Is concrete a compound element or mixture?

Which of these properties, used alone, would be least useful in identifying most minerals? a. color b. luster c. streak d. density

Is a pencil falling to the floor anon contact force, a force, or a contact force

Astable electron arrangement for an atom is one that does not easily change. how is this arrangement arrived at? a. valence electrons are transferred or shared to create a full outer shell of electrons. b. valence electrons are discarded into space to create a full outer shell of electrons. c. protons (positive charge) pair with valence electrons (negative charge) to create a strong bond. d. outer shells with valence electrons are transferred or shared.