đŸ§ȘChemistry

Applicable for A-Level, IB, DSE, AP-Level Exams

Atomic Structure    Stoichiometry    Bonding    Energetics    Kinetics    Equilibria    Redox    Group 2    Group 7    Alkanes    Alkenes and Alcohols    Organic Analysis    Thermodynamics    Kinetics 2    Equilibrium Constant Kp    Electrode Potentials & Cells    Acids, Bases & Buffer    Periodicity    Transition Metals    Inorganic Compounds in Acqeous Solutions    Optical Isomerism    Aldehydes & Ketones    Carboxylic Acids & Derivatives    Aromatic Chemistry    Amines    Polymers    Amino Acids, Proteins & DNA    Organic Synthesis    NMR    Chromatography   

Atomic Structure

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Electronic Structure

Electronic structure describes the placement and configuration of electrons around the nucleus in an atom. Shells are split in sub-shells which contain a finite number of orbitals. An atomic orbital is a region in space where there is a high probability of finding up to 2 electrons with opposite spins. Orbitals are classified into s, p, d and f. A subshell holding s-orbitals could only hold 1 s-orbital, whereas a subshell holding p-orbitals could hold 3 p-orbitals, hence holding a maximum of 3 x 2 = 6 electrons.


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Mass Spectrometry

Mass spectrometry is used to find the abundance and mass of each isotope and find the molecular mass of substances. There are 4 stages to this process: Ionisation, Acceleration, Flight Tube and Detection. Sample is first ionised either by electron impact or electrospray ionisation, then it is accelerated using an electric field to gain the same kinetic energy. Lighter ions travel faster and reach the negatively charged detector plate first than heavier ones.


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Atomic Models

There are different models of the atom that have been improved and changed over the years.

  • Dolton's atomic theory of matter described that all matter is made up of tiny marticles called atoms.
  • Later, Niel's Bohr's model of the atom describes that the mass of an atom contains protons and that electrons are arranged in definite energy levels.
  • Rutherford then improved on this model by saying that nearly all of the mass of an atom is concentrated at the positively charged nucleus and that the majority of an atom is empty space.

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