Students are trying to identify an element that has many of the same physical and chemical properties as sodium (Na) but a larger atomic mass. Which of the following elements could the students be investigating?

the index of refraction of the second medium is higher. i just took the test trust me !

the correct answer is 2 and 4

answer: 20 percent

the fish culture has become a developing commercial practice in developing countries which is already prominent in developed countries of the world. the major fish protein demand is being supplemented in developing countries is   fishing to meet the needs of the growing population. therefore, in some developing nations, the percentage of animal protein from fish in the diet can be as high as 20 percent.