General Chemistry Exam 2 Review

Chapters 4, 5, 6, 7

What is an ionic bond?

metal (cation) + nonmetal (anion)

transfer atoms from one to another

What is a covalent/molecular bond?

nonmetal + nonmetal

share electrons between atoms 

What is a metallic bond?

metal + metal

Empirical Formula

Relative # of atoms of an element in a compound

Molecular Formula

Exact # of atoms of an element in a compound

Predict ionic charges by…

1. Find the charge of the ion based on place in the periodic table

2. Use ‘cross and drop’

Name ionic compounds by…

cation first, anion second

Binary compounds…

…contain 2 elements

Polyatomic ions…

…groups of 2 or more atoms of different elements bonded together with a general charge

Mono…

1

Di…

2

Tri…

3

Tetra…

4

Penta…

5

Hexa…

6

Hepta…

7

Octa…

8

Nona…

9

Deca…

10

Percent composition

(molar mass of element in compound / total molar mass of compound) * 100

How to find Empirical and Molecular Formula from percentages/mass…

1. Convert percentages to grams

2. Convert grams to moles

3. Divide all by the smallest # of moles to obtain a ratio

4. Multiply to make whole #’s 

Bonding pairs…

…link 2 atoms together

Lone pairs…

…are a pair of valence electrons not involved in bonding, create a ‘cloud’

Polar covalent

Bonding electrons are shared unequally

Pure covalent/Nonpolar covalent

Electrons are shared equally

Ionic bonds

transfer all electrons, full charges on resulting ions 

Formal Charges

(valence electrons) - (lone pair electrons) - (bonding electrons/2)

Bond Order 

½ (# bonding electrons - # antibonding electrons)

Bond order doesn’t exist if ….

… the bond order = 0 

Sigma bonds

First formed bonds between 2 atoms

Stronger than Pi bond

Head-to-head overlap

Pi bond

Second/third formed bond in a double/triple bond

Density of electrons above and below place of nuclei 

Bonding MO

Electron density is concentrated between two nuclei and draw atoms together

Antibonding MO

Electron density is avoidant of space between nuclei and destabilize the bond

As bond order increases…

…bond stability increases

As bond energy decreases…

…the bond length decreases

As bond stability increases…

…bond energy decreases

As bond length decreases…

…bond order increases 

Reactants

Left side of a chemical equation

They REACT to form a product 

Product

Results of the reactants after a chemical reaction

Stoichiometry

Study of numerical relationship between chemical qualities and reactions 

Stoichiometric calculations must…

…obey the law of conservation of mass!

Gas state of reactant/product…

(g)

Liquid state of reactant/product…

(aq)

Solid state of reactant/product…

(s)

Combustion

Type of chemical reaction involving O₂ and heat

Limiting reactant/reagent

the reactant completely consumed in the chemical reaction that limits the final amount of the product made

Reactant in excess 

the reactant that occurs in greater quantity than expected to be necessary to complete the chemical reaction (NOT the limiting reactant)

Theoretical yield

amount of product that can be made based on limiting reactant

Actual yield

amount of product actually produced (will be provided to you in the prompt or will be found through a lab)

Percent yield

(actual yield / theoretical yield) * 100