All atoms of the same element must have the same number if protons, however the number of neutrons can vary, giving different isotopes of the element.
I'm not quite sure what you were looking for but I hope that this helps.
The 7.5 is a 100 times stronger than the 5.5 . The 100 comes from the increase in scale from 5.5 to 7.5 which is an increase of two so you multiply the strength of the weaker earthquake 10^7-5=10^2=100 and that gives you the strength of the stronger earthquake!
Metals are good conductors of electricity
