1 / 10

Chapter 8: Covalent bonds

Chapter 8: Covalent bonds. Section 1: The covalent bond. Covalent bonds occur when nonionic compounds share electrons Molecules are formed when 2 or more atoms bond covalently Electrons are shared between both atoms Never occur with metals! ONLY nonmetals and metalloids form covalent bonds.

chesna
Download Presentation

Chapter 8: Covalent bonds

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. Chapter 8: Covalent bonds

  2. Section 1: The covalent bond • Covalent bonds occur when nonionic compounds share electrons • Molecules are formed when 2 or more atoms bond covalently • Electrons are shared between both atoms • Never occur with metals! ONLY nonmetals and metalloids form covalent bonds

  3. The covalent bond (cont.) • The bond occurs because the attraction of the nucleus of one atom to the electrons of another atom is greater than the repulsion of the nuclei and electrons of both atoms. Called maximum net attraction. • If the atoms get too close the repellant forces push the atoms away from each other and NO bond forms • The unpaired electrons of both atoms are shared between the atoms

  4. Single covalent bonds • A single covalent bond occurs when only one pair of electrons is shared between two atoms. • For example: • 1 single covalent bond: Hydrogen gas (H2) • 2 single covalent bonds: Water (H2O) • 3 single covalent bonds: Ammonia (NH3) • 4 single covalent bonds: Methane (CH4)

  5. Single covalent bonds (cont.) • Sigma bonds () are another term for a single covalent bond but also occur when the pair of shared electrons is centered between the atoms. • PRACTICE PROBLEMS: • Page 244 • #1-5 • Homework if not finished in class

  6. Multiple covalent bonds • Occur when more than one pair of electrons are shared. • Double bonds- 2 pairs of shared electrons • Oxygen gas (O2) • Triple covalent bonds- 3 pairs of electrons are shared • Nitrogen gas (N2) • Pi bonds () are when the shared electrons occur in overlapping parallel orbitals • Multiple bonds always have one  bond and at least one  bond

  7. Strength of bonds • Determined by three main things: • Bond length • Size of the atoms • # of electrons that are shared • Increasing bond length decreases bond strength • Increasing atomic size decreases bond strength • Increasing the # of shared electron pairs increases the bond strength

  8. Bonds and energy • The creation of a covalent bond releases energy • The destruction of a covalent bond requires energy • Bond dissociation energy(BDE)is the energy required to break a covalent bond • Chemical potential energy is the value of the BDE for all bonds in a molecule added together

  9. Bonds and energy (cont.) • Endothermic reactions require more energy to break bonds than is produced when new bonds form. Overall net input of energy. • Exothermic reactions release more energy when bonds are formed than is required to break bonds apart. Overall net output of energy.

  10. Assessment • Page 247 • # 7-13 • Homework unless finished in class • Quiz tomorrow over section 1

More Related