The Navajo are the second largest tribe in the U.S. and they have the largest reservation stretching across Colorado, Utah, New Mexico and Arizona with over 25,000 square miles. They were also among the largest group of Indians to migrate to Los Angeles in the 1950s and 60s.
The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth, stretching from a height of about 50 km (31 mi) to more than 1,000 km (620 mi).
The nucleus contains two kinds of particles: neutrons, which have no charge, and positively charged protons. Negatively charged particles called electrons orbit around the nucleus in different layers, or orbitals. (Unlike this diagram, there is a vast space between the nucleus and the electron orbitals.