Atoms, Elements, Molecules, and Compounds

Introduction to Matter

• Definition of Matter: Anything that has mass and volume.
• Examples: Air, water, clothes, books, and homes are all made up of matter.
• Types of Matter: Distinct types of matter are categorized based on the type of atoms they contain.

Elements

• Definition: Distinct types of matter made up of only one type of atom.
• Total Number of Elements: 118 known elements listed in the periodic table.
• Examples of Elements:
  • Oxygen (O)
  • Nitrogen (N)
  • Copper (Cu)
  • Gold (Au)
• Characteristics:
  • Each element has a unique symbol (e.g., Ca for calcium).
  • All atoms in an element are of the same type.

Atoms

• Definition: The smallest unit of an element.
• Structure: Consists of a nucleus, which includes protons and neutrons.

Molecules

• Definition: Composed of two or more atoms bonded together.
• Example of Molecules:
  • Oxygen (O2): Consists of two bonded oxygen atoms.
  • Water (H2O): Composed of two hydrogen atoms and one oxygen atom.
• Key Point: Molecules cannot be broken down into simpler substances by ordinary chemical means.

Compounds

• Definition: Substances consisting of atoms of different elements in a fixed ratio.
• Examples of Compounds:
  • Water (H2O): Two hydrogen atoms and one oxygen atom.
  • Carbon Dioxide (CO2): One carbon atom and two oxygen atoms.
• Characteristics:
  • Compounds are not elements because they contain more than one type of atom.
  • Each compound has a unique chemical formula (e.g., H2O, CO2).

Comparison of Elements and Compounds

• Elements:
  • Composed of only one type of atom.
  • Retain the properties of that element.
• Compounds:
  • Composed of two or more types of atoms.
  • Possess properties that differ from those of the individual elements.
• Breaking Down Compounds:
  • Breaking down compounds results in individual elements, which do not exhibit the properties of the compound.

More Examples

• Elements:

  • Hydrogen (H2)
  • Nitrogen (N2)
  • Oxygen (O2)
  • Chlorine (Cl2)

• Compounds:

  • Nitrogen Oxide (NO)
  • Nitrogen Dioxide (NO2)
  • Carbonic Acid, Sodium Chloride, Hydrochloric Acid, Sulfuric Acid, Calcium Carbonate

Recap

• Matter: Occupies space and has mass.
• Elements: Single type of atom; represented in the periodic table.
• Molecules: Two or more atoms; can be the same or different.
• Compounds: Two or more different types of atoms in fixed ratios; have distinct properties.