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Answer: Protons
The atom in a sample of an element must contain nuclei with the same number of protons. If the protons change in number, then the element will modify as well.
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If an element contains 8 electrons, then there would be 6 electrons that will be placed in the 2nd valence shell. Each shell in an atom can only take up a fixed number of electrons. For the first shell, only two electrons can be found. For the second shell, it can hold up to 8 electrons. However, for this case only six electrons can be found since the others are found in the first shell.
Answer: = C
Explanation:
evaporating some of the water contained in the solution will increase the concentration of the resulting solution, because there will be concomitant increase in the number of moles of the solute left in the solution.
Answer:
(B) HNO3 + NaOH
Explanation:
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In this case, for the production of sodium nitrate a substance having the sodium as a cation should react with another substance having the nitrate anion. Moreover, neutralization reactions are carried out when bases react with acids, such is the case of nitric acid and sodium hydroxide:

Thus, the answer is (B) HNO3 + NaOH as the other options involve salts rather than acids or bases as starting reactants.
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