Which is the correct chemical symbol for this atom of helium?

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

Acontainer holds 35.8 moles of gas under 10.0 atm of pressure at 70.0 c. what is the volume of the container?

Which of the following is true about the speed of light? it depends on the wavelength.