Molecules and Ions
- Chemical bonds:
forces that hold atoms together in compound.
- Covalent bond
formed
by sharing electrons.
- Molecule:
collection
of atoms bonded by covalent bonds Example:
H2, H2O, O2, NH3, CH4
- Chemical Formula consist
of element symbol and subscripts to indicate the relative number of atoms. Example:
CO2
- In structural formula individual
bonds are shown by lines.
- Ionic bond:
Electrostatic attraction between ions.
- Ion: atom or group of atoms that net
charge: Monoatomic
ion: Example:
Na+ and Polyatomic
ion:NH4+
- Ionic
compound such as sodium chloride: NaCl.
- Sodium atom loses electron to form positive ion Na+; called cation.
- Chlorine atom gain electron to form negative ion Cl- called anion.
In NaCl equal number of Na+ and Cl- ion packed together and form
beautiful colourless cubic crystals.
Ionic solid consist of oppositely
charged ions.