Bohr radius (first orbit scale) (a0 ≈ 52.9 pm (0.529 Å))

jee-advancedjee-mainneet-ug

a0 ≈ 52.9 pm (0.529 Å)

What each symbol means

SymbolWhat it stands for
eElementary charge
a_0Bohr radius — radius of first Bohr orbit for hydrogen (m or pm)
m_eElectron mass
\hbarReduced Planck constant
\varepsilon_0Vacuum permittivity

When to use this

Defines the natural length scale for hydrogenic atoms in the Bohr model; numerical value is for infinite nuclear mass approximation.