Isotopes Explained: Definition, Properties, and Examples

📚 Quick Study Guide

• ⚛️ Isotopes are variants of a chemical element which have the same number of protons and electrons, and therefore the same chemical properties, but different numbers of neutrons.
• ⚖️ Because isotopes of an element have different numbers of neutrons, they have different mass numbers ($A$), which is the total number of protons ($Z$) and neutrons ($N$) in an atomic nucleus: $A = Z + N$.
• ☢️ Some isotopes are stable, while others are radioactive, meaning they decay over time, emitting particles and energy.
• 🧪 Radioactive isotopes have a characteristic half-life ($t_{1/2}$), which is the time it takes for half of the atoms in a sample to decay.
• 📅 Isotopes have a wide range of applications, including carbon dating, medical imaging, and nuclear energy.

🧪 Practice Quiz

1. What defines isotopes of the same element?
   1. Same number of neutrons, different number of protons
   2. Same number of protons, different number of electrons
   3. Same number of protons, different number of neutrons
   4. Same mass number, different atomic number
2. Which of the following is true about the mass number (A) of an isotope?
   1. A = number of neutrons - number of protons
   2. A = number of protons + number of electrons
   3. A = number of protons + number of neutrons
   4. A = number of electrons - number of neutrons
3. What makes an isotope radioactive?
   1. Having too few neutrons
   2. Having an unstable nucleus that decays over time
   3. Having too many protons
   4. Having a very small atomic mass
4. What is half-life ($t_{1/2}$)?
   1. The time it takes for all atoms in a sample to decay
   2. The time it takes for half of the atoms in a sample to decay
   3. The time it takes for an atom to gain stability
   4. The time it takes for an atom to double in size
5. Which of the following is NOT a common application of isotopes?
   1. Carbon dating
   2. Medical imaging
   3. Nuclear energy
   4. Photosynthesis
6. If an isotope has 6 protons and 8 neutrons, what is its mass number?
   1. 6
   2. 8
   3. 14
   4. 2
7. Which statement is correct about isotopes of hydrogen?
   1. They all have the same number of neutrons.
   2. They all have different chemical properties.
   3. They all have one proton but different numbers of neutrons.
   4. They all are radioactive.