Led reacts vigorously with fluorine at room temperature. Chlorine, which is in the same vertical group as fluorine, react dangerously with lead when heated. Why might these two elements react so much with lead?

Ithink it’s 3 as the answer.

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water