The unit of length most suitable for measuring the thickness of a cell phone is a ( megameter, meter, millimeter, nanometer ) the unit of length most suitable for measuring the height of a backyard tree is a ( megameter, meter, millimeter, nanometer ).

1.millimeter 2.meter

Explanation:

a phones thickness can be measured with such a small measurement and a tree is not big enough for a megameter but not small enough for a millimeter so it'd be a meter

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.