网络斗地主下载

    1. <form id='hc7y7'></form>
        <bdo id='hc7y7'><sup id='hc7y7'><div id='hc7y7'><bdo id='hc7y7'></bdo></div></sup></bdo>

            <small id='x8v8f'></small><noframes id='x8v8f'>

          • <tfoot id='x8v8f'></tfoot>

              <legend id='x8v8f'><style id='x8v8f'><dir id='x8v8f'><q id='x8v8f'></q></dir></style></legend>
              <i id='x8v8f'><tr id='x8v8f'><dt id='x8v8f'><q id='x8v8f'><span id='x8v8f'><b id='x8v8f'><form id='x8v8f'><ins id='x8v8f'></ins><ul id='x8v8f'></ul><sub id='x8v8f'></sub></form><legend id='x8v8f'></legend><bdo id='x8v8f'><pre id='x8v8f'><center id='x8v8f'></center></pre></bdo></b><th id='x8v8f'></th></span></q></dt></tr></i><div id='x8v8f'><tfoot id='x8v8f'></tfoot><dl id='x8v8f'><fieldset id='x8v8f'></fieldset></dl></div>

                  <bdo id='x8v8f'></bdo><ul id='x8v8f'></ul>

                  1. <li id='x8v8f'><abbr id='x8v8f'></abbr></li>
                  2. ▸▸
                    • 🇬🇧 Helium
                    • 🇨🇳 氦
                    • 🇳🇱 Helium
                    • 🇫🇷 Hélium
                    • 🇩🇪 Helium
                    • 🇮🇱 הליום
                    • 🇮🇹 Elio
                    • 🇯🇵 ヘリウム
                    • 🇵🇹 Hélio
                    • 🇷🇺 Гелий
                    • 🇪🇸 Helio
                    • 🇸🇪 Helium

                    Helium: the essentials

                    Helium atoms have 2 electrons and the shell structure is 2. The ground state electronic configuration of neutral helium is 1s2 and the term symbol of helium is 1S0.

                    Helium: description  

                    网络斗地主下载Helium is one of the so-called noble gases. Helium gas is an unreactive, colourless, and odourless monoatomic gas. Helium is available in pressurised tanks.

                    Helium is the second most abundant element in the universe after hydrogen. α-particles are doubly ionised helium atoms, He2+.

                    网络斗地主下载Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don't try it!).

                    Helium is present in the atmosphere at about 0.0005% (1 part in 200000) by volume and is an important component within hydrocarbon gases in the USA. Its origin in these gases is traced to the decay of radioactive elements in rocks.

                    Emma's first birthday balloon is filled with helium and so rises in air.
                    网络斗地主下载Emma's first birthday balloon is filled with helium and so rises in air.

                    Helium: physical properties

                    More physical properties...

                    Helium: heat properties

                    More thermochemical properties...

                    Helium: atom sizes

                    More atomc size properties...

                    Helium: electronegativities

                    More electronegativity properties...

                    Helium: orbital properties

                    More orbital properties...

                    Helium: abundances

                    More geological data...

                    Helium: crystal structure

                    He crystal structure
                    The solid state structure of helium is: bcc (body-centred cubic).

                    More crystallographic data...

                    Helium: biological data

                    Helium has no biological role.

                    More biological data...

                    Helium: uses

                    Uses...

                    Helium: reactions

                    Reactions of helium as the element with air, water, halogens, acids, and bases where known.

                    View reactions of helium...

                    Helium: binary compounds

                    网络斗地主下载 Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of helium where known.

                    View binary compounds...

                    Helium: compound properties

                    Bond strengths; lattice energies of helium halides, hydrides, oxides (where known); and reduction potentials where known.

                    View compound properties...

                    Helium: history

                    Helium was discovered by Sir William Ramsay and independently by N. A. Langley and P. T. Cleve in 1895 at London, England and Uppsala, Sweden. Origin of name: from the Greek word "helios" meaning "sun".

                    More history...

                    Helium: isotopes

                    Isotope abundances of helium
                    Isotope abundances of helium with the most intense signal set to 100%.

                    网络斗地主下载Helium has two isotopes but it consists almost entirely of He-4 with natural He only containing just over 0.0001% of He-3. Thousands of liters of He-3 are used annually in cryogenic applications and He-3 is also used as a neutron counter in nuclear application. He-3 is also applied in magnetic resonance imaging.

                    More isotope and NMR data...

                    Helium: isolation

                    Isolation: there is very little helium on earth as nearly all present during and immediately after the earth's formation has long since been lost as it is so light. Just about all the helium remaining on the planet is the result of radioactive decay. While there is some helium in the atmosphere, currently its isolation from that source by liquefaction and separation of air is not normally economic. This is bacause it is easier, and cheaper, to isolate the gas from certain natural gases. Concentrations of helium in natural gas in the USA are as high as 7% and other good sources include natural gas from some sources in Poland. It is isolable from these gases by liquefaction and separation of from the natural gas. This would not normally be carried out in the laboratory and helium is available commercially in cylinders under pressure.

                    在线赌博最新 老虎机大全---网络斗地主下载_欢迎您 疯狂牛牛安卓---网络斗地主下载_欢迎您 娱乐正规网址-Welcome 乐酷棋牌---网络斗地主下载_欢迎您