Molecular compounds

Molecular bonds are bonds betwee nonmetals. They have covalent bonds.

Ionic compounds transfer electrons from metal to nonmetal. Molecular compounds share them

Covalent bonds are when they share electrons instead of transferring. Atoms with unpaired electrons are shared to make a full outer shell.

\ce{H2}, \ce{O2}, \ce{F2}, \ce{Br2}, \ce{I2}, \ce{N2}, \ce{Cl2}

These are never found alone. They always come in pairs. This only applies when they are by themselves–not when they are bound to another element.

Dashes represent bonds. = for double bonds. \chemfig{O(-[1]H)(-[7]H)}

Molecular structures are visual representations of how atoms in a molecule are connected by bonds. When drawing them:

1. Count valence electrons
   • Determine the total number of valence electrons for all atoms in the molecule.
   • Remember: each bond (single, double, or triple) uses 2 electrons.
2. Arrange atoms
   • The least electronegative atom (except hydrogen) usually goes in the center.
   • Hydrogen and halogens are almost always on the outside.
3. Connect atoms with bonds
   • Start with single bonds between the central atom and surrounding atoms.
   • Use double or triple bonds if needed to satisfy the octet rule.
4. Distribute remaining electrons
   • Add lone pairs to satisfy each atom’s octet (or duet for hydrogen).
5. Check formal charges
   • Ensure the molecule is neutral or has the correct charge. Adjust double/triple bonds as necessary.

Tips for finding bonds:

• Look at the number of unpaired valence electrons for each atom—they indicate how many bonds it can form.
• Hydrogen forms 1 bond, Oxygen forms 2, Nitrogen forms 3, Carbon forms 4.
• Use the total number of electrons to confirm the number of bonds: \[ \text{Total bonds} = \frac{\text{Total valence electrons needed} - \text{Electrons available}}{2} \]
• Start with single bonds and adjust to double/triple bonds if any atoms don’t have a full outer shell.

Example: Water, \ce{H2O}, has 2 single bonds between oxygen and hydrogen: \chemfig{O(-[1]H)(-[7]H)}