Group 16- The Calcogens. - O, S, Se , Nonmetals; Te , metalloid; and Po metal - Have multiple allotropes: Oxygen is a gas as O 2 or O 3 ; Sulfur is a Gas as S 2 S 3 S4 Solid as S 5 to S 8 are cyclic molecules. Selenium is a solid in either Se 8 or polymeric form
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- O, S, Se, Nonmetals; Te, metalloid; and Po metal
- Have multiple allotropes:
Oxygen is a gas as O2 or O3;
Sulfur is a
Gas as S2 S3 S4
Solid as S5 to S8 are cyclic molecules.
Selenium is a solid in either Se8 or polymeric form
- Unpleasant odours
- Form one monoatomic anion (-2)
Po2+ and Po4+ also exist (radio active)
- Six valence electrons: [N.G.] ns2 np4
- Large negative ΔHelectronic attraction
“oxygen”, typically diatomic oxygen (O2),
Phases of matter:
Gas: colourless, odourless, tasteless
Liquid: pale blue explosive liquid.
Solid: pale blue and very explosive.
Strong oxidizing agent.
Reacts spontaneously with the metals of groups 1, 2 and 13; as well as some transition metals.
Some of these reactions are quite slow unless heat or a catalyst is added. Why?
Another way to increase the reactivity of gaseous O2 is to add water. Iron rusts much more quickly in damp air than in dry air!
Photo by the US EPA
- Ozone (O3) - a significant component of “smog”;
- essential component of the upper atmosphere.
- Ozone is formed from O2 in an endothermic reaction:
This reaction requires a large input of energy, i.e., from an electric current
or electromagnetic radiation from the sun.
- Ozone is unstable, decomposing to oxygen (O2). In order to maintain
constant amount of ozone, it must
continually be regenerated.
- Printer and photo copiers produce ozone
- Used as in swimming pools
Photo by the US EPA
- Ozone absorbs UV protecting organisms significant
-Ozone is broken into O2 and oxygen free radical
which reacts ozone to form O2.
-This isanexothermic process helping to moderate
the Earth’s temperature.
S. Rowland and M. Molina in 1974 first reported that
atmospheric ozone was disappearing wining them
The Nobel Prize in Chemistry in 1995.
-The “Ozone Hole” in the Antarctic was first reported
in 1985 by J. Farman, B. Gardiner, and J. Shanklin.
atoms in a puckered ring often called a crown.
This form of sulfur is insoluble in water.
(e.g. by pouring into cold water), we get
“plastic sulfur” which can be pulled into threads.
How do are these two species similar? How do they differ?
If you dissolved 1 mole of each in a liter of water, which would give you a
Solution with a lower pH?