What element in period 4 is a gas at 0 degrees celsius and 1 atmosphere?

I think the answer is Krypton, since it's the only gas I know in period 4. *Bromine is a liquid*

Firstly, the water in the dams hold gravitational potential energy as they are above ground level. the gravitational potential energy is then transferred to kinetic energy as it falls, spinning the turbinethe turbine then spins the generator, which is a large magnet surrounded by metal coils. by doing this, the generator generates electricity. in this action, the energy transfer taken place is kinetic to electric energy

What’s the solution?