1 / 18

Introduction to Chemical Bonding and Chemical Formulas

Learn about valence electrons, major bond types, electronegativity differences, and how to write chemical formulas in this comprehensive guide to chemical bonding concepts.

chancock
Télécharger la présentation

Introduction to Chemical Bonding and Chemical Formulas

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. Introduction to Chemical Bonding and Chemical Formulas Ch. 6, Sec. 1 Ch. 7, Sec. 1

  2. Valence Electrons are…? • The electrons responsible for the chemical properties of atoms, and are those in the outer energy level. • Valence electrons - The s and p electrons in the outer energy level • the highest occupied energy level • Core electrons– are those in the energy levels below.

  3. Introduction to Bonding • Chemical bond: mutual electric attraction between nuclei and valence electrons of differing atoms that “hold” them together as a compound. • Results in a reduction of the potential energy of the system, thereby becoming more stable • Major types: ionicand covalent • The bond type depends on the atoms’ electronegativities

  4. Major Bond Types • Ionic bond- electrons are transferred between atoms; cations attract anions. • Covalent bond: electrons are shared between two atoms • Nonpolar= atoms shared equally (mostly) • Polar= atoms shared unequally

  5. Ionic vs. Covalent

  6. Electronegativies Figure 20 on page 161

  7. More • Subtract the electronegativities to determine the nature of the bond • If the difference is greater than 1.7, the bond is ionic • ΔEN of 1.7 is about 50% ionic character • If the difference is from 0 to 0.3, the bond is non-polar covalent. • If the difference is from 0.3 to 1.7, the bond is polar covalent.

  8. Character of BondsFigure 2 on page 176 About 50% ionic character

  9. Nonpolar-Polar-IonicFigure 3 on page 177

  10. Summary • If the atoms have very differentelectronegativities, then ionic bonding occurs ( Metal and Nonmetal) • If they both have high electronegativities, then covalent bonding occurs (Two nonmetals) • If they both have low electronegativities, then metallic bonding occurs (Two metals)

  11. Practice: What kind of bond? • Na and Cl • Sr and O • C and O • Ni and Fe • N and O • Br and Br • Ti and Cr • ionic • ionic • polar covalent • metallic • polar covalent • non-polar covalent • metallic

  12. Keeping Track of Electrons • Atoms in the same group have the same outer electronic structure and therefore the same number of valence electrons. • The number of valence electrons is easily determined. It is the group number for groups 1 and 2 • Group 1: H, Li, Na, K, etc. have 1 valence e- • Group 2: Be, Mg, Ca, etc. have 2 valence e-

  13. More about Keeping Track • For elements in groups 13-17: • Subtract 10 from the group number • This is the number of valence electrons

  14. Chemical Formulas • A unit of matter composed of two or more nonmetal atoms is a molecule. • A chemical formulais an expression of the number of atoms of each element in a compound. • The chemical formula of sulfuric acid is H2SO4.

  15. Writing Chemical Formulas • The number of each type of atom in a molecule is indicated with a subscript in a chemical formula. • If there is only one atom of a certain type, no “1” is used. • A molecule of vitamin B3 has 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom. What is the chemical formula? C6H6N2O

  16. Interpreting Chemical Formulas • Some chemical formulas use parentheses to clarify atomic composition. • Ethylene glycol, a component of some antifreezes, has a chemical formula of C2H4(OH)2. It contains 2 carbon atoms, 4 hydrogen atoms, and 2 OH units, for a total of 6 hydrogen atoms and 2 oxygen atoms. How many total atoms are in ethylene glycol? • Ethylene glycol has a total of 10 atoms.

  17. Formulas • How many atoms of carbon are in NaCH3COO • 2 • How many atoms of nitrogen are in NH4NO3? • 2 • How many calcium atoms are in C12H22O11? • 0 • How many oxygen atoms are in Co(NO3)2? • 6 • How many atoms are in Al2(SO4)3? • 17

  18. Using Formulas • How many oxygen atoms in the following? CaCO3 Al2(SO4)3 • How many ions in the following? CaCl2 NaOH Al2(SO4)3 3 atoms of oxygen 12 (3 x 4) atoms of oxygen 3 total ions (1 Ca2+ ion and 2 Cl1- ions) 2 total ions (1 Na1+ ion and 1 OH1- ion) 5 total ions (2 Al3+ + 3 SO42- ions)

More Related