Vitamin K antagonists (VKA) are a group of substances that reduce blood clotting by reducing the action of vitamin K. They are used as anticoagulant medications in the prevention of thrombosis, and in pest control, as rodenticides. 1  1 Mechanism of action.  2 Coumarins (4-hydroxycoumarins)
Calculate the average atomic mass of oxygen. Solution: ((15.994915*99.757) + (16.999132*0.038) + (17.999160*0.205))/100 = 15.999405 . Using our equation for determining average atomic mass, we see that the average atomic mass for oxygen is 15.999405 amu. If we check the periodic table, we will see that our average atomic mass is the same as the atomic mass indicated on the element oxygen. Ã
  An oxygen molecule is diatomic ie. it has two atoms (O2). As the atomic mass of a single oxygen atom is indeed 16, the molecular mass of O2 is (2 x 16) = 32.xygen-17 has 9 neutrons and 8 protons. The only difference is the atomic mass due to the different number of neutrons. Number of p â¦ rotons & electrons stay the same. The difference is in the number of neutrons in the nucleus. Oxygen-15 has 7 neutrons, oxygen-16 has 8, and oxygen-17 has 9.