6 Na + F2 ---> 2 Na3F What is the molar mass of sodium fluoride as it is shown in the equation?
O 79.984 g/mol
175.936 g/mol
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137.94 g/mol
087.868 g/mol

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.