Being farther from the nucleus and with more electrons shielding the protons results in the valence electrons being held ...

Weakly

Explanation:

Being farther from the nucleus and with more electrons shielding the protons results in the valence electrons being held weakly.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).

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.