英语翻译麻 烦 帮 忙 翻 译 这 句 话,分 析 语 法 it is helpful to imagine a met

想象一个由没有带负电的价电子环绕的正电性原子核所构成的金属晶体（对理解前文提到的某种理论）是有帮助的.
it is helpful to （形式主语）
imagine a metal crystal
（crystal的后置定语）composed of positive ion cores atoms
without their valence electron（atoms的后置定语）,
about which the negative electrons circulate.（定语从句）

it is helpful to imagine a metal crystal composed of positive ion cores atoms without their valence electron, about which the negative electrons circulate.
it是形式主语
真正的主语是 to imagine a metal cr...