A scientist is studying a radioactive element that has a half-life of 63 years. Choose the correct answers from the drop-down menus to complete each statement about the element. It will take
years for half of the sample to decay.

In 189 years,
of the sample will be left.

Scientists can figure out how old a sample is by multiplying the
by the length of the half-life.

the molecules move in straight line until they collide with each other or with the walls of the container. collisions are perfectly elastic; when two molecules collide, they change their directions and kinetic energies, but the total kinetic energy is conserved.

explanation:

i think slash and

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)