1. C HAPTER 17- H OW A TOMS B OND AND M OLECULES A TTRACT The Big Idea: Atoms and molecules are sticky

2. 17.1 E LECTRON -D OT S TRUCTURES Valence electrons= electrons in outermost shell Electron- dot structures: a series of dots surrounding an atomic symbol Electron-dot structures help us understand ionic and covalent bonds Nonbonding pairs= electrons that are relatively stable and are already in pairs

3. 17.2 T HE F ORMATION OF I ONS Ion - an element w/ a net electric + or – charge, caused by a loss(+) or gain(-) of electrons Atoms tend to gain/loose electrons to have a filled outermost shell The periodic table tells us the type of ion each atom tends to form.

4. 17.3 I ONIC B ONDS An ionic bond is the electric force of attraction between two oppositely charged ions. Ionic compounds form when 2 ions come together to create a compound. - Ionic compounds have different properties than the ions from which they were made.

5. T HE C HEMISTRY OF M INERALS For all ionic compounds, positive and negative charges must balance. Ionic bonds usually form from elements on opposite sides of the periodic table Ex: Aluminum oxide. Al +3 + O -2 = Al 2 O 3

6. 17.4 M ETALLIC B ONDS Metallic bond- when metal ions are held together by freely flowing electrons. -This accounts for metal’s ability to conduct electricity and heat, as well as it’s ability to be bent and shaped. An alloy is a mixture or two or more metallic elements

7. 17.5 C OVALENT BONDS Covalent bonding is when atoms are held together by a mutual attraction to the electrons they share. Covalent compounds is when 2 or more substances are held together by covalent bonds. This forms a molecule. - Chemists use a straight line to symbolize two electrons involved in a covalent bond

8. # of covalent bonds an atom can form= # of electrons needed to fill it’s outermost shell

9. 17.6 P OLAR C OVALENT BONDS Electronegativity- how strongly an atom can tug on bonding electrons. Dipole- separation of charge that occurs in a chemical bond b/c differences in electronegativity of bonded atoms The greater an atom’s electronegatvivity, the greater it’s ability to pull electrons towards itself when bonded.

10. A nonpolar bond happens when no dipole is formed because the two atoms have relatively the same electronegativity Polar bonds form when a very electronegative atom and a weakly electronegative atom are covalently bound. -The further away elements are from each other on the periodic table, the larger difference they have in electronegativity.

11. 17.7 M OLECULAR P OLARITY When dipoles go in the opposite direction with equal strength, they cancel out and the molecule is nonpolar

12. 17.8 M OLECULAR A TTRACTIONS The strength of the strongest attractions is still weaker than chemical bonds

13. Ion-dipole: bond between an ion and polar dipole molecule Dipole-dipole: bond between 2 polar molecules. - Ex of strong dipole-dipole: hydrogen bond.- When H bonds to N,O, or F - Reason why water had such high boiling point Dipole-induced dipoles: temporary uneven distribution of electrons