I'm thinking of adding some arsenic to the pot of spaghetti that I made for dinner.
Well that's not safe. Why would you add arsenic to the pot of spaghetti?
I'm sick of my family and I want to get rid of them.
Adding a poison to food you're going to serve your family is unethical and wrong. If you're unhappy with your family, then you should get some distance from them. Murdering your family is not the answer to your difficulties with your family.
It's fine, I'm doing it to teach them a lesson.
You really shouldn't go through with this plan. Not only will they all suffer a painful death, but you'll also spend the rest of your life in prison.