Answer:
frequency it the measure of the wave length. The measure of the peaks and troughs is how you measure the frequency. the distance between these is the wave length.
They have a different amount of neutrons.
The balanced equation would be 
<h3>Electrochemical equations</h3>
Zn reacts with Cu solution according to the following equation:

In the reaction,
is reduced according to the following: 
While Zn is oxidized according to the following: 
Thus, giving the overall equation of; 
More oxidation-reduction equations can be found here: brainly.com/question/13699873
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Explanation:
1) Thermal and Electric conductivity
2) Metallic strength