1. CONCURRENT ENROLLMENT
CHAPTER 4
CONCURRENT ENROLLMENT

2. LEWIS STRUCTURE
Elemental symbol represents the nucleus and core electrons
Dots represent the valence electrons
Mg, Cl, C
Octet rule
Ionic bonds
Na+ + Cl-  NaCl
Page 100 learning check

3. IONIC COMPOUNDS
Ions are atoms that have gained or lost electrons so now they have a charge.
Ions cannot be found alone in nature, they have to be in a compound
Metals are reactive because they lose valence electrons easily.
Nonmetal ions gain the number of electrons required to fill an octet.
Some nonmetals can gain or lose electrons to complete an octet.

4. Positive Ion Formation
A positively charged ion is called a cation.
This figure illustrates how sodium loses one valence electron to become a sodium cation.

5. Negative Ion Formation
An anion is a negatively charged ion.
The figure shown here illustrates chlorine gaining an electron to become a chlorine ion.

6. CONTINUED Isoelectronic species? Ionic compounds
P3-, S2-, Cl-, Ar, K+, Ca 2+
Ionic compounds
The positive ion total charge has to cancel out the negative ion total charge to form a compound
Mg 2+ (2+ total charge) + 2Cl- (you need 2 chloride ions to get a total charge of 2-) = MgCl2

7. IONS Binary compounds have only single atom ions Polyatomic ions
Covalently bonded groups of atoms that have a charge
Formula mass, CO2

8. Properties of Ionic Compounds
Positive and negative ions exist in a ratio determined by the number of electrons transferred from the metal atom to the non-metal atom.
In a solid, ions are locked into position and electrons cannot flow freely—solid ions are poor conductors of electricity
Liquid ions or ions in aqueous solution have electrons that are free to move, so they conduct electricity easily.
An ion in aqueous solution that conducts electricity is an electrolyte.
The repeating pattern of particle
packing in an ionic compound is
called an ionic crystal

9. CONTINUED Stable form of an ionic compound is a crystal
A crystal lattice is the three-dimensional geometric arrangement of oppositely charged ions, and is responsible for the structure of many minerals.

10. METALLIC BONDING
The electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electrons.
The electrons are free to move around and are referred to as delocalized electrons, forming a metallic cation.
A metallic bond is the attraction of an metallic cation for delocalized electrons.
metal atoms valence electrons move freely through empty or partly empty sublevels these are called CONDUITS

11. POLARITY Electronegativity Bond polarization
Shared electrons being attracted to the more electronegative atom
The chemical bond that results from sharing electrons is a covalent bond.
A molecule is formed when two or more atoms bond covalently.
The majority of covalent bonds form between atoms of nonmetallic elements.

12. Polar molecules and ionic substances are usually soluble in polar substances.
Non-polar molecules dissolve only in non-polar substances.

13. DIATOMIC
Diatomic molecules (H2, N2, F2, O2, I2, Cl2, Br2) exist because the two-atom molecules are more stable than the individual atoms

14. CONTINUE Polar molecule
Polarized bonds where the charge are distribute unevenly throughout the molecule
Nonpolar molecule
No polarized bonds or polarized bonds where the charges are distributed evenly throughout the molecule
Table 4.5 page 121

16. EXAMPLES Nonpolar compounds are named using Greek prefixes
All nonpolar compounds named will have no more than two elements in it
The second element ends in –ide
mono- is never used with the first element
CO and CO2

17. NAMING ACIDS
Binary Acids (An acid that contains hydrogen and one other element) – Ex. HCl
The first word has the prefix hydro- to name the hydrogen part of the compound. The rest of the word consists of a form of the root of the second element plus the suffix–ic, HCl (hydrogen and chlorine) becomes hydrochloric.
The second word is always acid, Thus, HCl in a water solution is called hydrochloric acid.

18. OXYACIDS
An oxyacid is an acid that contains both a hydrogen atom and an oxyanion. Ex. HNO3
Identify the oxyanion present. The first word of an oxyacid’s name consists of the root of the oxyanion and the prefix per- or hypo- if it is part of the name and a suffix. If the oxyanion’s name ends with the suffix –ate, replace it with the suffix –ic. If the name of the oxyanion ends with suffix –ite, replace it with suffix –ous, NO3 the nitrate ion, becomes nitric.
The second word of the name is always acid, HNO3 (hydrogen and nitrogen ion) becomes nitric acid.

19. TABLE

20. Molecular Structures Structural Formulas
A structural formula uses letter symbols and bonds to show relative positions of atoms.

21. VSEPR THEORY
Lone pairs (electrons) take up more space than when bonded, this will change the bond angles
Hybrid sublevels
3 atoms/ 2 bonded electron pairs sp
4 atoms/ 3 bonded electron pairs sp2
5 atoms/ 4 bonded electron pairs sp3

22. TYPE GEOMETRY BOND ANGLE
AB2 (2 e- pairs) Linear o example on board
AB3 (3 e- pairs) Triangular 120o example on board
Planar
AB (4 e- pairs) Tetrahedral 109.5oexample on board
AB2E (2 e- pairs, Bent example on board
1 lone pair)
AB2E2 (2 e- pairs, Bent o example on board
2 lone pairs)
AB3E (3 e- pairs, Triangular 107o example on board
1 lone pair) Pyramidal

25. Molecular Structures Resonance Structures
Resonance is a condition that occurs when more than one valid Lewis structure can be written for a molecule or ion.
This figure shows three correct ways to draw the structure for (NO3)-1.

26. Molecular Structures
Two or more correct Lewis structures that represent a single ion or molecule are resonance structures.
The molecule behaves as though it has only one structure.
The bond lengths are identical to each other and intermediate between single and double covalent bonds.

27. Exceptions to the Octet Rule
Some molecules do not obey the octet rule.
A small group of molecules might have an odd number of valence electrons.
NO2 has five valence electrons from nitrogen and 12 from oxygen and cannot form an exact number of electron pairs.
A few compounds form stable configurations with less than 8 electrons around the atom—a suboctet.

28. Exceptions to the Octet Rule (cont.)
A coordinate covalent bond forms when one atom donates both of the electrons to be shared with an atom or ion that needs two electrons.
A third group of compounds has central atoms with more than eight valence electrons, called an expanded octet.

29. INTERPARTICLE FORCES Forces that keep particles together Network solid
Solids composed of only atoms interconnected by a network of covalent bonds are called covalent network solids.
Quartz and diamonds are two common examples of network solids.

30. CONTINUED Dipolar forces
The force between two oppositely charged ends of two polar molecules is a dipole-dipole force.
A hydrogen bond is an especially strong dipole-dipole force between a hydrogen end of one dipole and a fluorine, oxygen, or nitrogen atom on another dipole.

31. WATER
The red line represents hydrogen bonds

32. CONTINUED
Covalent bonds between atoms are strong, but attraction forces between molecules are weak.
The weak attraction forces are known as van der Waals forces.
The forces vary in strength but are weaker than the bonds in a molecule or ions in an ionic compound.
Non-polar molecules exhibit a weak dispersion force, or induced dipole.

33. PROPERTIES Many physical properties are due to intermolecular forces.
Weak forces result in the relatively low melting and boiling points of molecular substances.
Many covalent molecules are relatively soft solids.