Answer:
Krypton
Explanation:
When Selenium forms an ion, it is trying to become krypton which is a noble gas.
Selenium belongs to the oxygen group on the periodic table. In this group, the atoms prefers to gain two electrons to complete their octet. When selenium gains two electrons, its octet is complete.
This will make the atom resemble krypton on the periodic table of elements.
This structure which is an octet confers a special stability on the element.
The grams of NaCl that are required to make 150.0 ml of a 5.000 M solution is 43.875 g
calculation
Step 1:calculate the number of moles
moles = molarity x volume in L
volume = 150 ml / 1000 = 0.15 L
= 0.15 L x 5.000 M = 0.75 moles
Step 2: calculate mass
mass = moles x molar mass
molar mass of NaCl = 23 + 35.5 = 58.5 mol /L
mass is therefore =0.75 moles x 58.5 mol /l =43.875 g
