The correct answers are: -orbits of electrons, -quantum energy emissions and -relationship between outer shell and chemical properties
Neil Bohr was the first who explained that electrons moves around the nucleus in the separate orbits or shells in an atom. The properties of an element is determined by the number of electrons in outer shell. He also discovered that electrons can only be in a particular orbits of fixed energy and when electrons allowed to jump from one orbit to another, they absorbed or emitted electromagnetic radiation.
Answer:
1.orbits of electrons.
3.quantum energy emissions.
