Question

What is the ionisation energy of Helium?

Answer 1

1. The ionisation energy of any atom is defined as the amount of energy required to remove an electron from an isolated atom.
2. In ground state of Helium $\left(\mathrm{He}\right)$ has two electron in its $1\mathrm{s}$ orbital.
3. When we remove an electron from Helium it forms Helium ion${\left(\mathrm{He}\right)}^{+}$which resemble Hydrogen atom but have two units of charge in its nucleus.
4. When we calculate the energy to remove remaining electrons from Helium ion it becomes $4\times \left(-13.6eV\right)=54.4eV$.
5. The second energy of Ionisation of Helium ion is $54.4\mathrm{eV}$.