isotopes quiz

📚 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. The mass number ($A$) is the sum of protons ($Z$) and neutrons ($N$): $A = Z + N$.
• 🧪 Isotopes are often represented as $^A_ZX$, where $X$ is the element symbol, $A$ is the mass number, and $Z$ is the atomic number (number of protons). For example, Carbon-14 is $^{14}_6C$.
• ☢️ Some isotopes are stable, while others are radioactive, meaning they decay over time. Radioactive isotopes are used in various applications, including carbon dating and medical imaging.
• ⏳ Half-life ($t_{1/2}$) is the time it takes for half of the radioactive isotopes in a sample to decay.
• ⚗️ The average atomic mass of an element is a weighted average of the masses of its isotopes, taking into account their natural abundances.
• 💡 Formula for average atomic mass: $\text{Average Atomic Mass} = \sum (\text{Isotope Mass} \times \text{Relative Abundance})$

🧪 Practice Quiz

1. Which of the following defines isotopes?
   1. Atoms with the same number of neutrons but different numbers of protons.
   2. Atoms with the same number of protons but different numbers of neutrons.
   3. Atoms with different numbers of protons and electrons.
   4. Atoms with the same mass number but different atomic numbers.
2. What is the mass number of an isotope?
   1. The number of protons in the nucleus.
   2. The number of neutrons in the nucleus.
   3. The sum of protons and electrons in the atom.
   4. The sum of protons and neutrons in the nucleus.
3. Which notation correctly represents an isotope of Carbon with 6 protons and 8 neutrons?
   1. $^{12}_6C$
   2. $^{14}_6C$
   3. $^{14}_8C$
   4. $^{6}_{14}C$
4. What is the term for isotopes that spontaneously decay?
   1. Stable isotopes
   2. Radioactive isotopes
   3. Neutral isotopes
   4. Ionic isotopes
5. What does 'half-life' refer to?
   1. The time it takes for all radioactive isotopes to decay.
   2. The time it takes for half of the radioactive isotopes to decay.
   3. The time it takes for a single radioactive isotope to decay.
   4. The time it takes for radioactive isotopes to become stable.
6. An element has two isotopes: Isotope 1 has a mass of 10 amu and a relative abundance of 20%, and Isotope 2 has a mass of 12 amu and a relative abundance of 80%. What is the average atomic mass of this element?
   1. 10.5 amu
   2. 11.6 amu
   3. 11.0 amu
   4. 12.5 amu
7. Which of the following is NOT a characteristic of isotopes of the same element?
   1. Same number of protons.
   2. Same chemical properties.
   3. Different number of neutrons.
   4. Same mass number.