Classification of Matter, Elements, Compounds, and the Periodic Table

Matter and Measurements

Classification of Matter

Matter is anything that has mass and occupies space. It can be classified based on its composition and physical properties.

• Elements: Pure substances made up of only one type of atom. Cannot be broken down by chemical means.

• Compounds: Substances formed by chemically combining two or more elements in a fixed ratio. Represented by chemical formulas.

• Mixtures: Physical combinations of two or more substances. Can be homogeneous (uniform composition) or heterogeneous (non-uniform composition).

Examples

• Elements: Cu (Copper), Mn (Manganese), Li (Lithium), Br (Bromine), O2 (Oxygen), Cl2 (Chlorine)

• Compounds: CuO2, C6H12O6 (Glucose), SO2 (Sulfur dioxide), NH3 (Ammonia), C3H8 (Propane), LiCl (Lithium chloride)

• Homogeneous Mixtures: Salt water, air, steel

• Heterogeneous Mixtures: Mint chocolate chip ice cream, chicken noodle soup, cereal and milk

Atoms and the Periodic Table

Periodic Table Organization

The periodic table arranges elements by increasing atomic number and groups elements with similar properties into columns.

• Metals: Located on the left side of the periodic table. Good conductors of electricity, malleable, ductile, high melting and boiling points. Tend to form cations via ionic bonding.

• Nonmetals: Located in the upper right of the periodic table. Poor conductors, not malleable or ductile, low melting and boiling points. Tend to form covalent bonds and molecular compounds.

• Noble Gases: Located in column 8A/18. Have 8 valence electrons, typically non-reactive.

Subatomic Particles

• Protons: Positively charged (+1), located in the nucleus. The number of protons defines the atomic number.

• Neutrons: Neutral charge, located in the nucleus. Number can vary (isotopes).

• Electrons: Negatively charged (-1), located outside the nucleus. The group number indicates the number of valence electrons; atomic number matches total electrons in a neutral atom.

Ionic and Molecular Compounds

Ions

• Cations: Positively charged ions formed by losing electrons. Often metals or polyatomic ions like ammonium (NH4+).

• Anions: Negatively charged ions formed by gaining electrons. Often nonmetals or polyatomic ions.

Bonding Types

• Ionic Bonding: Occurs between metals and nonmetals. Involves transfer of electrons from cation to anion.

• Covalent Bonding: Occurs between nonmetals. Involves sharing of electrons.

States of Matter

Solids

• Particles are close together.

• Definite shape and volume.

Liquids

• Particles are close together but can move past each other.

• Definite volume, indefinite shape.

Gases

• Particles are far apart and move freely.

• No definite shape or volume.

Summary Table: Classification of Matter

Type	Description	Examples
Element	Pure substance, one type of atom	Cu, O2, Cl2
Compound	Chemically combined elements, fixed ratio	NH3, C6H12O6, SO2
Homogeneous Mixture	Uniformly distributed components	Salt water, air
Heterogeneous Mixture	Non-uniformly distributed components	Chicken noodle soup, cereal and milk

Additional info:

• Valence electrons are the electrons in the outermost shell and determine chemical reactivity.

• Transition metals may have variable charges; always check the compound formula for correct charge assignment.

• Polyatomic ions are ions composed of more than one atom (e.g., NH4+, SO42-).