O Level Chemistry - write formulae, covalent and ionic

Master the periodic table basics: read group numbers and identify metals versus nonmetals. Understand symbols, proton count on top, atomic mass at bottom, and that elements exist alone.

Explains solids, liquids, and gases, including fixed shape and volume for solids, fixed volume for liquids, and container filling for gases; covers melting, boiling, sublimation, condensation, freezing, and heating curves.

Explore diffusion as a natural process where particles move from high to low concentration, illustrated by perfume and coffee aromas, and see how temperature and molecular mass influence diffusion rates.

Identify group zero and metal atoms, and write their simple formulas. Memorize diatomic and key molecular formulas like O2, H2, N2, CO2, H2O, NH3, H2O2, SO2, PCl3.

Learn how to determine ion charges from the periodic table, write ionic formulas, and name ionic compounds, including transition metals and radicals.

Learn a three-step method to determine ionic compound formulas. Cross the charges, find the simplest whole-number ratio, and write the ionic formula with examples like magnesium chloride and ammonium sulfate.

Learn to write balanced chemical equations by identifying reactants and products, writing their formulae, and balancing to equalize atom counts.

Master how to add state symbols to chemical equations, distinguishing solid, liquid, aqueous, gas, and steam, and apply them to balanced reactions with practice questions.

Identify ionic compounds that are aqueous or liquid, split them into constituent ions, and cancel spectator ions to obtain the ionic equation for reactions such as acid-base neutralisation and precipitation.

Identify elements as pure substances of one atom type and explore how the periodic table organizes them, then compare compounds formed by chemical bonds and mixtures by physical mixing.

Explore the structure of atoms, including protons, neutrons, electrons, and the nucleus, and explain how relative atomic mass and mass number arise from isotopes and abundances.

Explore how atoms are electronically neutral, while ions form from gaining or losing electrons. Learn to compute charge using protons minus electrons and identify isotopes and electronic species.

Learn to write the electronic configuration of atoms by filling electrons into shells, with a two-electron first shell and eight-electron subsequent shells, using examples like oxygen, calcium, chlorine, and hydrogen.

Explore how to draw dot-and-cross diagrams for atoms, representing nucleus and electron shells, and identify all electrons versus just the valence (outermost) electrons using examples like oxygen, calcium, chlorine, hydrogen.

Metals and nonmetals form ions to achieve stable electron configurations, creating ionic bonds with electrostatic attraction; these compounds have high melting points and conduct electricity when molten or in water.

Show how metals lose and non-metals gain electrons to form ionic compounds, drawing dot-and-cross diagrams and using electronic configurations to derive formulas for NaCl, MgCl2, CaO, and Al2O3.

Describe covalent bonding in simple molecules via sharing electrons, giving low melting and boiling points; these molecules do not conduct electricity and are insoluble in water.

Learn to draw dot-and-cross diagrams for simple covalent molecules by determining composition, calculating valence electrons, and sharing electrons to achieve octets or duets, with step-by-step examples.

Explore macromolecules and polymers, contrast simple molecules with giant covalent structures like diamond and graphite, and explain melting points, conductivity, and lubricating properties tied to covalent bonds and layered structures.

Explore metallic bonding as the electrostatic attraction between metal ions and delocalized electrons. Learn why metals have high melting points and conductivity, and how brass and steel alloys gain strength.