Ap biology exam 2020 Latest Update with Solutions

Ap biology exam 2020 Latest Update with Solutions how many elements are required for life - Answer -25 what elements make up 96% of living things? - Answer -C, H, O, N what elements make up the remaining 4% of living things? - Answer -P, S, Ca, K trace elements - Answer -required by an organism in only minute quantities what are examples of trace elements? - Answer -Fe: get it from things like spinach, meats, cereal I: get it from salt what are atoms? - Answer -smallest units of matter what are atoms composed of? - Answer -protons, neutrons, electrons what is atomic number? - Answer -number of protons what is atomic mass? - Answer -Number of protons and neutrons what are unstable atoms? - Answer -ions and isotopes describe ions - Answer --different # of electrons -atoms with a charge -more electrons and charge is negative -less electrons and charge is positive describe isotopes and give examples - Answer --different # of neutrons -often radioactive -used as diagnostic tracers -ex: barium & iodine why do atoms bond? - Answer -Atoms bond to attain a stable valance electron configuration (8 valence electrons) by bonding with other atoms. what is the octet rule? - Answer -Atoms tend to gain, lose or share electrons in order to have a full set of valance ent bonding - Answer -results from the sharing of electron pairs between two atoms what are the types of covalent bonds? - Answer -polar and nonpolar nonpolar covalent bond - Answer -A bond between 2 nonmetal atoms that have the same electronegativity and therefore have equal sharing of the bonding electron pair ex: O2 polar covalent bond - Answer -A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive. ex: H2O hydrogen bonding - Answer -weak bon