Answer:
Because isotopes of the same element only differ by a few neutrons. An example is carbon-12 and carbon-14 isotopes which differ by 2 neutrons in their atomic nuclei. 
Explanation:
Isotopes of the same element share the same chemical properties because they bear the same number of electrons (remember electrons are what are involved in chemical reactions). Therefore one can't use chemical methods to separate isotopes. 
Separating isotopes require mechanical separation using ultra-high-speed centrifuges with very high-resolution power such that the little mass difference between the isotopes (due to differences in neutron numbers) can be used to separate them. 
Learn More:
For more on isotopes check out;
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F  atomic number 9, mass 19
Ne  atomic number  10, mass 20
Na  atomic number 11, mass 23
Mg  atomic number 12, mass 24
 
        
             
        
        
        
A total solar eclipse happens when the moon completely hides the solar surface, cutting off all direct rays of sunlight from the the person watching.
 
        
             
        
        
        
Phenolphthalein Phenolphthalein is a universal indicator, which means it changes color to show the pH of certain solutions. Phenolphthalein stays colorless in acidic solutions and turns pink in alkaline solutions. Sodium hydroxide is a base, so when you add phenolphthalein, the solution turns pink. Other indicators commonly used in the laboratory are litmus and methyl orange. A Litmus indicator solution goes red in acidic solutions, blue in alkaline solutions and purple in neutral solutions. Methyl orange turns red in acidic solutions and yellow in neutral or alkaline solutions.
        
             
        
        
        
Impossible to form from given reactants
Explanation:
Only sodium has carbonate ion here .so only possible way to displace carbonate is to use potassium
When sodium carbonate and Potassium iodide react with each other double displacement reaction occurs
As potassium is powerful than sodium it displaces sodium to form potassium carbonate .
Then you have to use water and then you can use calcium suppliment .