Answer: negative , from , to , exothermic
Explanation:
An endothermic reaction is a type of chemical reaction in which energy is absorbed from the surrounding. The temperature of the surrounding decreases.
An Exothermic reaction is a type of chemical reaction in which energy is released into the surrounding. The temperature of the surrounding increases.
Endothermic reactions are those in which heat is absorbed by the system from the surroundings and exothermic reactions are those in which heat is released by the system to the surroundings. 
for Endothermic reaction is positive and
As on dissolution of salt, the temperature of water increases, the heat has been released from system into surroundings and thus is negative.
Answer:
d) Nucleus of the element does not change during the react
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Answer:
Answers are bellow.
Explanation:
The element with electron configuration 1s22s22p63s1 belong I A group in the periodic table and it is sodium because it loses one electron.
We have periodic table in attachments.
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell, which it readily donates, creating a positively charged ion—the Na+ cation. Its only stable isotope is 23Na.
The free metal does not occur in nature, and must be prepared from compounds.
It is soft metal, reactive and with a low melting point.
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