bound atom

基本解释

Methane, four atoms of hydrogen bound to a carbon atom, is the main component of natural gas on Earth.
甲烷由四个氢原子和一个碳原子组成，是构成地球大气的主要气体。
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The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule.
电子原子必将核的电磁力。同样，一组原子可以保持彼此的约束，形成了分子。
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The target atom or ion may be excited to infinite bound states, auto-ionizing states and adjoint continuum states which can be treated in an unified manner by Multichannel Quantum Defect Theory.
电子碰撞过程可将靶原子或离子激发至无数的束缚态、自电离态和对应的连续态，多通道量子数亏损理论能够统一地处理这些激发态。

So it's trigonal because we have these three atoms that are bound to the central atom here, and if you picture it, it's actually shaped like a pyramid.
这里三角形是因为,我们有3个原子核中心原子成键，如果你画它，它就是金字塔形的。
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This is partly explained because the bigger an atom is, the more weakly its outer electrons are bound to it (and hence the further those electrons are from the nucleus).
ECONOMIST: Einstein and car batteries