Coordinate Covalent Bonds In covalent bond, how many electrons does each atom supply? Covalent bond in which one atom contributes both bonding electrons Most polyatomic cations and anions contain covalent and coordinate covalent bonds!
Example What are some important chemical elements for plants growth? In fertilizer, Ammonium is a nitrogen source.
To represent CCB shown by an arrow arrow points from the atom donating the lone pair to the atom accepting it.
Let’s practice! Write Lewis Dot Structure of SO2 1)Figure out number of valence electron and number of electrons that it need to fulfill octet! 2)arrange atoms so that structure satisfy the octet of all three atoms
Let’s practice! Try NO
Earlier we mentioned… That fertilizer contains Ammonium salts. But plants can’t use Ammonium directly Needs to be converted into nitrate!
Bond dissociation energy To convert it and form new compounds, it need to break bonds Def) amount of energy need to break bonds More energy needed to break bonds>>product is more stable than reactants/stronger bonding Look at table 16.3 on pg 448 Which bond is strongest? What happens to bond length as bond length? What pattern do you see?
Resonance Structure Occur when it is possible to write two or more valid electron dot formulas that have the same number of electron pairs for a molecule or ion. resonance structures are not real Resonance structures are not in equilibrium with each other. Resonance structures are not isomers Resonance structure only move ELECTRONS!
Example
Exceptions to Octet rule Electron deficient molecules-atoms that have less than 8 electrons Ex) hydrogen, beryllium, boron Compounds with odd number of valence electrons don’t fulfill octet ex) NO2>>17 total ve Some atoms can expand octet and include ten or twelve electrons Ex)phosphorous, sulfur
magnetism What is happening to electron when atoms form bonding? Electrons are spinning in opposite directions>>create magnetic field Diamagnetic; all electrons are paired Paramagnetic; lone pairs Which element is paramagnetic? Be, He, Li, N