Which of the following best describes a mixture? 1) a substance that is made up of several different molecules.
2) a substance that is made up of only one molecule
3) a substance that is made up of only one compound.
4)a substance that is made up of only one element.

Esign techniques and materials that reduce the negative environmental impact of a structure are referred to as

Which of the following is always a reactant in a combustion reaction? oxygen nitrogen hydrogen carbon

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