Quiz on Molecules and Atoms for Middle School

📚 Quick Study Guide

• ⚛️ An atom is the basic building block of matter.
• ➕ Atoms are made of protons (+ charge), neutrons (no charge), and electrons (- charge).
• 🧪 The atomic number tells you how many protons are in an atom.
• 🤝 Molecules are formed when two or more atoms join together chemically.
• 🌊 For example, water ($H_2O$) is a molecule made of two hydrogen atoms and one oxygen atom.
• 🔗 Chemical bonds hold atoms together in molecules.
• 💡 Ions are atoms or molecules that have gained or lost electrons, giving them an electrical charge.

Practice Quiz

1. Which of the following is the smallest unit of matter that retains the chemical properties of an element?
   1. A. Molecule
   2. B. Compound
   3. C. Atom
   4. D. Ion
2. What is the charge of a proton?
   1. A. Negative
   2. B. Neutral
   3. C. Positive
   4. D. Variable
3. Which of the following is a molecule?
   1. A. Na
   2. B. Cl
   3. C. $H_2O$
   4. D. K
4. What is formed when two or more atoms bond together?
   1. A. Ion
   2. B. Molecule
   3. C. Element
   4. D. Isotope
5. What are atoms or molecules with an electrical charge called?
   1. A. Neutrons
   2. B. Protons
   3. C. Ions
   4. D. Electrons
6. Which subatomic particle has a negative charge?
   1. A. Proton
   2. B. Neutron
   3. C. Electron
   4. D. Ion
7. What does the subscript '2' indicate in the molecule $CO_2$?
   1. A. Two carbon atoms
   2. B. Two oxygen atoms
   3. C. The charge of the molecule
   4. D. Two molecules of carbon dioxide