What is the rule for finding out how many valence electrons elements in groups 13-18 have

What molecules will be best used to compare different species with the exact same sequence of amino acids? why would two species have the same protein even if the molecules in question is different? (hint: transcription to translation to protein).

Compare and contrast your sells take in oxygen, water, and food. what is one waste product that leaves your cells?

Climate like that in the sahara desert have the fastest rates of weathering