CHAPTER 17- HOW ATOMS BOND AND MOLECULES ATTRACTThe Big Idea: Atoms and molecules are sticky

17.1 ELECTRON-DOT STRUCTURES

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

17.2 THE FORMATION OF IONS

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 periodictable tells us the type of ion each atom tendsto form.

17.3 IONIC BONDS

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.

THE CHEMISTRY OF MINERALS

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= Al2O3

17.4 METALLIC BONDS

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

17.5 COVALENT 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

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

17.6 POLAR COVALENT 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.

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.

17.7 MOLECULAR POLARITY

When dipoles go in the opposite direction with equal strength, they cancel out and the molecule is nonpolar

17.8 MOLECULAR ATTRACTIONS

The strength of the strongest attractions is still weaker than chemical bonds

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