Chemistry: Electron Arrangement in Water Molecules

Electron Arrangement of Water Molecule

• The oxygen atom in a water molecule has six outer electrons, with two involved in covalent bonds to the hydrogens and four existing in nonbonded pairs (lone pairs).
• The lone pairs are excellent hydrogen bond acceptors, and the half-filled orbitals participate in the formation of a sigma bond between oxygen and hydrogen atoms.
• The electron arrangement around oxygen assumes a tetrahedral geometry.

Polarity of O-H Bonds

• The electronegativity difference between oxygen and hydrogen results in unequal sharing of electrons, making hydrogen partially positive and oxygen partially negative.
• The O-H bonds are polar, making the OH groups in water strong hydrogen bond donors and acceptors.

Hydrogen Bonding in Water

• Each water molecule can form hydrogen bonds with four other water molecules due to the bond angles.
• The additive effect of hydrogen bonds results in water having a well-ordered structure, explaining its internal cohesion and unusual properties.

Unusual Properties of Water

• Water has a high boiling point, high heat of vaporization, high viscosity, high surface tension, and high dielectric constant compared to other compounds of similar molecular weight.
• These properties are due to the extensive hydrogen-bonded network of water.

Properties of Water

• Water has a high boiling point for its molecular weight (18) compared to other molecules.
• Water's unusual properties include its high heat of vaporization, high viscosity, high surface tension, and high dielectric constant.

Structure of Ice

• When water molecules freeze, the hydrogen bonding becomes regular and clearly defined, creating a rigid tetrahedral molecular lattice in which each molecule is hydrogen-bonded to four others.
• The open structure of the ice lattice accounts for water's unusual property of being less dense as a solid than as a liquid.

Biological Importance of Water

• Water serves as the universal intracellular and extracellular medium due to its remarkable solvent ability.
• The ability arises from water's tendency to form hydrogen bonds and its dipolar character.
• Hydrophilic substances, which can take advantage of water's properties, can readily dissolve in water.