Determining Atomic Mass: Sulphur and Sodium Examples

🧪 Quick Study Guide

• ⚛️ Atomic mass is the mass of an atom, usually expressed in atomic mass units (amu).
• 🧮 It's approximately equal to the number of protons plus the number of neutrons in the nucleus.
• 📊 For elements with multiple isotopes, the atomic mass is the weighted average of the masses of the isotopes.
• ➗ Weighted average is calculated using the formula: $\sum (isotope\ mass \times relative\ abundance)$
• 🔍 Relative abundance is the percentage of each isotope found in nature.
• 📝 The atomic mass is typically found on the periodic table.

Practice Quiz

1. What is the most common isotope of Sulphur?
   1. Sulphur-30
   2. Sulphur-32
   3. Sulphur-34
   4. Sulphur-36
2. What is the approximate atomic mass of Sodium (Na) according to the periodic table?
   1. 11 amu
   2. 22 amu
   3. 23 amu
   4. 24 amu
3. Sulphur has four stable isotopes: $^{32}S$ (94.99%), $^{33}S$ (0.75%), $^{34}S$ (4.25%), and $^{36}S$ (0.01%). Which isotope contributes the most to Sulphur's atomic mass?
   1. $^{32}S$
   2. $^{33}S$
   3. $^{34}S$
   4. $^{36}S$
4. If an element has two isotopes, one with a mass of 10 amu and a relative abundance of 20%, and another with a mass of 12 amu and a relative abundance of 80%, what is the average atomic mass of the element?
   1. 10.5 amu
   2. 11.0 amu
   3. 11.6 amu
   4. 12.2 amu
5. Which of the following statements about atomic mass is correct?
   1. Atomic mass is the same as mass number.
   2. Atomic mass is the number of protons in an atom.
   3. Atomic mass is the weighted average of the masses of an element's isotopes.
   4. Atomic mass is always a whole number.
6. What information is needed to calculate the weighted average atomic mass of an element?
   1. The number of protons and neutrons only.
   2. The mass of each isotope and its relative abundance.
   3. The number of electrons and protons only.
   4. The mass of the most common isotope only.
7. What is the main difference between atomic mass and mass number?
   1. Atomic mass is a weighted average, while mass number is the total number of protons and neutrons.
   2. Atomic mass is always a whole number, while mass number is not.
   3. Atomic mass refers to a single isotope, while mass number refers to all isotopes.
   4. There is no difference between atomic mass and mass number.