atoms and molecules并列名词作复合主语 always 状语were much（程度修饰的状语） more比较结构的状语 likely to emit light spontaneously状语.
were likely to emit复合结构作状语 light作宾语那谓语呢？我不懂得地方是were likely to emit light的谓语和宾语是怎么划分的？尤其的这里的谓语是有什么成分做的？were likely to emit前面的就是谓语呀，这种叫复合谓语，核心词是动词emit，而 light就是emit的宾语