Amedium of free floating positive and negative charges are called ?

Plasma

Explanation:

Mostly this occurs at very high temperatures that cause atoms to lose electrons. Plasma is therefore a gas but of ions. Plasma can conduct electricity and can be influenced by magnetic fields. Plasma occurs mostly in stars where it is the dominant state of matter.  

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer