<span>A </span>chemical formula<span> is a way of expressing information about the proportions of </span>atoms<span> that constitute a particular</span>chemical compound<span>, using a single line of </span>chemical element<span> symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and </span>plus<span> (+) and </span>minus<span> (−) signs. A chemical formula is not a </span>chemical name showing how the atoms are arranged.
Answer:
a pure substance consists only of one element or one compound
a mixture consists of two or more different substances, not chemically joined together.
examples:
pure substance : Hydrogen gas - Diamond - Gold metal.
mixture : water and oil - mixtures of sand and water - trail mix
Explanation:
There appears to be no table shown, but I can still answer. Aluminum has 3 valence electrons
<span>An exothermic reaction is one in which there is the production of heat whereas an endothermic reaction is one in which heat is absorbed. For the choices above, the answer would be letter B. Ice melting in water and an ice pack turning cold absorbs heat which is why it is an endothermic reaction. Exploding fireworks and gasoline burning gives off heat which is why it is an exothermic reaction.</span>
