Chemistry topic test:

Chemistry Topics Overview

ATOMS

• The basic unit of matter, consisting of three main particles: protons, neutrons, and electrons.

• Protons (positive charge) and neutrons (no charge) are found in the nucleus, while electrons (negative charge) orbit the nucleus.

DETERMINING THE NUMBER OF ELECTRONS

• The number of electrons in a neutral atom is equal to the number of protons (atomic number).

• In ions, the number of electrons differs from the number of protons:

  • Anions (negatively charged) have more electrons than protons.

  • Cations (positively charged) have fewer electrons than protons.

ELECTRON ARRANGEMENT

• Electrons are arranged in energy levels or shells around the nucleus.

• The arrangement follows the Aufbau principle, Hund's rule, and the Pauli exclusion principle.

• The distribution of electrons among the various orbitals determines an atom's chemical properties.

IONS

• Charged entities formed when atoms gain or lose electrons.

• Cations and anions:

  • Cations: Formed by losing electrons (e.g., Na⁺).

  • Anions: Formed by gaining electrons (e.g., Cl⁻).

NAMING COMPOUNDS

• The systematic way of naming chemical compounds based on the elements involved.

• Ionic compounds generally use the names of both the metal cation and the non-metal anion (e.g., NaCl is named sodium chloride).

• Covalent compounds use prefixes to indicate the number of atoms (e.g., CO₂ is named carbon dioxide).

CHEMICAL FORMULA WRITING

• A representation of a chemical compound showing the types and numbers of atoms present.

• Empirical formulas show the simplest whole-number ratio of elements (e.g., CH₄ for methane).

• Molecular formulas provide the actual number of each type of atom (e.g., C₂H₆ for ethane).

BALANCING EQUATIONS

• The process of ensuring that the number of atoms for each element is the same on both sides of a chemical equation.

• This is done by adjusting the coefficients in front of the compounds until the equation is balanced.

• Importance: Follows the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a chemical reaction.