Define (i) atomic number, (ii) mass number - Leaving Cert Chemistry - Question 11 - 2019
Question 11
Define (i) atomic number, (ii) mass number.
Consider an atom of magnesium,
$$^{25}_{12}Mg$$.
(iii) State the atomic number of magnesium.
(iv) How many neutrons has... show full transcript
Worked Solution & Example Answer:Define (i) atomic number, (ii) mass number - Leaving Cert Chemistry - Question 11 - 2019
Step 1
Define (i) atomic number
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Answer
The atomic number is defined as the number of protons in the nucleus of an atom of an element. It also indicates the number of electrons in a neutral atom, establishing the element's identity.
Step 2
Define (ii) mass number
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Answer
The mass number is the total number of protons and neutrons in the nucleus of an atom. It reflects the atom's mass relative to the isotopes of that element.
Step 3
(iii) State the atomic number of magnesium
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Answer
The atomic number of magnesium is 12.
Step 4
(iv) How many neutrons has an atom of $$^{25}_{12}Mg$$?
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Answer
An atom of 1225Mg contains 13 neutrons. This is calculated by subtracting the atomic number from the mass number:
25−12=13.
Step 5
(v) What term is used to refer to atoms of the same element with different numbers of neutrons?
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The term used for atoms of the same element with different numbers of neutrons is 'isotopes'.
Step 6
(vi) How many electrons are present in every neutral magnesium atom?
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Answer
Every neutral magnesium atom has 12 electrons, which corresponds to its atomic number, ensuring that the atom remains electrically neutral.
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