Seh2 molecule -- how many lone-pairs of electrons are on the central se atom? h3o+ ion -- how many lone-pairs of electrons are on the central o atom? seo2 molecule -- how many lone-pairs of electrons are on the central se atom?

Se as in SeH₂: Two lone pairs.

O as in H₃O⁺: One lone pair.

Se is a group 16 element. Both Se and O have six valence electrons in each neutral atom. The structure of an SeH₂ molecule resembles that of a water H₂O molecule. Two Se-H bonds connect the three atoms in each SeH₂ molecule.

Two valence electrons on the central Se atom would go to the two Se-H bonds. The four valence electrons remaining would form two lone pairs.

H₃O⁺ has a trigonal pyramidal geometry.

It takes 2 + 3 × 1 + 1 = 6 extra electrons to ensure an octet for all four atoms in a H₃O⁺ ion. The ion would achieve that configuration by forming 6 / 2 = 3 O-H bonds. The central oxygen atom has six valence electrons when it is neutral. Now it has five in this cation after having lost one to acquire the charge of +1. Three of the valence electrons go to three O-H bonds. The remaining two become a lone pair.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.