Why is the electrical charge of an atom zero or neutral?

Because the atom isn't a isotope. The electrons, (negative charge) , and the protons, (positive charge), balance each other out. 

1.from liquid state to gaseous state is evaporation 3.solid to liquid is melting 5. solid to gaseous state is sublimation 6. gas to solid state is decomposition 7. a change of state is known as the states of matters

Temperature and pressure