Mercury is the only metal that is liquid at normal temperatures.

Answer: C) Lead(II) oxide Explanation: The systematic name for a chemical is the unique name given to it by the International Union of Pure Applied Chemistry (IUPAC). The IUPAC name can differ from a chemical compound's general name.   PbO is an ionic compound since it consists of a Lead as metal and Oxygen as nonmetal. The systematic name for PbO is Lead (II) oxide. Here we need to put the (II) since lead has more than one combining capacity.

Ionic bonding is a type of chemical bond in which valence electrons are lost from one atom and gained by another.. This bond generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion.   Example :: One example of an ionic bond is the formation of sodium fluoride, NaF, from a sodium atom and a fluorine atom. In this reaction, the sodium atom loses its single valence electron to the fluorine atom, which has just enough space to accept it. The ions produced are oppositely charged and are attracted to one another due to electrostatic forces.