The atomic structure of atoms Q, R, S and T are shown in the table.
| Atom | Number of protons | Number of neutrons | Number of electrons |
| Q | 6 | 7 | 6 |
| R | 7 | 7 | 7 |
| S | 6 | 8 | 6 |
| T | 8 | 8 | 8 |
Which two atoms are isotopes?
| A | Q and S |
| B | Q and T |
| C | R and T |
| D | R and S |
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Two isotopes of chlorine are 35Cl and 37Cl.
Using these isotopes, how many different relative molecular masses are possible for the compound with molecular formula C2H3Cl3?
2
3
4
5
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Which row correctly describes the number of outer shell electrons and properties of isotopes?
| Â | Number of electrons | Chemical properties |
| A | same | same |
| B | same | different |
| C | different | same |
| D | different | different |
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1 markIridium has two isotopes, 191Ir and 193Ir. Calculate the relative atomic mass of iridium using the data given:
| Mass number | 191 | 193 |
| Percentage abundance | 62.7% | 37.3% |
191.2
191.6
191.7
192.5
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