endothermic means it absorbs energy while exothermic means it releases energy. remember this.
There is an unstable ratio of protons and neutrons. Because protons are positively charged but neutrons have no charge, an increase in the number of protons means there needs to be an increase in the number of neutrons to "bind" the nucleus together. This is because like charges repel, so the protons will repel each other, and if there aren't enough neutrons to act as "glue" to hold the nucleus together, the nucleus will break apart.
Wegener suggested that perhaps the rotation of the Earth caused the continents to shift towards and apart from each other. (It doesn't.) Today, we know that the continents rest on massive slabs of rock called tectonic plates. The plates are always moving and interacting in a process called plate tectonics.
