Answer: 80
Explanation:
Elements are arranged in periodic table in order of increasing atomic number.
Atomic number is defined as the number of protons or number of electrons that are present in an atom.
Atomic number = Number of electrons = Number of protons
Mercury (Hg) is a d block element and its atomic number is 80, thus it contains 80 protons and 80 electrons.
Electronic configuration represents the total number of electrons that a neutral element contains. We add all the superscripts to know the number of electrons in an atom.
Electronic configuration of mercury in terms of noble gas configuration is [tex][Xe]4f^{14}5d^{10}6s^{2}[/tex].
