What determines an atom's reactivity? #1. how many protons the atom contains.
#2. How many energy levels the atom contains.
#3. whether the atom is a metal or a nonmetal
#4. how many valence electrons the atom contains.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.