<span>If thermal energy (heat) must be added to a chemical reaction in order for the reaction to take place, the reaction is endothermic. </span>
Answer:
Explanation:
Ionic Compounds Are Balanced
Table salt is an example of an ionic compound. Sodium and chlorine ions come together to form sodium chloride, or NaCl. The sodium atom in this compound loses an electron to become Na+, while the chlorine atom gains an electron to become Cl-
Answer:
Explanation:The atomic number of sodium is 11. That is, the number of electrons in sodium is 11. Therefore, a sodium atom will have two electrons in the first shell, eight in the 2nd orbit, and an electron in the 3rd shell.
Answer:

Explanation:
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In this case, according to the given information it turns out possible for us to realize that one mole of the given compound, Mg(ClO₄)₂, has one mole of Mg, two moles of Cl and eight moles of O; thus, we proceed as follows:

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Answer:10,0000 years
Explanation:
If it takes 2000 years to weather 1cm of limestone
It will take 5*2000 years to weather 5cm of limestone. This gives us 10000 years.