Cesium-137 has a half-life of 30 years. If a 40 g sample decays over a period of 90 years, how many grams of cesium-137 would remain?

Which best describes how johannes kepler developed his laws of planetary motion

What material does not melt at any temperature

According to the valence shell electron pair repulsion (vsepr) theory, a molecule that has four electron groups around the central atom will exhibit what electron geometry? view available hint(s) according to the valence shell electron pair repulsion (vsepr) theory, a molecule that has four electron groups around the central atom will exhibit what electron geometry? trigonal bipyramidal tetrahedral square planar determination of electron geometry requires information on whether the electron groups are lone pairs or bonding groups.