Question

According to Bohr's model. The radius of the second orbit of helium atom is:
A.0.53 ${A^o}$
B.1.06${A^o}$
C.2.120 ${A^o}$
D.0.265${A^o}$

Answer 1

An atom of the chemical element helium is known as a helium atom. The electromagnetic force binds two electrons to a nucleus of two protons and one or two neutrons, depending on the isotope, which is kept together by the strong force.

Formula used:
$r = \dfrac{{{n^2}}}{Z} \times 0.529\;{\text{A}}$

Complete answer: In terms of electron structure, the He ion is identical to the 2 Hydrogen atoms. The radius of the second orbit of the Helium atom can be calculated using the formula for radius given by Bohr's model of the Hydrogen atom. The Helium atomic number and the second orbit's principal quantum number must be identified.
Postulates of Bohr's Model of atom:
Electrons (negatively charged) in an atom orbit or shell around the positively charged nucleus in a definite circular direction.
These circular orbits are known as orbital shells because each orbit or shell has a fixed energy.
The quantum number is an integer (n=1, 2, 3,...) that represents the energy levels. This quantum number spectrum begins on the nucleus's side, with n=1 having the lowest energy density. K, L, M, N.... shells are assigned to the orbits n=1, 2, 3, 4..., and an electron is assumed to be in the ground state as it reaches the lowest energy stage.
Formula used:
$r = \dfrac{{{n^2}}}{Z} \times 0.529\;{\text{A}}$
For radius of the second orbit of helium atom,
n=2
Z=2
${\text{r}} = \dfrac{{{2^2}}}{2} \times 0.529 = 2 \times 0.529 = 1.058\mathop {{{\text{A}}^o}}\limits^. \approx 1.06\;{{\text{A}}^o}$
As a result, according to Bohr's model, the radius of the helium atom's second orbit is 1.06${A^o}$

Note:
The Bohr model is a description of the structure of atoms, especially hydrogen, proposed by Danish physicist Niels Bohr in 1913. The Bohr model of the atom was the first to introduce quantum theory and was the forerunner of wholly quantum-mechanical models. It was a fundamental departure from older, classical definitions. The properties of atomic electrons are defined by the Bohr model and all of its descendants in terms of a set of permitted (possible) values. Only when electrons suddenly leap between permitted, or stationary, states do atoms absorb or emit radiation.