Higher Chemistry SQA

This subject is broken down into 45 topics in 7 modules:

  1. Chemical Changes and Structure 5 topics
  2. Nature’s Chemistry 9 topics
  3. Chemistry in Society 8 topics
  4. Researching Chemistry 3 topics
  5. Inorganic Chemistry 6 topics
  6. Physical Chemistry 3 topics
  7. Organic Chemistry and Instrumental Analysis 11 topics
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  • 45
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  • 17,202
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This page was last modified on 28 September 2024.

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Chemistry

Chemical Changes and Structure

Chemical Changes and Structures: Periodicity

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Chemical Changes and Structures: Periodicity

Chemical Changes and Structures: Periodicity

Understanding Periodicity

  • Periodicity refers to the repeating patterns seen in the chemical and physical properties of elements arranged in the periodic table.
  • Periodicity arises due to the repeating pattern of outer, or valence, electron configurations of elements.
  • Trends in the periodic table are often described as being 'across a period' (left to right) or 'down a group' (top to bottom).

Trends Across a Period

  • Moving across a period, atomic size decreases due to increased nuclear charge pulling electrons closer to the nucleus.
  • Ionisation energy (the energy required to remove an electron from an atom) generally increases across a period. This arises from decreasing atomic size and increasing nuclear charge.
  • Electronegativity (ability of an atom to attract a bonding pair of electrons) generally increases across a period due to increased nuclear charge and decrease in atomic size.

Trends Down a Group

  • Moving down a group, atomic size increases due to the addition of electron shells.
  • Ionisation energy decreases down a group due to the increased atomic size and shielding effect.
  • Electronegativity decreases down a group since the bonding pair of electrons is further from the nucleus and more shielded.
  • Down a group, there is generally an increase in reactivity for metals and a decrease in reactivity for nonmetals.

Specific Group Trends

  • Group 1 elements (alkali metals) are characterised by a single electron in their outermost energy level, making them highly reactive metals.
  • Group 17 elements (halogens) have seven electrons in their outer shell, making them highly reactive non-metals.
  • Group 18 elements (noble gases) have full outer electron shells, making them very stable and unreactive.

Interpretation of Periodic Trends in Reactivity and Bonding

  • The reactivity of elements and the types of bonding they form (ionic, covalent or metallic) can often be predicted through understanding periodic trends.
  • The repetitive trends observed in the periodic table are immensely useful in predicting the behaviour of undiscovered or rarely encountered elements.

Course material for Chemistry, module Chemical Changes and Structure, topic Chemical Changes and Structures: Periodicity

Chemistry

Researching Chemistry

General Practical Techniques

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General Practical Techniques

Basic Concepts in Quantitative Chemistry

  • Quantitative chemistry involves making precise measurements and observations, using these to calculate unknown quantities.
  • Moles: Understand the concept of moles and the molar mass, which is the mass of one mole of a given substance.
  • Avogadro's number: Remember the number of particles in one mole of a substance, noted as 6.02 x 10^23, which is also referred to as Avogadro's number.

Techniques in Quantitative Chemistry

  • Titration: Learn the technique of titration where you add a solution from a burette to a known volume of another solution in a conical flask until the reaction is complete.
  • Balancing equations: Develop the ability to balance chemical equations, which can be used to predict the outcomes of reactions and to calculate reactant and product masses.

Investigation Techniques in Chemistry Research

  • Spectrometry: It's an analytical technique key for identifying and studying chemicals. Possible types include mass, infrared and UV/visible spectrometry.
  • Chromatography: Understand how to separate mixtures and identify substances through chromatography, which uses the principles of solubility and intermolecular forces.
  • Nuclear Magnetic Resonance (NMR) Spectroscopy: An advanced technique used to obtain detailed information about the structure of molecules.

Evaluation and Communication in Practical Chemistry

  • Always evaluate the reliability, precision and accuracy of quantitative experimental methods by considering any possible sources of error.
  • Use appropriate terms and conventions to communicate chemical information and data effectively: this includes chemical symbols, equations, diagrams, graphs and tables.

Course material for Chemistry, module Researching Chemistry, topic General Practical Techniques

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