Group 4a (or 14) elements have electrons in their valence shell. a. 2 b. 3 c. 4 d. 5

Option (C) is the correct answer.

Explanation:

Elements of group 4A include carbon, silicon, germanium, tin and lead.

Also, it is known that valence shell is the shell which is present in the outermost side of an element.

Hence, the electrons present in this outermost shell are known as valence electrons.

For example, atomic number of carbon is 6 and its electronic configuration is .

This means that there are 4 electrons present in the outermost shell.

Thus, we can conclude that group 4A (or 14) elements have 4 electrons in their valence shell.

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.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.