AP Biology Ch. 2 Vocab

2026-2027

isotopes

different atomic forms of the same element just a different number of neutrons

radioactive isotopes

unstable because the nucleus decays spontaneously by giving off particles and energy, used in biological tracers but damages cellular molecules

valence electrons

the electrons in the outermost shell of an atom

electronegative

an atom’s tendency to attract shared electrons toward itself when part of a chemical bond

hydrophobic

water fearing

cation

positive transfer of electrons in an ionic bond

buffer

minimizes changes in hydrogen and hydroxide, usually a weak acid or a weak base

greenhouse effect

natural process where specific gases in Earth’s atmosphere trap heat from the sun, sunlight passes through the air and warms the ground, and the ground releases this energy as heat which gases (CO2 & water vapor) catch and send back down

evaporative cooling

completely breaks all hydrogen bonds of a single water molecule, gives water a high boiling point and the remaining liquid is cooled

colloid

mixture that contains a suspension

hydrophilic

water loving