Which element would be expected to have chemical and physical properties closest to those of rubidium?

Rubidium is an element that belongs to Group 1.  As such it will have physical properties similar to the other Group 1 elements.  Rubidium is below Potassium in the periodic table but above Cesium.  As such it would be most like one of those two elements.

A) the enthralling of formation for pure element in its standard state is always positivehope this : )

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