Unit 1 Test Chem — Fundamental Properties of Matter + 5 more topics

Intermolecular forces (IMFs) are attractive forces that exist between molecules. Don't confuse them with intramolecular forces (like covalent or ionic bonds), which are the forces within a single molecule or compound, holding atoms together. IMFs are significantly weaker, but they control many physical properties like melting points, boiling points, and solubility.

There are three main types of IMFs, listed from weakest to strongest:

You've covered several key areas in Unit 1:
* Atomic Structure: Protons, neutrons, electrons, isotopes, atomic number, mass number.
* Periodic Table Trends: How elements are organized, periodicity (e.g., electronegativity, ionization energy, atomic radius).
* Chemical Bonding: Ionic, covalent (polar/nonpolar), metallic bonds; Lewis structures.
* Stoichiometry: Moles, molar mass, empirical and molecular formulas, balancing equations, limiting reactants, theoretical yield.
* States of Matter & Intermolecular Forces: Solids, liquids, gases; hydrogen bonding, dipole-dipole, London dispersion forces.

Effective nuclear charge (Zeff) is the net positive charge felt by an electron. Inner electrons "shield" outer electrons from the full pull of the nucleus. As you move across a period, the number of protons increases, but the number of inner shielding electrons stays the same, so Zeff increases.

Photo by Steve A Johnson on Pexels

Matter is anything that has mass and occupies space. We describe matter using two main types of properties: physical properties and chemical properties.

Photo by Cup of Couple on Pexels

Chemical bonding is all about how atoms interact to become more stable. This stability is often achieved when an atom's outermost electron shell (the valence shell) is full, like the noble gases (e.g., Helium, Neon, Argon). These outer electrons are called valence electrons, and they're the ones involved in bonding.

When we talk about molecular geometry, we're really looking at how the atoms in a molecule are arranged in three-dimensional space. This arrangement is crucial because it influences many of a molecule's properties, like its boiling point, solubility, and reactivity. The Valence Shell Electron Pair Repulsion (VSEPR) theory is our main tool here. It states that electron pairs (both bonding and non-bonding or lone pairs) around a central atom will orient themselves as far apart as possible to minimize repulsion.