The dot point says to assess its significance to society. Is it enough to know 5 positive impacts and 5 negative impacts? We also learnt a timeline of the main events in class, but is that really necessary to what the syllabus asks for?
it just says "assess". So just pros and cons on the impact on society and the judgement is enough.
historical timeline of events isnt necessary but maybe you are learning it to aid your understanding of the Manhattan project?