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Oxygen gas is the second most common component of the Earth's atmosphere, taking up 20.8% of its volume and 23.1% of its mass (some 10 15 tonnes). [19] [70] [d] Earth is unusual among the planets of the Solar System in having such a high concentration of oxygen gas in its atmosphere: Mars (with 0.1% O 2 by volume) and Venus have much less. The O
To do this, the nearest noble gas that precedes the element in question is written first, and then the electron configuration is continued from that point forward. For example, the electron notation of phosphorus is 1s 2 2s 2 2p 6 3s 2 3p 3, while the noble gas notation is [Ne] 3s 2 3p 3.
The two electrons in the same orbital are closer together on average than two electrons in different orbitals, so that they shield each other from the nucleus more effectively and it is easier to remove one electron, resulting in a lower ionization energy. [2] [14] Furthermore, after every noble gas element, the ionization energy drastically drops.
For example, the electron configuration of the neon atom is 1s 2 2s 2 2p 6, meaning that the 1s, 2s, and 2p subshells are occupied by two, two, and six electrons, respectively. Electronic configurations describe each electron as moving independently in an orbital , in an average field created by the nuclei and all the other electrons.
Oxygen is the most electronegative element except for fluorine, and forms compounds with almost all of the chemical elements, including some of the noble gases. It commonly bonds with many metals and metalloids to form oxides, including iron oxide, titanium oxide, and silicon oxide.
Inert atmospheres consisting of gases such as argon, nitrogen, or helium are commonly used in chemical reaction chambers and in storage containers for oxygen-or water-sensitive substances, to prevent unwanted reactions of these substances with oxygen or water. [4] Argon is widely used in fluorescence tubes and low energy light bulbs.
A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of the chemical elements.The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases; a new row is started when chemical behavior begins to repeat, creating columns of elements with similar properties.
Each of these elements has two valence electrons in the outermost s-orbital (valence electron configuration ns 2), which is easily lost in chemical reactions to form the +2 oxidation state: thus the alkaline earth metals are rather reactive elements, with the exception of beryllium due to its small size.