A surplus (having “extra”) or deficit (having “fewer”) of electrons?

Rutherford's experiment indicated that matter was not as uniform as it appears what part of his experimental results implied this idea

Ahypothrticalax type of ceramic material is known to have a density of 2.10 g/cm3 and a unit cell of cubic symmetry with a cell edge length of 0.57 nm. the atomic weights of the a and x elements are 28.5and 30.0 g/mol, respectively. on the basis of this information, which of the following crystal structures is (are) possible for this material: sodium chloride, cesium chloride, or zinc blende

Express the following number in scientific notation. 0.026890 =