Where more than one isotope exists, the value given is the abundance weighted average.Ītoms of the same element with different numbers of neutrons. This is approximately the sum of the number of protons and neutrons in the nucleus. The mass of an atom relative to that of carbon-12. The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.ĭensity is the mass of a substance that would fill 1 cm 3 at room temperature. The temperature at which the liquid–gas phase change occurs. The temperature at which the solid–liquid phase change occurs. The arrangements of electrons above the last (closed shell) noble gas. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f). The atomic number of each element increases by one, reading from left to right.Įlements are organised into blocks by the orbital type in which the outer electrons are found. Members of a group typically have similar properties and electron configurations in their outer shell.Ī horizontal row in the periodic table. About 99.76% of oxygen is oxygen-16.A vertical column in the periodic table. This is why the atomic weight of oxygen (15.9994) is so close to 16. Oxygen made a good choice for the standard before much was known about isotopes because although there are 3 natural isotopes of oxygen, most of it is oxygen-16. Oxygen was the atomic weight standard for the other elements until 1961 when it was replaced by carbon 12.It's the molecule of primary importance, as far as generating bright and colorful auroras. Excited oxygen is responsible for the bright red, green, and yellow-green colors of the aurora.As stars burn hydrogen and helium, oxygen becomes more abundant. Oxygen is also the most abundant element in the Earth's crust (about 47% by mass) and the third most common element in the Universe. Although there are more hydrogen atoms in the body than oxygen atoms, they account for significantly less mass. This makes it the most abundant element, by mass, in the body. Much of that oxygen is part of water, H 2O. Approximately 2/3 of the mass of the human body is oxygen.Oxygen is paramagnetic, which means it is weakly attracted to a magnet but doesn't retain permanent magnetism.Oxygen supports combustion. However, it is not truly flammable! It is considered an oxidizer.

A single atom of oxygen usually has an oxidation number of -2. Singlet oxygen may be found in the upper atmosphere. Ozone, O 3, is another form of pure oxygen. Atomic oxygen, which is also called 'singlet oxygen' does occur in nature, although the ion readily bonds to other elements. Oxygen gas normally is the divalent molecule O 2.The atoms readily gain electrons and form covalent chemical bonds. The solid form is brittle rather than malleable or ductile. Oxygen is a nonmetal. It has low thermal and electrical conductivity, but high electronegativity and ionization energy.Liquid and solid oxygen is pale blue. At lower temperatures and higher pressures, oxygen changes its appearance from blue monoclinic crystals to orange, red, black, and even a metallic appearance.Oxygen gas is colorless, odorless, and tasteless. It's usually purified by fractional distillation of liquefied air, but the element is found in many compounds, such as water, silica, and carbon dioxide.Symptoms of oxygen poisoning include vision loss, coughing, muscle twitching, and seizures. At normal pressure, oxygen poisoning occurs when the gas exceeds 50%. Plant photosynthesis drives the oxygen cycle, maintaining it around 21% in air. While the gas is essential for life, too much of it can be toxic or lethal.

Animals and plants require oxygen for respiration.

Oxygen atomic number