<u>Answer:</u>
<em>A negative ∆H means that energy is given off from a reaction
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<u>Explanation:</u>

If the reaction has negative ∆H value then the reaction is exothermic

If the reaction has positive ∆H value then the reaction is endothermic
When Heat energy is given in the equation itself
If it is present on the left side it means that heat is absorbed and the reaction is Endothermic
If it is present on the right side it means heat is given off and the reaction is exothermic
Answer:
Atomic Oribal
Explanation:
There are four basic types of electron orbitals – s, p, d, and f. (Visual representations can be found in the tutorial above.) The s subshell is a spherical orbital which can contain up to two electrons. Each energy level has one s subshell.
Not sure if this is correct but i would choose the steel tray.
Answer:
A planet is believed to form when the mutual gravitational attraction of debris orbiting a star accumulates into a growing mass.
Explanation:
Planetary rings, then, consist of millions of separate small rock and ice particles, each maintaining their own orbit around the host planet.
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Magnesium appears as the cation Mg 2+ and Oxygen appears as the anion O 2- and when combined they create MgO, which is Magnesium Oxide.</span>