Question

which pair of elements will form an ionic bond?
carbon and oxygen
nitrogen and oxygen
barium and chlorine
carbon and chlorine
question 4
which pair of elements will form a covalent bond?
lithium and oxygen
potassium and chlorine
aluminum and chlorine
carbon and sulfur
question 5
in the formula for water h₂o, what does the subscript 2 indicate?
two oxygen atoms in the compound
two atoms in the compound
two hydrogen atoms in the compound
two molecules in water

Explanation:

• Ionic bond: Ionic bonds form between a metal and a non - metal. Barium (\(Ba\)) is a metal (Group 2 alkaline earth metal) and chlorine (\(Cl\)) is a non - metal (Group 17 halogen). In the formation of an ionic bond, barium donates electrons (becomes \(Ba^{2+}\)) and chlorine accepts electrons (becomes \(Cl^{-}\)).
• Covalent bond: Covalent bonds form between non - metals. Carbon (\(C\)) and sulfur (\(S\)) are both non - metals. They share electrons to form a covalent bond.
• Subscript in \(H_2O\): In the chemical formula \(H_2O\), the subscript applies to the element immediately before it. So, the subscript \(2\) next to \(H\) indicates that there are two hydrogen atoms in one molecule of water.

Answer:

• For the ionic bond question: barium and chlorine.
• For the covalent bond question: carbon and sulfur.
• For the \(H_2O\) subscript question: two hydrogen atoms in the compound.