Define (i) atomic number, (ii) mass number, (iii) isotopes - Leaving Cert Chemistry - Question b - 2018
Question b
Define (i) atomic number, (ii) mass number, (iii) isotopes.
Refer to the periodic table of the elements on page 79 of the Formulae and Tables booklet and answer the... show full transcript
Worked Solution & Example Answer:Define (i) atomic number, (ii) mass number, (iii) isotopes - Leaving Cert Chemistry - Question b - 2018
Step 1
Define (i) atomic number
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Answer
The atomic number is defined as the number of protons in an atom of an element. It gives the element's position in the periodic table and also indicates the number of electrons present in a neutral atom.
Step 2
Define (ii) mass number
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The mass number is the total number of protons and neutrons in an atom of an element. It represents the total mass of the nucleus.
Step 3
Define (iii) isotopes
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Isotopes are atoms of the same element that have the same atomic number but different mass numbers due to varying numbers of neutrons.
Step 4
What is the atomic number of chlorine?
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The atomic number of chlorine is 17.
Step 5
How many electrons occupy each of the main energy levels (shells) in a chlorine atom?
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In a chlorine atom, the electron configuration is 2 electrons in the first shell and 7 electrons in the second shell, thus 2, 7.
Step 6
What is the relative atomic mass of chlorine?
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The relative atomic mass of chlorine is approximately 35.45.
Step 7
Why is the relative atomic mass of chlorine not a whole number?
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The relative atomic mass of chlorine is not a whole number because it is a weighted average of the mass numbers of the isotopes as they occur naturally, which includes isotopes of varying masses.
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