An Exothermic reaction releases energy into the surroundings and so the products have more potential energy then the reactants. The enthalpy change is a negative value. Whereas, an endothermic reaction involves the absorption of energy into the system and so the reactants have more potential energy than the products. The enthalpy change is a positive value. This is clearly represented in energy profile diagrams.
Selenium (Se) the most common isotope of this element. The nucleus consists of 34 protons (red) and 46 neutrons (blue).
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Protons and neutrons are in the center of the atom, making up the nucleus. The charge on the proton and electron are exactly the same size but opposite. Neutrons have no charge.
In 2009, the US Geological Survey estimated the Arctic may be home to 30% of the planet's natural gas reserves and 13% of oil.
