Chemistry Chapter 5 Quiz

Atomic Theory

• Dalton's Atomic Theory (1808): Proposed atoms as indivisible building blocks of matter, atoms of an element have identical properties, and atoms combine in specific ratios.
• J.J. Thomson (1897): Discovered the electron, suggesting that atoms are not indivisible but contain smaller particles. Proposed a "plum pudding" model of the atom with negatively charged electrons embedded in a positively charged sphere.
• Ernest Rutherford (1911): Discovered the atomic nucleus, a dense, positively charged center. Proposed a model where most of the atom is empty space with the nucleus at the center.
• Niels Bohr (1913): Developed a model where electrons orbit the nucleus in specific energy levels.
• James Chadwick (1932): Discovered the neutron, a neutral subatomic particle found in the nucleus, completing the understanding of the subatomic structure of the atom.
• Schrodinger/de Broglie (1930): Developed a more sophisticated quantum mechanical model that describes electrons as having wave-like properties and existing in orbitals.

Atomic Structure

• Subatomic Particles:
  • Protons (p+): Positively charged particles found in the nucleus, determining the atomic number.
  • Neutrons (n°): Neutral particles found in the nucleus, contributing to the atomic mass.
  • Electrons (e-): Negatively charged particles orbiting the nucleus, arranged in electron shells/energy levels. The maximum number of electrons in each energy level determines the structure and properties of the atom.
• Atomic Mass: Measured in atomic mass units (amu). The sum of protons and neutrons in an atom.
• Atomic number: The number of protons in the nucleus of an atom. It determines the unique nature of each element.

The Periodic Table

• Dmitri Mendeleev: Developed the periodic table based on the arrangement of elements by increasing atomic weight, allowing for predictions of undiscovered elements.
• Organization: Elements are organized by increasing atomic number (number of protons), categorized into metals, non-metals, and metalloids, and arranged in periods and groups based on similar properties.
• Periods: Rows on the table, show how electrons fill energy levels.
• Groups/Families: Columns on the table, show elements with similar chemical properties.
• Isotopes: Atoms of the same element with different numbers of neutrons. They have the same atomic number but different atomic masses (number of protons and neutrons).

Electron Dot Diagrams/Bohr Models

• Bohr model diagrams visualize atomic structures showing shells (or energy levels) with electrons at each shell. The shells can hold a maximum defined number of electrons.
• The number of valence electrons (outermost shell electrons) dictates an element's reactivity and chemical behavior.
• Electron dot diagrams (Lewis structures) are simpler visual representations of the structure, showing valence electrons as dots.

Ions

• Cations: Positively charged ions formed when atoms lose electrons.
• Anions: Negatively charged ions formed when atoms gain electrons.
• Isoelectronic: Ions that have the same electron configuration. They tend to have similar properties. Many compounds with ionic bonds form as a result of one element wanting to become isoelectronic with another.

Molecular Compounds

• Bonding: Molecules are formed when atoms bond together through electron sharing (usually covalently bonding).
• Properties: Vary from substances based on the elements (or atoms) participating.
• Naming: Compounds with more than one element involve using prefixes—these are prefixes that indicate the number of atoms of each type from each element.

Ionic Compounds

• Bonding: Ionic compounds form when atoms transfer electrons. The resulting charged particles (ions) form ionic bonds.
• Properties: Usually solid crystalline structures with high melting points; often soluble in water and can conduct electricity when dissolved.
• Naming: The name of the metal cation is listed first followed by the name of the non-metal anion.

Chemical Reactions

• Classification: Reactions are categorized by the types of changes occurring within molecules, or atoms. (eg. decomposition, single/double displacement)
• Balancing Equations: Demonstrating that matter is not lost nor created using coefficients for each element to make sure each atom of each element is balanced on both sides of the equation (reactants vs products).
• Identifying and predicting reactions: The reaction type helps predict the products, or the reactants.

States and Solubility

• States of matter: Physical states of matter are (s) solid, (l) liquid, (g) gas, (aq) aqueous (dissolved in water).
• Solubility: The ability of a substance to dissolve in another substance. Some compounds dissolve in water, others not.

Moles

• Concept: One mole of any substance contains Avogadro's number of particles. (6.02 x 10^23)
• Calculating moles: If you know the number of particles, you can calculate the number of moles.
• Atomic mass: The mass of one mole of an element in grams.
• Molar mass: The mass of one mole of a compound in grams.
• Conversions using moles: Conversion factors to connect the mass of a substance with the number of moles and, further, to the number of molecules/particles.

Acids and Bases

• Acids: Taste sour, react with metals to release hydrogen gas, and can conduct electricity when dissolved usually in water.
• Bases: Taste bitter, feel slippery; neutralize acid reactions in aqueous solutions.
• Indicators: Substances that change color to show whether a solution is an acid or a base. (e.g., litmus, phenolphthalein)