General Chemistry Notes

1. Matter and Its States

• Solid: Fixed shape and volume
• Liquid: Fixed volume, no fixed shape
• Gas: No fixed shape or volume

2. Atomic Structure

• Atoms consist of protons, neutrons, and electrons
• Protons (+), Neutrons (0), Electrons (−)
• Atomic number = number of protons
• Mass number = protons + neutrons

3. Elements, Compounds, and Mixtures

• Element: Pure substance of one type of atom
• Compound: Two or more elements chemically combined
• Mixture: Two or more substances physically combined

4. Acids, Bases, and Salts

• Acid: Releases H⁺ ions (e.g., HCl)
• Base: Releases OH⁻ ions (e.g., NaOH)
• Salt: Formed from acid + base (e.g., NaCl)

Equation: HCl + NaOH → NaCl + H₂O

5. Periodic Table Groups

Group 1: Alkali Metals

• Very reactive, soft metals
• React with water to form alkalis
• Example: 2Na + 2H₂O → 2NaOH + H₂↑

Group 2: Alkaline Earth Metals

• Moderately reactive