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This question is about atoms and isotopes - AQA - GCSE Chemistry - Question 4 - 2015 - Paper 2

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This question is about atoms and isotopes. (a) Atoms contain protons, neutrons and electrons. A lithium atom has the symbol \( ^3_ 6 Li \). Explain, in terms of su... show full transcript

Worked Solution & Example Answer:This question is about atoms and isotopes - AQA - GCSE Chemistry - Question 4 - 2015 - Paper 2

Step 1

Explain, in terms of sub-atomic particles, why the mass number of this lithium atom is 7.

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Answer

The mass number of lithium is 7 because it is the total of protons and neutrons in the nucleus. A lithium atom has 3 protons and 4 neutrons. Therefore, the mass number can be calculated as:

extMassNumber=extNumberofProtons+extNumberofNeutrons=3+4=7 ext{Mass Number} = ext{Number of Protons} + ext{Number of Neutrons} = 3 + 4 = 7

This shows that the lithium atom has 7 nucleons (protons and neutrons combined), which defines its mass number.

Step 2

Complete the sentences.

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Answer

One mole of a substance is the relative formula mass in grams.

The relative atomic mass of an element compares the mass of an atom of an element with the mass of an atom of carbon-12.

Step 3

Describe the similarities and differences between the isotopes \( ^{18}_8O \) and \( ^{16}_8O \).

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Both isotopes ( ^{18}_8O ) and ( ^{16}_8O ) have 8 protons, which makes them the same element, oxygen. However, they differ in their number of neutrons.

  • ( ^{18}_8O ) has 10 neutrons.
  • ( ^{16}_8O ) has 8 neutrons.

Thus, ( ^{18}_8O ) has a greater mass due to the additional neutrons.

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