When the particles in a medium vibrate perpendicular to the direction the wave is traveling, this type of waves is called a:
a. transverse wave
b. longitudinal wave
c. surface wave
d. tidal wave

an ion is a charged atom or molecule. it is charged because the number of electrons do not equal the number of protons in the atom or molecule. an atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.

vapour or gas assuming atmospheriv pressure