Explain what happens to substances during a chemical change

Consider the nuclear equation below. 239/94 pu—-> x+ 4/2 he. what is x?

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

Which of these is not an example of chemical weathering? a. iron-rich mineral rusting b. feldspar turning into clay c. limestone reacting with acid d. granite breaking up into sand