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Covalent and Ionic Bonds

Covalent and Ionic Bonds. Elizabeth Varvel BHS Chemistry. Chemical Bonds. Chemical bonds form when the valence electrons of atoms join to make a complete octet. Nobel gases are the only elements that satisfy the octet rule without forming compounds.

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Covalent and Ionic Bonds

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  1. Covalent and Ionic Bonds Elizabeth Varvel BHS Chemistry

  2. Chemical Bonds • Chemical bonds form when the valence electrons of atoms join to make a complete octet. • Nobel gases are the only elements that satisfy the octet rule without forming compounds. • As atoms bond, potential energy decreases and atoms form more stable arrangements.

  3. Types of Bonds • Ionic Bond: formed of metal + nonmetal or metal + polyatomic ion. • Covalent Bond: formed of nonmetal + nonmetal. • Polar Covalent = unequal sharing of electrons b/t atoms • Non-Polar Covalent = equal sharing of electrons b/t atoms. • Metallic Bond • Metal atoms form a special type of bond with each other called a metallic bond. • The “electron sea” model shows that in a metallic bond, mobile electrons are shared by all atoms.

  4. What's a covalent compound?I'm sure glad you asked!  • In a covalent compound the atoms that are bonded share electrons rather than transfer electrons from one to the other.  • covalent compounds are formed when two nonmetals bond to each other

  5. "Why do elements share electrons? • Nonmetals have to share electrons with each other due to electronegativity. • Electronegativity is how strongly an element pulls electrons away from other elements • All nonmetals have roughly the same electronegativity. So.. neither element can steal electrons from the other as a result they'll have to share electrons rather than transfer them.

  6. Electronegativity Difference & Bond Type • Electronegativity difference • 0 to 0.3  nonpolar covalent • 0.3 to 1.8  polar covalent • 1.8 & up  ionic

  7. Non-Polar –vs- Polar Non-Polar Covalent: Each of the atoms equally attracts the shared electrons. Polar Covalent: Atoms in a compound attract electrons unequally. i.e.: Oxygen has a greater electronegativity than hydrogen and pulls electrons more towards itself more.

  8. High melting point High boiling point Electrically conductive Form a formula unit Metal + nonmetal (or metal + polyatomic ion) Electrons are donated and accepted—not shared Brittle Hard (crystalline solid) Low melting point Low boiling point Electrically non-conductive Form a molecule Nonmetal + nonmetal Electrons are shared Strong Exist as solids, liquids, or gases Ionic Compounds -vs- Covalent Compounds Ionic Covalent

  9. Most covalent compounds have small molecules. They are gases, liquids or solids, most with low melting & boiling points. Chlorine Cl2 - a gas Iodine I2 - a liquid Carbon Dioxide CO2 – a gas Water H2O – a polar molecule http://www.youtube.com/watch?v=Kj3o0XvhVqQ

  10. Naming Compounds • All covalent compounds have two word names.  The first word stays the same and the second has "-ide" is substituted for the end.  • HF is named "hydrogen fluoride",. • If there is more than one atom of an element in a molecule, we need to add prefixes to these words to tell us how many are present. 

  11. Mono - 1 Di – 2 Tri – 3 Tetra – 4 Penta – 5 Hexa – 6 Hepta – 7 Octa – 8 Nona – 9 Deca - 10 P2O5 diphosphorus pentoxide CO carbon monoxide CF4 carbon tetrafluoride

  12. Practice

  13. exceptions to this naming • these names are so common that they're officially recognized H2O is "water" NH3 is "ammonia" CH4 is "methane

  14. VSEPR—a theory that applies to nonmetals • VSEPR: valence-shell electron-pair repulsion • VSEPR theory states: • “Repulsion between the sets of valence-electrons surrounding an atom causes these sets to be oriented as far apart as possible.” • VSEPR can help determine molecular shape or molecular geometry

  15. VSEPR and Molecular Geometry

  16. Intermolecular Forces • Intermolecular Forces A. Join two or more molecules together B. Weaker than ionic bonds, covalent bonds, or metallic bonds. C. There are three types of intermolecular forces: 1. Hydrogen bonding, • Dipole-dipole interactions, • London-dispersion forces.

  17. Strength of Forces of Attraction from Strongest to Weakest • Chemical Bonds • a. Nonpolar Covalent • b. Polar Covalent • c. Ionic • Intermolecular Forces (Van der Waals Forces) • a. Hydrogen Bonding • b. Other Dipole-Dipole Forces • c. London Dispersion Forces

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