Correct Answer - Option 2 : 35.5 u
The correct answer is 35.5 u.
- The isotopes of chlorine, found in nature are in the ratio 3 : 1.
Average atomic mass of chlorine
= (35 x 75/100) + (37 x 25/100)
= 105/4 + 37/4
= 142/4
= 35.5 u
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The average atomic mass of chlorine is equal to 35.5 u.
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The average atomic mass is the weighted average of the atomic masses of the naturally occurring isotopes of an element.
- To find the average atomic mass of an atom, we take into account all of the isotopes that exist and the percentage of each type.
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Average atomic mass = (Mass of isotope × Relative abundance).
- The atomic number of an atom is equal to the number of protons in the nucleus of an atom or the number of electrons in an electrically neutral atom.
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Atomic number = Number of protons.
- It is represented with the letter ‘Z'.
- The mass number is defined as the sum of the numbers of protons and neutrons present in the nucleus of an atom.
- It is represented using the letter ‘A'.
- Elements with the same atomic number but a different mass number are defined as Isotopes.
- The mass number is commonly cited in distinguishing among the isotopes of an element.
- The atomic mass of an element can be described as the total mass of one atom of the given element.
- Its unit is called the unified atomic mass unit and is denoted by the symbol ‘u’.
