The distance from earth to the moon is 384400 kilometers what is this distance expressed in scientific notation

Scientic notation 3.844 x 10^5

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom

Density and pressure