<span>Valence electrons are important because these are the only electrons involved with an atom's chemical reactivity.</span>
B, because water is changing its state from solid to liquid (it's fusion in portuguese, don't know in english), so while it's changing, water has 2 states at the same time.
The correct answer is industrial smog. This type of smog exists in coal power plants which creates smoke and sulfur dioxide which may mix with fog creating a thick blanket of haze. Sulfur dioxide is one primary component of an industrial smog.
Answer:
An allotrope is one way that atoms can be arranged in a solid. An isotope is one way that protons and neutrons can form the same atomic element.
