Which of the following statements is true about the periodic table? the atomic radius increases moving down a column. the atomic radius decreases moving down a column. the chemical reactivity of metals increases moving from left to right. the chemical reactivity of nonmetals decreases moving from left to right.

option (a) is the correct answer.

Explanation:

In a periodic table, when we move from top to bottom in a periodic table then there will be increase in number of shells because of addition of more number of electrons.

As a result, there will be increase in atomic radius of the atom.

Metals are the elements which have excess of electrons but on moving from left to right in a periodic table reactivity of metals decreases as there valence shells does not contain extra electrons to donate.

On the other hand reactivity of non-metals increases on moving from left to right.

Hence, we can conclude that the statement atomic radius increases moving down a column, is true about the periodic table.

yes it is balanced

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.