Basic Chemistry Quiz

Basic Chemistry

• Elements are the simplest form of matter, indivisible into simpler substances.
• The periodic table contains 120 known elements, each with a unique symbol (e.g., Au for gold).
• Atoms are the building blocks of elements.
• Atoms consist of:
  • Protons: Positively charged, located in the nucleus.
  • Neutrons: Neutral, located in the nucleus, similar size to protons.
  • Electrons: Negatively charged, orbit the nucleus, much smaller than protons or neutrons.
• Atomic number: The number above the element symbol, representing the number of protons (and in a neutral atom, electrons).
• Atomic mass: The number below the element symbol, representing the total number of protons and neutrons.
• To find the number of neutrons, subtract the atomic number from the atomic mass.
• Ions form when the number of electrons changes, altering the charge of the atom.
• Changing the number of protons changes the element.
• Isotopes form when the number of neutrons changes; they are generally unstable and radioactive.
• Compounds result from two or more elements bonded together.
• Ionic bonds occur when one atom donates an electron to another.
• Covalent bonds occur when atoms share electrons.
• Molecules are the smallest functional units of compounds. For example, H₂O is a single water molecule.
• The pH scale measures the concentration of free hydrogen ions in a solution.
• A pH of 7 is neutral.
• A pH of less than 7 is acidic.
• A pH of greater than 7 is alkaline (basic).
• A change of one whole number on the pH scale represents a ten-fold change in hydrogen ion concentration. A pH of 4 is ten times more acidic than a pH of 5.