Below picture contains the given models.
Answer: Option-B is the correct model.
Explanation: Solid is a state of matter in which the particles are closely packed, has definite volume and shape. Like liquids they don't flow, either they occupy the volume of container as that occupied by both gases and liquids. The inter-molecular forces between solid particles are very strong as compared to liquids ans gases. So, the model B has a particles very closely packed to each other.
Answer:

Explanation:
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In this case, since the undergoing chemical reaction is:

We first need to identify the limiting reactant given the masses of nitrogen and hydrogen:

It means that only 0.647 moles of ammonia are yielded, so the resulting enthalpy change is:

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Answer:
In the quantum-mechanical model of an atom, electrons in the same atom that have the same principal quantum number (n) or principal energy level are said to occupy an electron shell of the atom. Orbitals define regions in space where you are likely to find electrons.