Science MCQs

Nitrogen gas (N₂) has a triple bond between the two nitrogen atoms.

Methane consists of one carbon atom (valency 4) bonded to four hydrogen atoms (valency 1 each).

NaCl is the chemical formula for sodium chloride commonly known as table salt.

Cl⁻ (Chloride ion) is a single atom with a charge making it a monatomic ion not polyatomic.

A covalent bond is the force that holds two atoms together through the mutual sharing of electrons.

The charge on the ion directly indicates its valency. Cu²⁺ has a valency of 2+.

A double covalent bond involves two shared pairs of electrons. 2 pairs x 2 electrons/pair = 4 electrons total.

Sodium is a metal. Metals tend to lose electrons to form positive ions (cations).

Sodium ion is Na⁺. Hydroxide ion is OH⁻. Their valencies are both 1 so the formula is NaOH.

Fe²⁺ has lost 2 electrons while Fe³⁺ has lost 3 electrons. The number of protons remains the same.