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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<span>Punctuated
Equilibrium/ Equilibria proposes that once species appear in the fossil record,
the population will be in the state of
little or absent morphologic change. This is called a state of stasis. The
theory further proposes that the population is confined to infrequent and
geographical rapid events when significant evolutionary change happens. The parent species will the split into two
distinct species. This process if called cladogenesis.</span>
All living organisms need to take substances from their environment to obtain energy, to grow and to stay healthy
