1 / 24

Chemical Bonding

Chemical Bonding. Chapter 7. Chemical Bonds. Chemical Bond – a link between atoms resulting from the neutral attraction of their nuclei for electrons force of attraction between atoms. Ionic bond.

libba
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 Chapter 7

  2. Chemical Bonds • Chemical Bond – a link between atoms resulting from the neutral attraction of their nuclei for electrons • force of attraction between atoms

  3. Ionic bond • Ionic Bond – chemical bond resulting from the transfer of electrons from one bonding atom to another • Ex. NaCl • Ionic Bonds form ionic compounds which are composed of ions.

  4. Characteristics of an ionic bond • -high melting points (shows a strong bond) • -brittle • -dissolve in water • -good conductors of electricity in solution

  5. Octet Rule • Octet Rule – atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons. • Example of an ionic bond: • Consider NaCl – (table salt) • Na – 1s22s22p63s1 • Cl – 1s22s22p63s23p5

  6. What happens? • Na loses 1e- to form an octet • becomes Na+ ion • called CATION • Cl gains 1e- to form an octet • becomes Cl- ion • called ANION

  7. Using Lewis Dot diagrams • used to show valence electrons • dot represents valence electrons (or x’s and o’s) • random order • Na Cl -> Na+ + Cl -

  8. Formulas • Empirical Formula – chemical formulas which gives the simplest whole number ratio of atoms of elements in a compound. • -cation ALWAYS written first • -total “+” must equal total “-“

  9. Monoatomic ions – made of ONLY 1 element • Must remember the charge of the ion • Cations: Anions: • Group 1: +1 Group 17: -1 • Group 2: +2 Oxide: -2 • Silver: +1 Sulfide: -2 • Zinc: +2 Nitride: -3 • Aluminum: +3 Phosphide:-3

  10. Polyatomic ions • -ions which consist of more than one atom • they act as a whole and carry a net charge • Examples of Polyatomic Ions • Hydroxide - OH- Acetate – C2H3O2- • Hypochlorite – ClO- Sulfate – SO4-2 • Nitrate – NO3- Carbonate – CO3-2 • Bicarbonate – HCO3- Phosphate – PO4-3

  11. Binary Compounds • Binary Ionic Compounds • - contain ions of only 2 elements. • - Need to know the ratio of elements in compound

  12. Writing formulas: Criss-Cross method • write symbols of the elements or polyatomic ions putting the charge as a superscript • put parenthesis around only the polyatomic ion • crisscross the numbers not the charges and represent as subscripts

  13. Writing formulas…. • reduce if possible • eliminate and rewrite any subscript of 1 and any parenthesis whose subscript is 1. • Example: Na and O form • Na2O

  14. Covalent Bonds • Covalent Bond – chemical bond resulting from the sharing of electrons between bonding atoms • Ex. CO2

  15. 7.2 Covalent Bonds • Molecule- a group of atoms grouped together by covalent bonds. • Molecular substance – a substance made up of molecules.

  16. Molecular vs. Empirical • Molecular formula – tells you how many atoms are in a single molecule of the compound. • Ex. C6H12O6 glucose • The empirical formula can be written for molecular formulas. • Ex. CH2O glucose

  17. Formulas • Structural formula – shows which atoms bond in a molecule. • - Lewis Structures • - Based on the Lewis Dot diagrams • - The electrons between the 2 elements are the shared electrons.

  18. Ex: F2 and NH3 • Unshared pair – Electrons needed to satisfy the octet • Note: H is an exception. It can only hold 2 e-s

  19. Single Covalent bond – 2 atoms share exactly one pair of electrons • Double Covalent bond – 2 pairs of shared bonds (4 electrons between 2 atoms) • Ex. H2CO • Triple Bond – there will be 6 dots (electrons) between 2 atoms • Note: Use a line to indicate a bond (or 2 electrons). Use dots to show electrons that are unshared.

  20. Exceptions • Exception to the octet rule • Atoms with less than an octet - Boron • Ex. BF3 • Atoms with more than an octet - Sulfur • Ex. SF4

  21. Properties of covalent bonds • Properties of Covalent Bonds • Bonds can be polar depending on the Electronegativity of the atoms. • If one atom is significantly more electronegative than the other, the electron density will change.

  22. The atom that is more electronegative will pull the electrons closer to it and cause a partial negative on that atom. • **Electronegative difference must be between 0.5 and 1.9 • If the electronegatives are similar, the bond will be nonpolar (electronegative difference less than 0.4)

  23. Ionic bonds Involves transfer of electrons • Forms ions • Usually forms between metal and nonmetal and/or polyatomic atom • substances usually soluble in water • high melting point

  24. solutions are usually good conductors of electricity • compounds are brittle • formulas are expressed as empirical formulas • 9.Electronegativity difference greater than 1.9 • 10.strong bond • 11. criss cross

More Related