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When we delve into the reasons behind the buoyant behavior of balloons, Archimedes' principle is fundamental. Imagine an object submerged in a fluid; it could be a boat in water or a balloon in air. According to this principle, the fluid exerts an upward force on the object, known as the buoyant force. This force is not random but specifically equal to the weight of the fluid displaced by the object.

For a balloon in the air, Archimedes' principle applies as the air is also considered a fluid. If the balloon’s overall density, considering both the material of the balloon and the gas inside, is less than that of the air, it will displace a volume of air that weighs more than the balloon itself. Consequently, the balloon experiences a net upward, or buoyant, force, allowing it to rise.

Buoyancy is essentially an object's ability to float in a fluid (liquid or gas). This concept is tightly intertwined with Archimedes' principle. The buoyant force acting upon an object is what dictates whether it will sink, float, or remain suspended in the fluid.

In the context of a helium balloon, buoyancy explains why it floats upward. The balloon, when filled with helium, is less dense than the surrounding air. As a result, it floats due to the buoyant force being greater than the gravitational force pulling it down. Put simply, buoyancy is what makes a child's helium balloon escape towards the sky when released outdoors.

When it comes to making things float in the air, lighter-than-air gases like helium are chosen for balloons. Helium is particularly favored because it is significantly less dense than the air around us. As we've learned from the principles of buoyancy, a low-density gas causes the balloon to float as it displaces a heavier air mass.

Furthermore, helium is inert, meaning it is non-reactive and safe to use in environments with humans, adding to its popularity for balloons. It not only provides the desired buoyant characteristic but also offers a measure of safety over other lighter gases like hydrogen, which is highly flammable.

Understanding gas laws helps us further comprehend why a balloon floats when filled with helium. Gas laws are physical laws that describe the behavior of gases, including their relationships among temperature, pressure, volume, and amount.

Boyle’s Law and Charles’s Law are particularly important as they explain how gases like helium will expand and contract with changes in pressure and temperature, affecting the density of the gas. Helium, when heated, will expand and occupy more volume than air at the same temperature and pressure, further decreasing its density and contributing to the lifting power of the balloon.