pure sodium and chlorine are extremely dangerous, but when combined the result in substance that we use every day. How do you think the properties of sodium and chlorine change when they are combined to make sodium chloride?

Explanation:

chlorine has 7 valence electrons while sodium has 1. on their own, they are very reactive elements. a full valence electron shell has 8 electrons, so when elements combine and have 8 electrons in their outer shell, they are not reactive. when sodium and chlorine are combined to form sodium chloride (table salt), it is no longer dangerous. the number of valence electrons changes its reactivity and how it combines.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

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