Transcript Periodic Properties II PreLab

Periodic Properties: Groups 5A, 6A, and 7A
A.
Group 5A
1. Elements and Symbols
a. N = Nitrogen
b. P = Phosphorous
c. As = Arsenic
d. Sb = Antimony
e. Bi = Bismuth
2.
Element Type
Non-metal
Non-metal
Metalloid
Metalloid
Metal
State
diatomic gas
solid
solid
solid
solid
Some chemistry of the non-metal Group 5A Elements
a. The elements tend to react to gain 3 electrons to be like noble gas
b. These elements react with oxygen to form acidic compounds
HNO3 = Nitric Acid
H3PO4 = Phosphoric Acid
P4(s) + 5 O2(g) -----> P4O10(s)
P4O10(s) + 6 H2O -----> 4 H3PO4(aq)
c. Important Biological Elements
N is a component of every amino acid (protein) and DNA
P is a component of DNA
d. Phosphorous has more than one allotrope
- Allotrope = stable solid phase
- P4(s) is called “white phosphorous” is tetrahedral, and burns in air
- Pred is called “red phosphorous” and is made of chains of P4
tetrahedra
- Pblack is called “black phosphorous” and is a crystalline solid
e. We will be reacting Red Phosphorous with Oxygen today in lab
- Don’t bother with the bottle
- Burn the phosphorous in the bunsen burner in the hood
- Have a distilled water dampened piece of pH paper ready
- Put the pH paper (green when damp) in the phosphorous smoke
- If it turns red, that indicates the formation of acid
- DON’T PUT HOT COMBUSTION SPOON INTO BOTTLE!!!
B. Group 6A
1. Elements and Symbols
a. O = Oxygen
b. S = Sulfur
c. Se = Selenium
d. Te = Tellurium
e. Po = Polonium
Element Type
Non-metal
Non-metal
Non-metal
Metalloid
Metalloid
State
diatomic gas
solid
solid
solid
solid
2. Some chemistry of the non-metal Group 5A Elements
a. The elements tend to react to gain 2 electrons to be like noble gas
b. 20% of the atmosphere and 50% of the crust is O (by mass)
c. These elements react with oxygen to form acidic compounds
d. Sulfuric Acid (H2SO4) is the largest volume chemical used in industry
- S(s) + O2(g) -----> SO2(g)
- SO2(g) + H2O(l) -----> H2SO3(aq) = sulfurous acid
e. We will be burning S(s) in the hood to produce H2SO3
- Use same procedure as for phosphorous
- All waste P and S should be completely burned off of the spoon
f. Sulfur has more than one Allotrope
- Two allotropes of solid sulfur have 8-membered rings, but
different crystal forms: “monoclinic” and “rhombic”
- If liquid sulfur is cooled quickly, it solidifies as chains of sulfur
atoms called “plastic sulfur”
monoclinic
rhombic
plastic
C. Group 7A = Halogens
1. Elements
a. F = Fluorine
b. Cl = Chlorine
c. Br = Bromine
d. I = Iodine
e. At = Astatine
Element Type
Non-metal
Non-metal
Non-metal
Non-metal
Non-metal
(kJ/mol)
State
E.A.
diatomic gas, yellow
-328
diatomic gas, yellow
-349
diatomic liquid, brown
-325
diatomic solid, purple
-295
radioactive solid
2. The chemistry of these elements is dominated by their need to add one e2 Na(s) + Cl2(g) -----> 2 NaCl(s) + large amount of heat
Sodium Reacts
Violently with
Chlorine
3. Electron Affinity = energy given off when a gaseous element gains an ea. X(g) + e- -----> X-(g)
b. Exothermic process because all elements accept e- due to + nucleus
c. Adding e- is less favored down a group due to distance from nucleus
d. Fluorine is so small, that repulsion from other electrons lowers its E.A.
4. Halogens with more favorable E.A. can take electrons from other halides
a.
Cl2 + 2 Br- -----> 2 Cl- + Br2
b. E.A:
-349
-325
c. Cl2 is reduced; Br- is oxidized
5. We will be studying this kind of reaction today in lab
a. Prepare control samples:
- I2/H2O + toluene = purple color of I2 in toluene
- Br2/H2O + toluene = orange color of Br2 in toluene
- Cl2/H2O + toluene = yellow color of Cl2 in toluene
I2
Cl2
Br2
b. Run all possible combinations of reactions between Cl/Br/I and
observe the color of the toluene when finished
Cl2 + Br- -----> yellow (Cl2) if no reaction; orange (Br2) if reaction
Cl2 + I- ----->
Br2 + Cl- ----->
Br2 + I- -----> orange (Br2) if no reaction; purple (I2) if reaction
I2 + Cl- ----->
I2 + Br- ----->
c. Use parafilm to cover test tubes to shake them up
d. All halogen reactions go into a waste beaker in the hood
Incident: HF and Trifluoroacetic Acid Burn
Incident: HF Exposure