Answer:
There are 6.022x10^23 molecules
Elements in group 1-2, 13-18, the number of valence electrons is related to the group number. For example, in the first group, the alkali metals there is one valence electron, however in group 13, there are 3 valence electrons. Valence electrons are also known as the outershell electrons.
The answer is D. A compound
A) iron melting is the only example of physical change, because it's just a change of state (from solid to liquid).
The others, rusting, combustion, and decay are all chemical changes, because it will result in changing the chemical bonds between the atoms.
