On the periodic table as you go from the bottom left hand corner towards the top right corner atoms increase in electronegativity. Electronegativity is how much an atom wants to 'hog' electron(s). Oxygen is in the air that exists everywhere on Earth. Why is it that cars rust when paint chips off of then?
Now that the protective coat of paint is gone, the iron (Fe) in the car is exposed to oxygen (O2) and water (H20) (moisture in the air, rain etc). It readily undergoes a chemical reaction because oxygen's more electronegative than iron and really 'wants' irons electrons. This reaction forms rust also known as iron oxide (2Fe2O3) and the chemical formula is as follows: 4Fe+ 3O2 → 2Fe2O3
All known organisms on Earth are made of matter (atoms) and have to build their bodies from said matter. As humans everything we eat is used to build our cells, tissues, organs and our whole bodies. We take matter in the shape of food, break it down and use those atoms to build our bodies. So an interesting question that peaked my interest popped into my head one day. Trees have bodies mainly made of carbon atoms. Where does the carbon come from? Where are trees getting these carbon atoms to build their bodies?
Trees cannot be taking the carbon out of the soil. If they did, every time a tree grew from a seed to a mature adult an equal amount of soil would vanish as the tree would absorb/eat the soil and use those atoms to build itself. The tree cannot obtain carbon from sunlight or water (H20). The tree is getting the carbon from the air. It breaths in carbon dioxide (C02) and releases oxygen as a byproduct. It takes the carbon atom from the carbon dioxide molecule and uses that to build itself.
In the observable universe astronomers have observed, that most light arriving on Earth from the majority (billions) of galaxies appears to be shifted red (looks redder than it is). However, a few close by galaxies appear to have their light shifted towards the blue end of the light spectrum. What does this shift in the light spectrum mean?
This phenomena is known as red shift and it is one piece of evidence that tells us that the Universe is expanding, with most galaxies moving away from us. When an object is moving towards an observer it's light waves are compressed and this makes the lights frequency increase. Whereas, if an object is moving away from an observer the light that reaches the observer will have a lower frequency as it is decompressed (stretched). Blue light has a higher frequency than red light. Meaning that the waves of light, for blue, are more compressed than for red. So if most galaxies we observe have a light spectrum that is moved/shifted towards red (lower frequency and compression as compared to blue) then most galaxies are moving away from us. This leads us to conclude that the Universe is expanding. However, it also tells us that a few galaxies, ones that have their light shifted towards blue, are moving towards us.