How to plot 1/sqrt(x^2+y^2+z^2) in mathematica?

Hi.
I want to plot 1/sqrt(x^2+y^2+z^2) in Mathematica ver10.0.

Could anybody tell me how to plot 1/sqrt(x^2+y^2+z^2)?

What are the possible ways of visualizing a 4D function in Mathematica?

Is there something like DensityPlot3D to visualize atomic orbitals?

ContourPlot3D