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Chemical Bonding: The Force That Holds Atoms Together

A chemical bond is the force that holds atoms together, involving only valence electrons. Atoms gain or lose electrons to achieve stability according to the Octet Rule. There are intermolecular forces between neighboring molecules and intramolecular forces within a molecule. Chemical bonds can be ionic (metal and nonmetal) or covalent (nonmetals sharing electrons). Ionic compounds like salt (NaCl) have high melting and boiling points, conductivity, and solubility, while covalent molecules like O2 are gases with lower melting and boiling points and are non-conductive. Understanding oxidation numbers and naming ionic compounds aid in studying chemical bonding.

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Chemical Bonding: The Force That Holds Atoms Together

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  1. Not that type of bonding! BONDING! CHEMICAL BONDING!

  2. A chemical bond is the force that holds two or more atoms together. • Only valence e- are involved in a chemical bond. • Octet Rule: Atoms will gain, lose, or share electrons with another atom to have 8 valence electrons and be stable. Use the force! Believe in the force!

  3. Two types of forces: • Intermolecular forces = an attractive force between two neighboring molecules. • Intramolecular forces = attractive force within one molecule. + - + -

  4. Two types of chemical bonds: • Ionic Bonds = stronger bond made of metal and nonmetal  formed when atom gains or loses e- to get full octet • Covalent Bonds = weaker bond made of two or more nonmetals  formed when atom shares e- to get full octet

  5. loss/gain e- share e- metals and nonmetals 2 or more nonmetals solid crystal lattice, hard, brittle liquid or gas high MP & BP lower MP & BP usually insoluble soluble (able to dissolve) conductive* not conductive

  6. Common Examples • Salt – (NaCl) – is an ionic compound. How do we know this? • Na = metal (left of staircase) salt crystal • Cl = nonmetal(right of staircase) ionic compound • Salt’s Properties: • Solid crystal lattice • MP is 1473F; BP is 2669F (VERY HIGH) • Conductive • Soluble in water

  7. Common Examples • Oxygen we breathe is actually O2 which is a covalent molecule. How do we know this? • O = nonmetal (right of staircase) covalentmolecule • Oxygen’s Properties: • gas • MP is -361F; BP is -297F (very low) • Non conductive

  8. I EIGHT, I’m FULL, I’m HAPPY! Remember: Reactivity between atoms is based on getting a full octet – which ever way is best for that atom: either gaining e-, losing e-, or sharing e-.

  9. Ionic Compounds Only Metal Atoms: lose e- to become positively charged cations ionic bond Nonmetal Atoms: gain e- to become negatively charged anions

  10. When the positive metals and negative nonmetals come together, they form an ionic bond. Ionic bonds: attraction between oppositely charged ions (a metal and a nonmetal)

  11. Oxidation Numbers tion # + + • The number of electrons an atom loses or gains to get a full octet creates the oxidation number for an element!

  12. Note: It is easier to lose 1, 2, or 3 electrons than to gain 5, 6, or 7 electrons!

  13. the group number = the number of valence e- = which helps you figure out the ox. # for group A elem. • THIS DOES NOT WORK FOR THE TRANSITION METALS OR INNER TRANSITION METALS!

  14. Oxidation Numbers for the Group A Elements 3+ 1+ 2+ 1- 0 3- 2- NA

  15. Write the ions formed for: Sr+2 • Strontium • Arsenic • Potassium • Iodine • Note: Only nonmetals change their names when bonding to have an ending of –ide. As-3 called arsenide in a compound K+1 or K+ I-1 or I- called iodide in a compound

  16. Label the Compounds as Ionic or Covalent MgCl2 _________ CCl4 _________ H2 _________ Al2S3 _________ ionic metal + nonmetal covalent two nonmetals covalent two nonmetals ionic metal + nonmetal

  17. Label the Compounds as Ionic or Covalent carbon dioxide ___________ potassium bromide ___________ aluminum iodide ___________ covalent two nonmetals ionic metal + nonmetal ionic metal + nonmetal

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