What is the half-life of a radioisotope if a 20 g sample becomes 5 g after 2 days?

What is the ima of the 1 st class lever in the graphic given? 2 3 0.5

Rocks, as they are compressed, begin forming mountains above the earth's surface when two continental plates converge. the continental crust increases in depth as the mountains grow above. the himalayan mountains formed at a convergent plate boundary in this manner. the rocks are smashed together causing them to due to the intense heat and pressure from the colliding plates and eventually forming rock. a) melt; igneous b) layer; sedimentary c) recrystallize; metamorphic d) melt into the earth's interior; metamorphic

How is the atomic number of a nucleus changed by alpha decay