Helium ground state electronic configuration, 18 19

A neutral helium atom has two electrons. To write the ground-state electron configuration of He, we apply the aufbau principle. One unique set of quantum numbers is assigned to each electron, moving from the most stable orbital upward until all electrons have been assigned. The most stable orbital is always ly( = l,/ = 0, JW/ = 0 ). 

Refer to the sets of quantum numbers for hydrogen and helium that you saw earlier. Then use the quantum numbers for lithium to infer why a lithium atom has the ground state electron configuration that it does. 

The ground state electronic configuration of helium, 2He, completely fills the 1 s-orbital with two electrons. The spins of the electrons are paired. The configuration for helium would be read as one-s-two (not one-s-squared). 

Each element Ne, Ar and Kr has a ground state electronic configuration. ..ns np. Helium is the odd one out, but still possesses a filled quantum level this is a characteristic property of a noble gas. 

It can now be seen that there is a direct and simple correspondence between this description of electronic structure and the form of the periodic table. Hydrogen, with 1 proton and 1 electron, is the first element, and, in the ground state (i.e. the state of lowest energy) it has the electronic configuration ls with zero orbital angular momentum. Helium, 2 = 2, has the configuration Is, and this completes the first period since no... 

Fig. 13.4 Logarithm of error(Eh) in the configuration interaction energy for the ground state of the helium atom as a function of maximum orbital quantum number, L, of the one-electron basis functions. The data were obtained in an...

Exercise 6-1 Write the ground-state configuration for a helium atom with two unpaired electrons (He ) that is in accord with the Pauli principle. Give your reasoning. 

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