Potassium has an atomic number of 19.
which of a potassium atom's electrons are its valence electrons?
select one:
a. those in the third shell from the nucleus.
b. those in the second shell from the nucleus.
c. those in the outermost shell.
d. those in the innermost shell.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.