A covalent bond is formed by 2 non metals sharing 1, 2 or 3 pair of electrons. Which of the following atom pairs will form an ionic bond?
The correct answer and explanation is:
Sure! To determine which atom pairs form ionic bonds, we need to understand the nature of ionic vs covalent bonding:
- Covalent bonds form when two nonmetals share electrons.
- Ionic bonds form when a metal and a nonmetal interact, resulting in transfer of electrons from the metal to the nonmetal, creating positively and negatively charged ions.
Example atom pairs (hypothetical):
- Na and Cl
- O and H
- C and O
- Mg and O
Which form ionic bonds?
- Na (metal) and Cl (nonmetal) → Ionic bond
- Mg (metal) and O (nonmetal) → Ionic bond
- O and H (both nonmetals) → Covalent bond
- C and O (both nonmetals) → Covalent bond
Explanation:
Ionic bonds occur when there is a large difference in electronegativity between two atoms, typically between metals and nonmetals. Metals tend to lose electrons easily because they have low ionization energies, forming positively charged ions (cations). Nonmetals have higher electronegativity and gain electrons, forming negatively charged ions (anions). This transfer of electrons creates electrostatic attraction between the oppositely charged ions, resulting in an ionic bond.
For example, sodium (Na) is a metal with one electron in its outer shell. Chlorine (Cl) is a nonmetal with seven electrons in its outer shell. Sodium transfers its one valence electron to chlorine, producing Na⁺ and Cl⁻ ions. The strong electrostatic force between these ions forms the ionic bond in sodium chloride (NaCl).
In contrast, when two nonmetals like oxygen (O) and hydrogen (H) interact, they have similar electronegativities and tend to share electrons rather than transfer them. This electron sharing forms covalent bonds, as seen in water (H₂O).
Magnesium (Mg) is a metal that readily loses two electrons, and oxygen is a nonmetal that gains two electrons. Thus, magnesium oxide (MgO) is another classic example of an ionic compound.
Summary:
- Metal + Nonmetal = Ionic bond (electron transfer).
- Nonmetal + Nonmetal = Covalent bond (electron sharing).
Thus, Na and Cl and Mg and O form ionic bonds.