Final answer:
A gas deviates most from the ideal gas law at low temperatures and high pressures due to the increased significance of molecule volume and intermolecular attractions.
Step-by-step explanation:
A gas will be least likely to exhibit the ideal gas properties predicted by the ideal gas law under conditions of low temperatures and very high pressures. At high pressures, gas molecules are forced closer together, which means they occupy a more significant volume relative to the space they are in, challenging the assumption that their volume is negligible. At low temperatures, the decreased kinetic energy of the gas particles means that intermolecular attractions become more significant, further deviating from ideal behavior.