Gamma rays are uncharged, high-energy photons. Because they have no electric charge, they don’t interact with matter by electric forces the way charged particles do, so they pass through many materials with little attenuation. Their energy is removed mainly through photon-matter interactions—photoelectric effect, Compton scattering, and, at higher energies, pair production—which depend on the material’s density and atomic number. Dense shielding like lead or concrete increases the likelihood of these interactions and thus reduces the gamma-ray beam. That’s why gamma radiation requires thick, dense shielding. The other ideas—gamma rays carrying charge and interacting strongly, being slowed by magnetic fields, or deflected easily in air—don’t fit because gamma rays have no charge, magnetic fields don’t slow them, and they’re not easily deflected in air.

The main idea is understanding what BE stands for in the formal charge formula. BE means bonding electrons—the electrons that participate in covalent bonds and are shared between atoms. In the formal charge calculation, you count half of BE because each bond is shared, so each atom effectively owns one of the two electrons in that bond. For a single covalent bond, BE is 2 electrons, and you assign 1 electron to each atom’s bond count. Ionic bonds don’t involve sharing electrons, so they don’t contribute to BE in this context. That’s why BE specifically refers to electrons shared in covalent bonds, not bond energy or electrons shared in ionic bonds.

When two aqueous solutions react to form a solid, the net ionic equation keeps only the ions that actually form the precipitate and removes the spectator ions that don’t participate in the solid formation. Here, BaCl2 provides Ba2+ and Cl−, while Na2SO4 provides Na+ and SO4^2−. The sulfate ion and the barium ion combine to make BaSO4, which is insoluble and precipitates. The sodium and chloride ions remain in solution and do not take part in the solid formation, so they’re removed in the net ionic form. Thus the net ionic equation is Ba2+ + SO4^2− → BaSO4(s).

The main idea here is how lone pairs influence molecular shape in VSEPR theory. With four electron domains around the central atom, the electron-domain geometry is tetrahedral, but two of those domains are lone pairs. The two bonding pairs occupy positions that minimize repulsion, resulting in a bent (angular) molecular geometry. The presence of lone pairs pushes the bonds closer together, lowering the bond angle from the tetrahedral 109.5° to about 104.5°, a pattern seen in water. The other shapes correspond to different counts of bonding vs lone pairs: two bonds with no lone pairs would be linear (180°), three bonds with no lone pairs would be trigonal planar (120°), and four bonds with no lone pairs would be tetrahedral (109.5°).