
  10. Equilibrium I 2 topics
  11. Equilibrium II 3 topics
  12. Acid-Base Equilibria 5 topics
  13. Energetics II 4 topics
  14. Redox II 5 topics
  15. Transition Metals 5 topics
  16. Kinetics II 7 topics
  17. Organic Chemistry II 4 topics
  18. Organic Chemistry III 11 topics
  19. Modern Analytical Techniques II 4 topics
Study this subject in the Adapt App →
  • 19
    modules
  • 101
    topics
  • 33,774
    words of revision content
  • 4+
    hours of audio lessons

This page was last modified on 28 September 2024.

A preview of A Level Chemistry Edexcel in the Adapt app

Adapt is a revision planning app with full content coverage and unlimited past paper questions for 1,200+ GCSE and A Level subjects.

Study this subject in the Adapt app →

Chemistry

Atomic Structure and the Periodic Table

Structure of Atoms

🤓 Study

📖 Quiz

Play audio lesson

Structure of Atoms

  • Atoms are the smallest unit of a chemical element, consisting of a central positively-charged nucleus surrounded by negatively-charged electrons.
  • The nucleus, at the centre of the atom, contains protons and neutrons.
  • Protons possess a positive charge while neutrons carry no charge. Together, these are known as nucleons.
  • Surrounding the nucleus are electrons which carry a negative charge. They exist in different energy levels or shells positioned around the nucleus.
  • The atomic number, also known as the proton number, represents the number of protons in the nucleus of an atom. This gives each atom its unique identity as a particular element.
  • The mass number, on the other hand, is the total number of protons and neutrons in an atom's nucleus.
  • Isotopes are atoms of the same element (same atomic number) but with differing numbers of neutrons (different mass numbers). As such, they possess the same chemical properties but may exhibit different physical properties.
  • The 'relative atomic mass' of an element takes into consideration the average mass of its isotopes relative to the mass of a carbon-12 atom.
  • Electrons occupy energy levels, also called electron shells, orbitals or quantum shells. The lower energy levels closest to the nucleus fill first.
  • Electron configuration explains how the electrons are distributed in these energy levels/orbitals. The first energy level can hold a maximum of two electrons, the second can hold up to eight electrons, and the third can hold eight as well.
  • The Periodic Table organises elements based on their atomic numbers. Going across a period from left to right, each element has one more proton and is less metallic than its predecessor.

Course material for Chemistry, module Atomic Structure and the Periodic Table, topic Structure of Atoms

Chemistry

Equilibrium I

Dynamic Equilibrium

🤓 Study

📖 Quiz

Play audio lesson

Dynamic Equilibrium

  • Dynamic equilibrium refers to a state in a closed system where the rate of forward and backward reactions is equal. Hence, the concentrations of reactants and products remain constant over time.
  • The principle of a dynamic equilibrium is applicable only to reversible reactions that occur in a closed system.
  • In a dynamic equilibrium, the concentrations of the reactants and products do not change over time. This, however, does not mean their amounts are equal.
  • The concept of dynamic equilibrium is explained by the collision theory - particles need to collide with each other for a reaction to happen. In a closed system, the number of collisions resulting in the forward reaction becomes equal to the ones resulting in the reverse reaction.
  • Le Chatelier's Principle is critical to understanding dynamic equilibrium. It states that if a system in equilibrium is subjected to a change, the system adjusts itself to offset that change, i.e., it tries to restore equilibrium.
  • Changes that can disturb a dynamic equilibrium include changes in concentration, temperature or pressure. The system will respond by favouring the direction that counteracts the change.
  • An increase in the concentration of reactants will cause the system to favour the forward reaction to consume the excess reactants and restore equilibrium. Similarly, increasing the concentration of products will favour the reverse reaction.
  • If a reaction is exothermic in the forward direction (releases heat), then increasing the temperature will cause the system to favour the reverse, endothermic reaction (which absorbs heat). The opposite is true if the forward reaction is endothermic.
  • For reactions involving gases, an increase in pressure favours the direction with fewer gas molecules, while a decrease in pressure favours the direction with more gas molecules.
  • Catalysis does not affect the position of the equilibrium, it only speeds up the rate at which equilibrium is reached.
  • The expression for the equilibrium constant (Kc or Kp) depends on the stoicheiometry of the reaction, and gives a quantitative measure of the position of equilibrium.
  • Chemical equilibrium can be quantitative, which is represented by the equilibrium constant, or qualitative, where only the direction of change is considered.
  • The constant for equilibrium, K, is given by the concentrations of the products divided by the concentrations of the reactants, each raised to the power of their stoichiometric coefficients. The concentration of solids and liquids is typically not considered in equilibrium constant expressions.

Course material for Chemistry, module Equilibrium I, topic Dynamic Equilibrium

Can I trust Adapt’s expertise?

Adapt is already used by over 600,000 students and trusted by over 3,000 schools. Our exam-specific content and assessments are meticulously crafted by expert teachers and examiners. To date, 4,894 students have studied for their A Level Chemistry Edexcel exams on the Adapt App.

Find out more about the Adapt app →

Planner

An always up-to-date revision timetable.

A personalised, flexible revision timetable that stays up-to-date automatically.

Content

All the exam resources, in one place.

Over 20,000 topics broken down into manageable lessons with teacher-written, exam-specific lessons.

Assessment

Past-paper questions, with instant feedback.

Unlimited past paper questions with instant examiner feedback on how to improve.

Progress

Track progress, together.

Progress tracking to stay motivated, with real-time updates to the Parent Portal.

Download the app today to start revising for free.