Question

she is ( ) newer comer to ( )cemistry but she has already made some important discoveries.

这两空填a the 或者不填。 解释下，谢谢！

Answer 1

she is (a ) newer comer to (不填)chemistry是这样吧 but she has already made some important discoveries.
newcomer是个可数名词,而且是第一次出现,前面应该是不定冠词a，类似于I am a teacher.而chemistry是表示学科的名词，前面不需要加任何冠词，例如:He is good at physics.
其他参考：
new comer是可数名词的单数形式，前面必须有限定词(冠词、物主代词、指示代词或不定代词等)；chemistry是不可数名词，前面不用限定词。

Answer 2

a一个新人,the因为是具体的领域

Answer 3

a,不填