Thank you girls. It is not safe to go in the house because there is radon inside.
Radon is a gas that is colorless, tasteless, and odorless, but also poisonous. It's radioactive, but doesn't react with other elements because it already has 8 valence electrons. It is released by radium and is the heaviest gas known.
Here is radon on the periodic table, with it's atomic mass of 222 and atomic number of 86, in family 18 and period 6.
Radon was ounce used din hospitals to treat cancer, which is ironic because it is the second leading cause of lung cancer lung cancer, after smoking. Some scientific studies have indicated that kids may be more sensitive to radon and it's effects on the human body. Be careful of radon, everyone.