Term 1 Chemistry: Atomic Structure and Properties

• Term 1 Chemistry revision covers properties and structure of atoms, atomic spectroscopy, and mass spectrometry.

Weeks 1-3: Properties and Structure of Atoms

• Dalton's atomic model describes atoms as indivisible spheres.
• Thomson's atomic model is the "plum pudding" model with electrons in a positive sphere.
• Rutherford's atomic model describes a small, dense nucleus with orbiting electrons.
• Bohr's atomic model states electrons exist in fixed energy levels (shells).
• Chadwick discovered the neutron.
• Protons have a positive charge and are found in the nucleus.
• Neutrons have a neutral charge and are found in the nucleus.
• Electrons have a negative charge and orbit in energy levels.
• Electrons are arranged in energy levels (shells), for example, Sodium (Na) is 2,8,1.
• Isotopes are atoms with the same number of protons but different numbers of neutrons; for example, Carbon-12 and Carbon-14.
• Relative Atomic Mass (Ar) is the weighted average of isotopes.
• Relative Molecular/Formula Mass (Mr) is the sum of atomic masses in a compound.
• A Monatomic Ion is a single atom with a charge (e.g., Na⁺, Cl⁻).
• A Polyatomic Ion is a group of atoms with a charge (e.g., SO₄²⁻).
• Ionic Compounds are determined by balancing ion charges (e.g., NaCl, CaCl₂).
• Molecular Formulae show the number of each atom in a molecule (e.g., H₂O, CO₂, C₆H₁₂O₆).
• Percentage composition is calculated using the formula: % element = (mass of element ÷ total mass) × 100.
• A Mole (n) is 6.022 × 10²³ particles (Avogadro’s number).
• Moles are calculated using the formulas: ( n = \frac{m}{M} ) (where m = mass, M = molar mass) and ( n = \frac{N}{N_A} ) (where N = number of particles, N_A = Avogadro’s number).
• The periodic table arranges elements by increasing atomic number.
• Atomic radius decreases across a period and increases down a group.
• Electronegativity increases across a period and decreases down a group.
• Ionisation energy increases across a period and decreases down a group.

Weeks 4-5: Atomic Spectroscopy & Mass Spectrometry

• Different metal ions emit characteristic colours when heated in flame tests.
• Sodium emits yellow, copper emits green, and potassium emits purple.
• Atomic Absorption Spectroscopy (AAS) identifies elements by measuring absorbed light wavelengths.
• AAS is used in metal analysis, such as detecting lead in water.
• Mass Spectrometry separates ions based on mass and charge.
• Mass spectrometry determines isotopic composition and relative atomic mass.

Assessment Task

• Task 1 includes a topic test on atomic structure, chemical formula, and the mole concept.