The answer is C :
It controls the entry and exit of substances.
Answer:
1
Explanation:
outershell atoms of an element are also known as valency of that element
so the valency and number of elctron in the outershell of a sodium atom is +1.
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Answer:
The classification and illustrations are attached in the drawing.
Explanation:
It is possible to identify the pure substance observing the figure, since it is the only one that has 2 joined atoms (purple and blue) which forms a single compound.
On the other hand, the homogeneous mixture is identified by noting that its atoms are more united with respect to the heterogeneous mixture, highlighting that in homogenous mixtures the atoms, elements or substances are not visible to the naked eye and are in a single phase, instead in the heterogeneous mixture if they can be differentiated.
Answer: seas
Explanation:
The ancient astronomers thought the mares on the moon were seas.