When a certain rock formed, it contained 12 mg 40k. the rock now contains 3 mg 40k. the half-life of 40k is 1.3 billion years. how old is the rock? your answer is in billions of years and should be a number only and include the tenth decimal place (e. g., 23.8 not 23.81 or 23?

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

What are the similarities of physical and chemical change ?

The chemical bond connecting one nucleotide with the next one along the nucleic acid chain is called a