1 / 20

Chemical Bonding

Chemical Bonding. Masterton 2011. Introduction. Knowledge of IE and EN form the basis of our understanding of bonding. bonding refers to the _________________ _____________- between pairs of atoms/ions There are four types of bonds

yitro
Download Presentation

Chemical Bonding

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemical Bonding Masterton 2011

  2. Introduction • Knowledge of IE and EN form the basis of our understanding of bonding. • bonding refers to the _________________ _____________- between pairs of atoms/ions • There are four types of bonds ________, _________, _________ ___________ and __________

  3. Ionic lattice structure • Ionic compounds are made up of ions • Metal and non-metal • These positive and negative ions attract each other and group together in structures called____________.

  4. Ionic lattice structure cont. • extremely difficult structures to _____________. • Thus all ionic substances are ___________with _____________________________. • +500 °C • There is one method of breaking up the lattice - dissolve the ionic compound in ____________ • Water separates the ions and allow them to move freely as a solution.

  5. Illustrating Ionic bonding – Lewis Dot Diagrams Method 1) core is represented by the symbol for the element, valence e-are represented by dots 2) 4 sides and the valence e-are distributed around the sides 3) When distributing valence e-, first place one dot on each of the sides before pairing up e- on any one side.

  6. Formation of Ionic Compounds 1. Draw Lewis dot diagram of every atom in the molecule Tips: Draw atom in with fewest e- in the middle Ex: MgCl2 2. Draw a circle around the single e-that will be moved to the other atom 3. Draw an arrow from the donating atom’s e-to the receiving atom 4. Draw square brackets and charge around the resulting ions and e-

  7. Cl Cl Mg -1 +2 -1 Cl Cl Mg Formation of Ionic Compounds This is what should be shown when asked for the formation of an ionic compound Ex: MgCl2

  8. Covalent compounds • no ions. • atoms join up by sharing e-with their neighbours. • groups or clusters of atoms called ________________. • non-metal to non-metal • Pure covalent – atoms of _________________

  9. covalent compounds have _______ ______________________. • exist either as ________(like methane), ____________(like water) or as easily melted __________(like paraffin wax).

  10. Covalent Molecules Shared Electrons = bonds Single bond: 1 pair of shared e- Double bond: 2 pairs of shared e- Triple bond: 3 pairs of shared e- Examples Note: Non-bonding e- are “Lone Pairs”

  11. Covalent molecules cont. • covalent bonds inside the molecules are very strong. • Intramolecular forces (joining atoms together) • the molecules don't break apart easily. • the forces attracting neighbouring molecules to each other are very weak, thus very easy to separate molecules from one another: e.g. ammonia • Intermolecular forces (attraction between molecules)

  12. When a covalent compound melts or boils, it is the forces between the molecules which are broken. • Very little energy is needed to make this happen, so covalent substances have ________________ _________________________points.

  13. Covalent network structures • exceptions • Diamond, graphite, the element silicon and silicon dioxide are examples of covalent substances with very high melting points. • These substances don't exist as __________. Instead they have giant network structures - something like the ionic lattices, except that the bonds are all covalent. • need a large amount of E to break strong covalent bonds, so very high melting points. • _______________ in water - they are not broken apart by trying to dissolve them.

  14. Formation of Covalent Molecules 1. Draw Lewis dot diagram of every atom Ex: H2O 2. Draw a circle around 2 e-, one e- belonging to one atom and another e- belonging to the other atom 3. Draw a line to replace circled pairs of electrons

  15. H O H H O H Formation of Covalent Molecules This is what should be shown when asked for the formation of a covalent molecule Ex: H2O

  16. Polar Covalent Bonds • e- pairs not always shared _____________ between atoms. • Unequal sharing accounts for many aspects of chemical behaviour. • HCl H – ______ Cl – _______ ∆EN = • H has a lower EN than Cl therefore the electrons will be closer to the Cl. • (Remember- EN is the ability to attract electrons in a chemical bond) • Thus, the charge is distributed slightly unevenly throughout the molecule. This is a _______________________________

  17. Ionic, Covalent or Polar Covalent Electronegativity can determine whether a molecule is ionic or covalent or polar covalent DEN = [EN value of one atom] - [EN value of another atom]

  18. Metallic Bonds • Metals in the solid state consist of an array of the metal cations sharing all the valence e- from all the cations • The electrons are said to be “___________________” (not being associated with any particular cation) and are free to _________________________. • Known as

  19. Metallic bonding cont. • Sulphur is easily ground • Tin can be flattened but not broken • Magnesium is not easily broken up

  20. Summary

More Related