Helium, He is a gas at room temperature and is colourless, tasteless, odorless and is not poisonous.

    Atomic Number - 2

    Weight of a Helium atom - 4.002602g/molˉ1（Weight per Helium atom）

    Melting point is- ?272.20 °C

    Boiling point is- ?268.93 °C

    This means that Helium can exist as a liquid but the temperature is would have to reach would be near absolute zero which is at the moment physically impossible.

    Even though Helium is relatively rare on Earth it is the second most abundant element in the Universe（as we know it）, because of nuclear fusion of hydrogen in stars more helium is being produced. On Earth helium is mainly found by the radioactive decay of radioactive elements. Helium is given off as α alpha radiation as ionised Helium particles.

    Helium was first discovered by a French astronomer on the 18th of August 1868 during a total solar eclipse when a bright yellow line 587.49 nanometers was discovered.

    Alpha particles were shown that they are helium nuclei by scientist Ernest Rutherford in1907.

    The main use of helium was mainly to replace the use of hydrogen gas in zeppelins as hydrogen was extremely flammable. The use that many people know of however is for pumping up party balloons, but some other uses are to use for welding （the helium used for this must be extremely pure） and helium can be mixed with hydrogen and used as a laser.

    Helium is found in stars and is reacted through Nuclear Fusion to make the other elements found throughout the Universe.

    氦，He 在室溫下是一種氣體，無色，嘗不出也聞不到，無毒。

    原子序數(shù)-2

    氦原子的質(zhì)量-4.002602克/摩爾（每個氦原子的質(zhì)量）

    （譯者注：4是氦的相對原子量，氦原子的質(zhì)量約是6.6969*10^-27 kg）

    融解溫度- -272.20°C

    沸騰溫度- ?268.93 °C

    就是說，氦只有在接近絕對零度的時候才以液態(tài)存在，而絕對零度目前是無法達到的。

    （譯者注：絕對零度無法達到，但接近是可以達到的。）

    盡管氦在地球上比較稀有，它在宇宙中卻是第二號最豐富的元素（就我們所知）,原因是恒星中氫的核聚變會形成氦。在地球上，氦主要發(fā)現(xiàn)在放射性元素的放射性衰變中。阿爾法衰變會產(chǎn)生一個離子化的氦離子，就這樣得到了氦。

    （譯者注：地球上氦雖然少，也是自然廣泛存在的，可以工業(yè)提純制造的。）

    氦最初由法國天文學(xué)家在1868年8月18日發(fā)現(xiàn)，在一次日全食中，發(fā)現(xiàn)了587.49納米的亮黃線。

    1907年，科學(xué)家Ernest Rutherford（阿內(nèi)斯特 羅斯福）,證實阿爾法衰變的粒子是氦的原子核。

    氦的主要用途是替代氫，用在氣球中，因為氫太容易燃燒了。很多人知道的用途是給集會氣球充氣，其它的用途是用于焊接（這種用途的氦氣必須要非常純）,氦可以和氫混合用于激光。

    恒星中都有氦，氦參與原子核聚變反應(yīng)，形成整個宇宙中所有的其它元素。