Why is copper extracted from ores containing low percentage of copper compounds

Achef makes salad dressing by mixing oil, vinegar, and spices, as shown. which type of matter is the salad dressing?

This active feature of earth's crust in building mountain ranges as well as islands. this feature is a a) cavern. b) earthquake. c) mountain. d) volcano.

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