Monday, March 31, 2008

Boron vs carbon

Boron:

B
Atomic Number: 5
Atomic Mass: 10.811 amu
Melting Point: 2300.0 °C [2573.15 K, 4172.0 °F]
Boiling Point: 2550.0 °C [2823.15 K, 4622.0 °F]
Number of Protons/Electrons: 5
Number of Neutrons: 6
Classification: Metalloid
Crystal Structure: Rhombohedral
Density @ 293 K: 2.34 g/cm3
Color: Brownish
Number of Energy Levels: 2
First Energy Level: 2
Second Energy Level: 3
Isotopes: B-10, B-11
Date of Discovery: 1808
Discoverer: Sir Humphry Davy, J. L Gay-Lussac
Obtained From: Kernite

Carbon:

C
Atomic Number: 6
Atomic Mass: 12.0107 amu
Melting Point: 3500.0 °C [3773.15 K, 6332.0 °F]
Boiling Point: 4827.0 °C [5100.15 K, 8720.6 °F]
Number of Protons/Electrons: 6
Number of Neutrons: 6
Classification: Non-metal
Crystal Structure: Hexagonal
Density @ 293 K: 2.62 g/cm3
Color: Black
Number of Energy Levels: 2
First Energy Level: 2
Second Energy Level: 4
Isotopes: C-11 [20.3 minutes], C-12 [Stable], C-13 [Stable], C-14 [5730.0 years], C-15 [2.5 seconds]
Date of Discovery: Known to the ancients
Discoverer: Unknown

Gaze at the periodic table and look at all the elements and speculate why "carbon" is the basis for life as we experience it. What are the criteria for life to form? You look at the chart and wonder why carbon instead boron [ or even silicon and sulphur]. Boron is the nearest candidate but boron has problems of its own. But why just carbon? Several come to mind: The ability to have free electrons that can produce a variety of chemical bonds, the ability to replicate with DNA/RNA, and its abundance. It is quite unique that carbon has a fine chemical relationship with hydrogen, oxygen, nitrogen, phosphorus, calcium, and sulfur. The replication feature is characteristic of DNA/RNA molecules called "Linear Polymeric Molecules" and it is these molecules that are composed of simple to complex combinations of hydrogen, oxygen, nitrogen, phosphorus, calcium, and sulfur. [To note: Trace elements are also employed such as zinc, molybdenum, selenium and the biggies like sodium, potassium, and iron.] Carbon's nearest neighbor, boron, can to some degree display similar molecules but is a bit erratic in that the number of chemical bonds varies from three to six [the same for silicon and sulphur]--not predictable enough to perform replication whereas carbon bonding is always four and very reproducible. And lastly, boron for example is just not that abundant. It looks like that the chemical characteristics fill the criteria for the evolution of life.

The observation of the periodic table and a bit of cosmology yields knowledge, mystery, and awe. Just think about it...when a star is being consumed by the physics and the available elements of the star it basically stops at iron, the star bursts, and, wow, here come the other elements--one right after another. But why was carbon elected as the source for life as we know it. Well, I did offer some explanation above but it remains that it is curious that just one, just one, element was given the task. But then again, we simply don't know about life throughout the universe and some soul a billion light years away is asking: "Why is our life system based on an element with an atomic weight of 10.82?" We may want to believe that carbon-based life is universal and disappointed if we discover a multiplicity of bases.


1 comment:

Perez said...

Thought you might appreciate "The Boron Song"

http://www.youtube.com/watch?v=p9rH1_sxwQ4