NCEA L1 ChemBio cheat sheet

Atomic number = number of protons; in a neutral atom it equals the number of electrons.

Mass number = protons + neutrons; isotopes of an element differ in neutron number only.

Electron configuration fills shells 2, 8, 8: e.g. Na (11 electrons) = 2,8,1.

Group number (main groups) gives outer-shell electrons; period number gives the number of occupied shells.

Ionic bonding: metal loses electrons to form a positive ion, non-metal gains electrons to form a negative ion; ions are held by electrostatic attraction.

Covalent bonding: atoms share electron pairs; a single bond shares one pair, a double bond shares two pairs.

Mole formula: n = m / M, where m is mass in grams and M is molar mass in g mol^-1.

Concentration formula: c = n / V, with V in litres; dilution obeys c1V1 = c2V2.

Reaction rate increases with higher temperature, higher concentration, greater surface area, or added catalyst.

Cell theory: all living things are made of cells, cells arise from pre-existing cells, and the cell is the basic unit of life.

Prokaryotic cells lack a membrane-bound nucleus and organelles; eukaryotic cells have a nucleus and membrane-bound organelles.

Mitochondria carry out aerobic respiration, releasing energy as ATP; chloroplasts carry out photosynthesis using chlorophyll.

Photosynthesis word equation: carbon dioxide + water (+ light energy) -> glucose + oxygen.

Aerobic respiration word equation: glucose + oxygen -> carbon dioxide + water + energy (ATP).

Enzymes are protein catalysts; each has an active site specific to its substrate, and activity is reduced by extremes of temperature or pH.

Diffusion moves particles from high to low concentration without energy input; osmosis is diffusion of water across a semi-permeable membrane.

DNA base pairing: adenine pairs with thymine, guanine pairs with cytosine; the sequence of bases encodes genetic information.

A food chain transfers energy between organisms; only about 10% of energy passes to the next trophic level, the rest is lost as heat.