How many moles of
salt (NaCl) is 28.7
grams?

0.491 mol NaCl

Explanation:

Convert from grams to moles using the molar mass of NaCl:

28.7 g NaCl x 1 mol NaCl/58.44 g NaCl = 0.491 mol NaCl

The molar mass (58.44 g) can be found from adding the molar masses of the individual elements (Na and Cl); the g NaCl will cancel out (dimensional analysis), leaving you with mol NaCl.

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

first one is the correct answer