Essential Chemistry Concepts: Atoms, Gases, and Reactions
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Fundamental Atomic Structure
- Atom: The smallest unit of a substance that retains its chemical properties, composed of subatomic particles common to all elements.
- Atomic Number (Z): The number of protons in an atom's nucleus. In a neutral atom, this equals the number of electrons.
- Mass Number (A): The total number of particles in the nucleus (protons + neutrons).
- Isotopes: Varieties of the same element with the same atomic number (Z) but a different number of neutrons, resulting in a different mass number (A).
Chemical Quantities and Formulas
- Mole (mol): The amount of substance containing 6.022 × 1023 particles, known as Avogadro's number.
- Empirical Formula: Indicates the simplest whole-number ratio of atoms in a molecule.
- Molecular Formula: Indicates the actual number of atoms of each element in a molecule; it is a multiple of the empirical formula.
Principles of Ideal Gases
The general law of ideal gases is expressed as PV = (m/M)RT, where:
- Boyle's Law (T constant): P1V1 = P2V2
- Charles's Law (P constant): V/T = V1/T1
- Gay-Lussac's Law (V constant): P/T = P1/T1
In these equations, m is the mass of the gas (g), M is the molar mass (g/mol), and d represents density.
Chemical Reactions and Matter
- Chemical Reaction: A process where reactants are transformed into products with distinct properties.
- Law of Conservation of Mass: The total mass of reactants must equal the total mass of products.
- Limiting Reagent: The reactant that is consumed completely, thereby limiting the amount of product formed.
Spectra and Atomic Orbitals
- Spectrum: A set of electromagnetic radiation of varying wavelengths. It can be continuous or discontinuous (line spectrum). It may also be classified as an emission or absorption spectrum.
- Orbital: The region of space around the nucleus where there is a high probability of finding an electron.