BONDING, GEOMETRY, IMF TEST TOPICS
Representative Particles – ELEMENT-Atom
COVALENT or MOLECULAR COMPOUND-Molecule
IONIC COMPUND -Formula Unit
IONIC BONDING
Ionic Compound formation
Exothermic process – why?
Lattice energy – charge and distance between ions
Lattice Energy overcomes Ionization Energy and electron Affinity considerations
Crystalline Lattice
Ionic Compounds have very high MP and BP
They are also rigid because the transferred valence electrons are not free to move from atom to atom.
Solubility Lab
Lattice Energy and solubility
COVALENT BONDING
Covalent bonds
Br2 I2 N2 Cl2 H2 O2 F2
Lewis Structures – Follow the steps!
Exceptions -- More than an octet – period 3,4,5,6,7
Less than octet – H (duet rule) Be (quartet rule) and B (hextet rule)
Also, remember that halogens won’t double bond when they are most
electronegative element in molecule.
VSEPR
Electron Domains
EDG, MG, angles
Resonance Structures – due to delocalized pi bonds
Bond Polarity -- Ranges from nonpolar covalent to polar covalent all the way to ionic
Molecular polarity – 6 Rules/generalizations given in class
Application – Marker chromatography, soap, cotton etc (“polar and nonpolar”)
Hybrid orbitals – 2 issues -- 1) # of bonds and 2) identical bonds
Promotion and hybridization solves these issues.
Evaporation Lab
Dipole-dipole force, H-bond, and LDFs
(These are all known as van der Waal’s attractions/forces)
IMF -- Ionic bonds, ion-dipole, Dipole-dipole, H-bond (super strong DD force),
and LDFs (based on size/# of electrons in molecule)
Big Polar Molecules -- Hi BP, Hi MP, Slow Evaporating Rate
Small Nonpolar Molecules -- Low BP, Low MP, Fast Evaporating Rate
Like Dissolves Like
(i.e. polar substances mix well with other polar substances;
non-polar substances mix well with other non-polar substances) WHY???
Multiple bonding
Sigma bonding (always localized) and Pi bonding (sometimes localized and sometimes delocalized –
Pi bonding is delocalized if resonance structures are possible)
COVALENT NETWORK SOLIDS
A crystalline structure held together by COVALENT BONDS! (not ionic)
Leads to extremely high MP (e.g. Diamond [C] and Quartz [SiO2])
Even higher MP’s than Ionic Compounds!
METALS
Metallic Bonding
Cations amidst a sea of mobilized valence electrons (causes malleability, luster, conductivity)
Most metals have rather high MP and BP.