Understanding Matter: States, Atomic Structure, and Bonding

Posted on Apr 11, 2025 in Chemistry

Matter: The material part of the universe. It’s anything that has mass and occupies space.

States of Matter

Solids: Have a definite shape and occupy a definite volume. The particles that make up solids are very close together and aren’t moving around very much (they have vibrations). They often have an organized structure of repeating patterns called a crystal lattice.

Liquids: Have no definite shape, but they do have a definite volume. The particles in liquids are much farther apart than the particles in solids, and they’re also moving around much more. The attractive forces among them (the particles) aren’t as strong as they are in solids.

Gases (Vapor): Have no definite shape and no definite volume. Particles are much farther apart than they are in solids or liquids. They’re moving relatively independently of each other.

Atomic Structure

Atomic Mass: Neutrons (n⁰) + Protons (p⁺)

Atomic Number: Protons (p⁺) = Electrons (e⁻)

Phase Transitions

Boiling Point: The temperature at which a liquid begins to boil. (Ice – Water – Steam (Vapor))

Freezing Point (Melting Point): When particles are cooled, energy is reduced. The point at which a liquid is able to become a solid.

Sublimation: The transition of a substance directly from the solid to the gaseous state without passing through the liquid state.

Density

Density: D = m/v

Pure Substances and Mixtures

Pure Substances: Have a definite and constant composition. The composition of a pure substance doesn’t change.

  • An element is composed of a single kind of atom.
  • A compound is composed of two or more elements in a specific proportion.

Mixtures: Are physical combinations of pure substances that have no definite or constant composition.

  • Homogeneous Mixtures: Sometimes called solutions, are relatively uniform in composition; every portion of the mixture is like every other portion.
  • Heterogeneous Mixtures: Have a composition that varies from position to position within the sample.

Subatomic Particles and Atomic Nucleus

Subatomic Particles: The atom is the smallest part of matter that represents a particular element.

Nucleus: The center of the atom, containing protons and neutrons. It is very small and very dense when compared to the rest of the atom.

Ions

Ions:

  • Positive = Cations
  • Negative = Anions

Chemical Bonds

Ionic Compounds (Solid State)

  1. Crystalline solids (made of ions).
  2. High melting and boiling points.
  3. Conduct electricity when melted.
  4. Many are soluble (easy to dissolve) in water but not in nonpolar liquids (liquids without electrical charge).

Covalent Compounds (3 States)

  1. Gases, liquids, or solids (made of molecules).
  2. Low melting and boiling points.
  3. Poor electrical conductors in all phases.
  4. Many are soluble in nonpolar liquids but not in water.

Metallic Bonds

  1. Conduct heat.
  2. Conduct electricity.
  3. Generally high melting and boiling points.
  4. Strong.
  5. Malleable (can be hammered or pressed out of shape without breaking).
  6. Ductile (able to be drawn into a wire).
  7. Metallic luster.
  8. Opaque.

Atomic Models

Bohr Model: Shows that the electrons in atoms are in orbits of differing energy around the nucleus. Bohr used the term energy levels to describe these orbits of differing energy. The energy of an electron is quantized, meaning electrons can have one energy level or another but nothing in between. The energy level an electron normally occupies is called its ground state. An excited state is when the electron has less energy. Bohr found that the closer an electron is to the nucleus, the less energy it needs, but the farther away it is, the more energy it needs. So Bohr numbered the electrons’ energy levels. The higher the energy-level number, the farther away the electron is from the nucleus and the higher the energy.

Quantum Mechanical Model: Scientists had to replace Bohr’s orbits with orbitals (sometimes called electron clouds), volumes of space in which there is likely to be an electron.

Bonding Types

Covalent Bond: Share electrons.

Ionic Bond: One gives an electron to another.

Metallic Bond: Electrons are not completed, but the atoms of the last layer move, and they act as if they are completed.

Electron Configurations

Helium (He): 1s²

Neon (Ne): 1s²2s²2p⁶

Sodium (Na): 1s²2s²2p⁶3s¹

Argon (Ar): 1s²2s²2p⁶3s²3p⁶

Krypton (Kr): 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶

Xenon (Xe): [Kr] 5s²4d¹⁰5p⁶

Radon (Rn): [Xe] 6s²4f¹⁴5d¹⁰6p⁶

Electron Configuration Order: 1s²/2s²/2p⁶/3s²/3p⁶/4s²/3d¹⁰/4p⁶/5s²/4d¹⁰/5p⁶/6s²/4f¹⁴/5d¹⁰/6p⁶/7s²/5f¹⁴/6d¹⁰/7p⁶…