The simple view of the bonding in methane You will be familiar with drawing methane using dots and crosses diagrams, but it is worth looking at its structure a bit more closely. There is a serious mis-match between this structure and the modern electronic structure of carbon, 1s 2 2s 2 2p x 1 2p y 1.
Lack of sun exposure: Lack of sun exposure is a major cause of low vitamin d level especially if you live in the northern us. Less likely would be lack of vitamin d in food, but also a possibility if you are on a very restrictive diet.
I encourage everyone to get their Vitamin D Level checked because up to 85% of the population has a Low Vitamin D Level, and most people are absolutely shocked at HOW LOW their vitamin d level is. Then the next question from them is, Why Do I have Vitamin D Deficiency!. Eating a very low fat diet-vitamin d is fat soluble and you must have fat to absorb it. 2  Having very dark skin-blocks the UV rays from reaching the cells that make vitamin d in the skin. 3  Living in the far North (or far South in the Southern Hemisphere).