Which of the following statements is true for radioactive reactions: a) They are affected by pressure
b) They are affected by temperature
c) They release huge amounts of energy
d) Nucleus of the element does not change during the react

The answer for #3 is c but i don't know why

Which statement describes both homogeneous mixtures and heterogeneous mixtures?

1)each group 16 element has how many valence electrons? ( )4 ( )6 ( )8 ( )16 2)how many dots appear in the dot structure for calcium ion, ca2+? ( )zero ( )one ( )two ( )eight 3) which of the following atoms forms a cation to obtain an octet of outer shell electrons? ( )magnesium ( )oxygen ( )fluorine ( )helium 4) an al3+ ion contains 13 protons and 10 electrons. ( )true ( )false 5) valence and non-valence electrons are represented in lewis dot structures. ( )true ( )false