What value do you estimate for zeff experienced by the outermost electron in both na and k by assuming core electrons contribute 1.00 and valence electrons contribute 0.00 to the screening constant?

We know that both Sodium atom (Na) and Potassium atom (K) are alkali metal. They are called as alkali metal due to the ability to form an alkali or a base namely NaOH and KOH of these metals. If we assume that all inner electrons shield to the same degree, then any alkali metal will have a Zeff of +1. 

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.