Chemical Bonding: Ionic Bonding

Chemical Bonding: Ionic Bonding

• Ionic bonding involves the transfer of electrons between atoms
• Atoms want full valence electron shells
• A chemical bond forms when a new arrangement of electrons has less energy than the previous arrangement
• Ionic compounds have high melting points compared to molecular compounds due to strong electrostatic forces between ions.
• Ionic compounds are typically solids at room temperature
• Ionic compounds conduct electricity when dissolved in water
• Lewis diagrams show only valence electrons in an atom
• Valence electrons interact when atoms bond to form molecules
• Lewis structures are drawn by writing the element symbol, then drawing dots, one for each valence electron around the symbol. Spread the dots over four sides before pairing them. The placement of the dots is flexible.
• Electronegativity is a measure of an atom's ability to attract electrons in a bond.
• Electronegativity follows the same trend as ionization energy
• Electronegativity generally increases across a period and decreases down a group.
• A difference in electronegativity greater than 1.7 indicates an ionic bond.

Crystal Lattices

• Ionic compounds form crystal lattices.
• Atoms in crystal lattices pack tightly in regular, repeating patterns.
• Oppositely charged ions attract each other and stack in a crystal lattice (repeating pattern)
• A crystal lattice example is NaCl (sodium chloride)

Dissolving Ionic Compounds in Water

• When dissolved in water, the ions are pulled out of the lattice and surrounded by water molecules.
• This allows the ions to move freely, enabling the solution to conduct electricity.
• When an ionic compound dissolves in water, the ions in the crystal lattice are separated and surrounded by water; the ions will be free to move.

Electrolytes

• Ionic compounds dissolved in water are electrolytes
• Electrolytes conduct electricity because the ions are free to move around.

Homework

• Page 60, problems 1 through 9