It can fit two more electrons within its valence shell to follow the octet rule. It will have a -2 charge to gain those two electrons to fill its octet.
The chemical bonds in CH4 are all single bonds. C only can bond 4 times because it needs 8 electrons in it's outer shell and only has four right now. The bonds represented are all single bonds because there are two electrons present on each side of the carbon. Two electrons, in this case, equals one bond.
From Earth's<span> density we can estimate what elements must compose the </span>Earth; an iron core<span> just happens to estimate </span>Earth's<span> mass the best. Now from energy waves, geologists use seismometers to measure movements in </span>Earth's<span> interior (e.g. Earthquakes), These energy-waves form compressional and shear waves</span>