An atom of boron (atomic number 5) contains five electrons. The n = 1 shell is filled with two electrons and three electrons will occupy the n = 2 shell. Because any s subshell can contain only two electrons, the fifth electron must occupy the next energy level, which will be a 2p orbital.

scandium

Boron is the fifth element with a total of 5 electrons. In writing the electron configuration for Boron the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for B goes in the 2s orbital. The remaining electron will go in the 2p orbital.

The third period is similar to the second, except the 3s and 3p sublevels are being filled. Because the 3d sublevel does not fill until after the 4s sublevel, the fourth period contains 18 elements, due to the 10 additional electrons that can be accommodated by the 3d orbitals.

Explanation: According to (n+l) rule: Orbital which has the least value of (n+l) will be filled first to the electrons. Example: 3s orbital will be filled first and then 3p orbital. Orbital.

principal quantum number

(a) Bohr Bury Rules: (i) The maximum number of electrons present in a shell is given by the formula 2n2 (where n is shell no.) (ii) The maximum number of electrons that can be accommodated in the outer most orbit is 8. (iii) Electron are not accommodated in a given shell, unless the inner shells are filled.

i. The maximum number of electrons that could be present in a shell is given by the rule 2n2, where n is the orbit number or energy level. Example, in first shell, n=1, then number of electrons = 2.

In 1913, Niels Bohr proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, but only in prescribed orbits, and If electrons jump to a lower-energy orbit, the difference is sent out as radiation.

Atomic model The Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons. Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element.

The Bohr model is important because it was the first model to postulate the quantization of electron orbits in atoms. Thus, it represents an early quantum theory that gave a start to developing modern quantum theory. It introduced the concept of a quantum number to describe atomic states.

The gold foil experiment showed that the atom has a positively charged nucleus which holds most of its mass. It was the basis for the nulear model of the atom.

Gold was used because it was the only metal that could be rolled out to be very, very thin without cracking. Since the gold foil was very thin, it was thought that the alpha particles could pass straight through it, or possibly puncture the foil. most of the alpha particles did pass straight through the foil.