The two are potassium and rubidium. Why? Na is an alkali metal. As you go down the metals become more reactive.
Calcium has 20 protons. Why? The atomic # is 20 (the one at the top).
It has 20 neutrons. Why? The atomic mass (the number on the bottom) is ~40, ignoring electron mass. 40- 20 protons = 20 neutrons.
It has 20 electrons.
Why? The # of protons and electrons is the same. Ions aren't on the periodic table.
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Mechanisms of evolution correspond to violations of different Hardy-Weinberg assumptions. They are: mutation, non-random mating, gene flow, finite population size (genetic drift), and natural selection.
True, Methane is a greenhouse gas
Red Orange Yellow Green Blue Indigo Violet
<---Longest wave length shortest wave length--->
As you went down the colors of the rainbow the wave length got shorter or faster.
