Option d: copper.
Because copper is an element, not a mixture.
Oxygen has six valence (outer-shell) electrons so therefore gains two more electrons to form the O-2 ion Its electron configuration is: 1s2 2s2 2p6 or Ne
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Answer: Either A or D
Geologists and paleontologists constructed the geologic table based on the relative positions of different strata and fossils, and estimated the time scales based on studying rates of various kinds of weathering, erosion, sedimentation, and lithification.
iodine which should appear before tellurium and argon which should appear after potassium
There is a 3rd one: nickel should appear before cobalt
They meet all the environmental conditions an organism needs to survive
