Chest radiograph. A chest radiograph, colloquially called a chest X-ray (CXR), or chest film, is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in medicine.
Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.he nucleus of the helium-4 atom is identical with an alpha particle. High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud.
The atomic number is what distinguishes one element from another in nature. For example, hydrogen has an atomic number of 1. An atom of hydrogen has a single proton and a single electron. Helium has an atomic number of 2.A single helium atom has 2 protons and 2 electrons. Copper has an atomic number of 29, so it contains 29 protons and 29 electrons.The atomic weight (sometimes called atomic mass) of an atom is approximated by the sum of the number of protons and the number of neutrons in the nucleus of the atom.he atomic number is what distinguishes one element from another in nature. For example, hydrogen has an atomic number of 1. An atom of hydrogen has a single proton and a single electron. Helium has an atomic number of 2.