Hello!
Yes, I totally believe that you can achieve that 99 ATAR if you work hard, are persistent despite bad marks and work consistently throughout the year.
You've only had one sac for chemistry and there are still 4 more to go! So, you can still climb up the rankings and redeem yourself and of course, there's the exam.
It's important for you to not only recognise that you have terrible work habits but you also need to ask yourself: how am I going to fix this and transform them into amazing work habits? If you really really really want to achieve that 99 ATAR, you will need to tell yourself that 'I'm going to be disciplined' and 'I'm going to become more consistent with my studies.' What I keep telling myself is 'this is your last year, if you don't do everything you can this year, then there's no going back'.
Keep at it and all the best for your studies!
EDIT: Oops, Bri MT beat me to it but I'll keep this here anyways.