Chemical Bonding Chapter 6 Pages 174-213

The breaking of bonds and the forming of bonds occur during chemical reactions.

Aspirin What is the formula for a molecule of aspirin? Is it an ionic or covalent (molecular) compound? What do we call the things that hold a molecule of aspirin together? C9H8O4 covalent compound (made of all nonmetals - no ions)

Aspirin C9H8O4 covalent compound (made of all nonmetals - no ions)

Aspirin (Odyssey Program) C9H8O4 covalent compound (made of all nonmetals - no ions)

The Attachment Between Atoms atoms combine to form ionic bonds covalent bonds (M + NM) (NM + NM) chemical bond – a mutual electrical attraction between the nuclei and valence electrons of two atoms that binds the atoms together

Ionic Bonding cation and anion ionic bond – electrical attraction between cations and anions; when electrons are taken by one atom from another atom metal and a nonmetal NaCl cation and anion (The charges are “hidden” to make a neutral compound.)

Ionic Bonding: taking of electrons Na 11e- F 9e- Na+ 10e- STABLE!!! F- 10e- STABLE!!! 3s 3s 2p 2p 2s 2s 1s 1s

+ - I’m Positive! I’m Negative A metal atom A metal ion A nonmetal ion A nonmetal atom I’m Positive! I’m Negative + -

Ionic bonding!!! I’m Positive! I’m Negative A metal ion A nonmetal ion I’m Positive! I’m Negative When a metal and a nonmetal atom are around each other there is the opportunity for…. …the transfer of electrons producing ions that would like to cling to each other. Ionic bonding!!!

The simplest ratio of the packed ions is called: “cubic” shape The Formula Unit Ex: NaCl

Metals form cations. (metals lose e-) Nonmetals form anions. (nonmetals gain e-)

Ions cations (+) anions (-) monatomic ions – ions formed from one atom Examples: Na+ or O-2 polyatomic ions - ions formed from two or more atoms bonded together Examples: NH4+ or SO4-2

Naming Ions monatomic ions polyatomic ions cations – named like the atom, only add ion to it Example: Na+ is the sodium ion anions – remove the ending to the atom name and add –ide and ion to it Example: Cl- is the chlorine +ide ion or the chloride ion polyatomic ions You do not determine their names, you memorize them

Ionic Compounds solid at room temperature (forming crystals) high melting points (thus are usually solid at RT) formula unit represents the lowest ratio of ions that combine to form a neutral compound when dissolved in water, the ionic compounds will break up into ions (dissociate) the solutions of ionic compounds will conduct electricity (electrolytes)

Dissociation solid placed in water hydrated ions (surrounded by water) dissociation – when an ionic compound dissolves to break apart into hydrated ions

Dissociation

Electrolytes and Nonelectrolytes When an ionic compound dissolves to produce ions, it is called an electrolyte because it conducts electricity in water. When an compound does not dissolve to produce ions, it is called a nonelectrolyte because it does not conduct electricity in water.

Electrolytes or salt?

Check for Understanding What kinds of atoms form ionic bonds? What is a polyatomic ion? Name 5 things you learned about ionic compounds.

You Try It. Do the Dissociation Equations worksheet.

Covalent Bonding covalent bond – when electrons are shared between two atoms the electronegativity difference between the two atoms is less than 1.7 usually two nonmetals NO ions formed! (no electrons are taken…just shared)

When a nonmetal and another nonmetal atom are around each other there is the opportunity for…. …the sharing of electrons producing molecules in which the atoms like to cling to each other. Covalent bonding!!!

The formation of a bond between two nonmetal atoms. Atoms sufficiently far apart to have no interaction

Figure 5 Page 179

Covalent Compounds Also called molecular compounds solid, liquid, or gas at room temperature low melting points molecular formula represents the actual ratio of atoms that combine to form a neutral compound when dissolved in water, the molecular compounds DO NOT break up into ions (NO dissociation) the solutions of molecular compounds DO NOT conduct electricity (nonelectrolytes)

The two fundamental types of bonds. Pure Covalent The two fundamental types of bonds. Ionic

There is another type of bond, not purely covalent and not purely ionic. Nonpolar Covalent Pure Covalent Polar Covalent Ionic

Sharing of Electrons How would you know if an electron is going to be taken by one atom from another? Is there ever a time in which the electron is not taken but shared? Is the electron always shared equally?

Electronegativity electronegativity – a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound The difference in electronegativity values for two atoms will indicate whether the two atoms form an ionic bond (e- taken) or a polar or nonpolar covalent bond (e- shared).

Electronegativity Differences 0.0 to 0.49 nonpolar covalent 0.5 to 1.69 polar covalent 1.7 and up ionic These ranges are flexible, although the general rule is a metal and nonmetal will form an ionic bond and two nonmetals will form a covalent bond. (Learn these values!) PS: They are different than your book!

Ionic, Polar Covalent, or Nonpolar Covalent? What kind of bond would each pair form? N and S S and C Mg and Cl C and F Ba and O Which one of these bonds has the least ionic character?

Valence Electrons valence electrons – the electrons in the highest energy level Na: 1s22s22p63s1 - 1 valence e- O: ? Ne: ? Al: ? He: ?

Octet Rule octet rule – most atoms will gain or lose electrons to have 8 valence electrons (e- in the highest energy level) Exceptions: H, He, Li, Be, B, and some atoms P and higher on the periodic table Why is an atom like Ca more stable once it becomes an ion? How many valence electrons would calcium have to lose to have 8?

Valence Shell Electron Pair Repulsion Theory VSEPR Theory Repulsion between the sets of valence-level electrons surrounding an atom causes these sets to be oriented as far apart as possible.

Regions of Electron Density What is a Region of electron density? Single bond (2e- connecting 2 atoms) Double bond (4e- connecting 2 atoms) Triple bond (6e- connecting 2 atoms) Lone pair (unbonded pair) (2e- alone on an atom)

LINEAR 180o 2 Regions of Electron Density 2 Bonds bonded pair of electrons bonded pair of electrons

TRIGONAL PLANAR 120o 3 Regions of Electron Density 3 Bonds 3 bonded pairs of electrons

BENT 119o 3 Regions of Electron Density 2 Bonds & 1 Lone Pair You don’t have to know this! BENT 119o 3 Regions of Electron Density 2 Bonds & 1 Lone Pair 2 bonded pairs of electrons 1 lone pair of electrons

TETRAHEDRAL 109.5o 4 Regions of Electron Density 4 Bonds 4 bonded pairs of electrons

TRIGONAL PYRAMIDAL 107o 4 Regions of Electron Density 3 Bonds & 1 Lone Pair 1 lone pair of electrons 3 bonded pairs of electrons

BENT 105o 4 Regions of Electron Density 2 Bonds & 2 Lone Pairs

All of these have 4 regions of electron density (although the number of bonded pairs is different)

TRIGONAL BIPYRAMIDAL 120o & 90o 5 Regions of Electron Density 5 Bonds

You don’t have to know this! SEE-SAW 120o & 90o 5 Regions of Electron Density 4 Bonds & 1 Lone Pair You don’t have to know this!

You don’t have to know this! T-SHAPED 120o & 90o 5 Regions of Electron Density 3 Bonds & 2 Lone Pairs You don’t have to know this!

You don’t have to know this! LINEAR 180o 5 Regions of Electron Density 2 Bonds & 3 Lone Pairs You don’t have to know this!

OCTAHEDRAL 90o 6 Regions of Electron Density 6 Bonds SF6

You don’t have to know this! SQUARE PYRAMIDAL approximately 90o 6 Regions of Electron Density 5 Bonds & 1 Lone Pair BrF5 You don’t have to know this!

SQUARE PLANAR 90o 6 Regions of Electron Density 4 Bonds & 2 Lone Pairs ICl4-