Composition of the Atomic Nucleus. Isotopes

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The composition of the atomic nucleus. Isotopes
 
         The mass number of an element is equal to the sum of the number of protons and the number of neutrons in the atomic nucleus:
where - the number of protons, - the number of neutrons.
A type of atoms of the same element with the same atomic number but different masses  isotopes is called For example, isotopes of potassium
isotope has 19 protons, 39 — 19 = 20 neutrons
isotope has 19 protons, 40 — 19 = 21 neutrons
isotope has 19 protons, 41 — 19 = 22 neutrons
Example 1. It consists of a mixture of boron and isotopes. The average atomic mass of boron is 10,82. What percentage of atoms of each isotope are in boron?
Solution: We take the total mass of boron isotopes as 100%. If the percent composition of the isotope is equal to x, it will be equal to 100-x. From this, an algebraic equation expressing the mass balance of atom B in percent is created:
  that is
 10x+1100-11x =1082 of this
 x = 18 .
 So, q18% is equal to 100-18q82%.
Example 2. Natural chlorine is composed of a mixture of 75,4% and 24,6% isotopes. Calculate the average relative atomic mass of chlorine.
Solution: This problem is the reverse of Example 1. Therefore, let's define the average mass of chlorine by x and create an algebraic equation as follows:
35.75,4 + 37.24,6 q 100x ðfrom this
  xq 35,46 amb
So, the average relative atomic mass of chlorine is 35,46 amb.
Problems for independent solution
 
  1. Determine how many protons and how many neutrons are in the nuclei of the following atoms: 1531P; 1941K; 1225Mg; 2040Ca; 3065Zn; 3581Br; 46104Pd; 50122Sn; 56130Ba; 78188PT.
  2. In bromine, which has a relative atomic mass of 79,916 3579Br and 3581Find the percentage of Br isop.
  3. Lithium 36Lee and 37It consists of a mixture of Li and its average relative atomic mass is 6,94. Find the percentage of lithium isotopes.
  4. Silver 47107Ag and 47109It consists of a mixture of Ag and its average relative atomic mass is 107,88. Find the percentage of silver isotopes.
  5. Natural Neon 90% 1020Ne and 10% 1022Ne is composed of a mixture of isotopes. Calculate the average relative atomic mass of neon.
  6. Natural Copper 27% 2965Cu and 73% 2963 Cu is composed of a mixture of isotopes. Calculate the average relative atomic mass of copper.
  7. Magnesium 78,6% 1224Mg and 11,29% 1225Mg is composed of a mixture of isotopes. Calculate the average relative atomic mass of magnesium.
  8. Lives 510B and 511It consists of compound B and its average relative atomic mass is 10,81. H3BO3 acid content  511How many B are there?

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