Table of contents

1. The Chemical World9m
- The Scientific Method
  9m
2. Measurement and Problem Solving2h 19m
3. Matter and Energy2h 15m
4. Atoms and Elements2h 33m
5. Molecules and Compounds1h 50m
6. Chemical Composition1h 23m
7. Chemical Reactions1h 43m
8. Quantities in Chemical Reactions1h 8m
9. Electrons in Atoms and the Periodic Table2h 32m
10. Chemical Bonding2h 10m
11 Gases2h 7m
12. Liquids, Solids, and Intermolecular Forces1h 11m
13. Solutions3h 1m
14. Acids and Bases2h 14m
15. Chemical Equilibrium1h 27m
16. Oxidation and Reduction1h 33m
17. Radioactivity and Nuclear Chemistry53m

4. Atoms and Elements

Ions (Simplified)

Introduction to Chemistry

4. Atoms and Elements

Ions (Simplified)

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Multiple Choice

In which pair are the two species both isoelectronic and isotopic?

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Understand the terms: Isoelectronic species have the same number of electrons, while isotopic species have the same number of protons but different numbers of neutrons.

Analyze the first pair: \( ^{40}_{20}\text{Ca}^{2+} \) and \( ^{40}_{18}\text{Ar} \). \( \text{Ca}^{2+} \) has 18 electrons (20 protons - 2 charge), and \( \text{Ar} \) has 18 electrons. Both have the same mass number, 40, but different atomic numbers, so they are not isotopic.

Analyze the second pair: \( ^{23}_{11}\text{Na}^{+} \) and \( ^{24}_{11}\text{Na}^{+} \). Both have 10 electrons (11 protons - 1 charge), but different mass numbers, 23 and 24, indicating they are isotopes.

Analyze the third pair: \( ^{24}_{12}\text{Mg}^{2+} \) and \( ^{25}_{12}\text{Mg} \). \( \text{Mg}^{2+} \) has 10 electrons (12 protons - 2 charge), while \( \text{Mg} \) has 12 electrons. They are isotopes but not isoelectronic.

Analyze the fourth pair: \( ^{56}_{26}\text{Fe}^{2+} \) and \( ^{57}_{26}\text{Fe}^{3+} \). \( \text{Fe}^{2+} \) has 24 electrons (26 protons - 2 charge), and \( \text{Fe}^{3+} \) has 23 electrons. They are isotopes but not isoelectronic.