Chem Terminology

Atomic Structure

• Atom: The smallest unit of an element, made up of protons, neutrons, and electrons.

• Proton: A positively charged subatomic particle found in the nucleus of an atom.

• Neutron: A neutral subatomic particle found in the nucleus of an atom.

• Electron: A negatively charged subatomic particle that orbits the nucleus.

• Atomic Number: The number of protons in an atom, determines the element’s identity.

• Atomic Mass: The total mass of an atom, roughly the sum of protons and neutrons.

• Ion: An atom or molecule that has gained or lost electrons, resulting in a charge.

  • Cation: A positively charged ion (lost electrons).

  • Anion: A negatively charged ion (gained electrons).

The Periodic Table

• Group (Column): A vertical column on the periodic table; elements in the same group have the same number of valence electrons and similar chemical properties.

• Period (Row): A horizontal row on the periodic table; elements in the same period have the same number of electron shells.

• Metals: Elements that are typically good conductors of heat and electricity, and are found on the left side of the periodic table.

• Nonmetals: Elements that are poor conductors of heat and electricity, and are found on the right side of the periodic table.

• Metalloids: Elements that have properties of both metals and nonmetals; found along the staircase on the periodic table.

• Noble Gases: Group 18 elements, known for being chemically inert (non-reactive).

Chemical Bonding

• Ionic Bond: A bond formed between a metal and a nonmetal where electrons are transferred from one atom to another, resulting in the formation of ions.

• Covalent Bond: A bond formed between two nonmetals where electrons are shared.

• Metallic Bond: A bond found in metals where electrons are free to move, creating a "sea of electrons."

• Polyatomic Ion: An ion made up of more than one atom, such as NO3−\text{NO}_3^-NO3−​ or SO42−\text{SO}_4^{2-}SO42−​.

Naming Compounds

• Ionic Compounds: Formed between a metal and a nonmetal. The metal gives up electrons (forms a cation), and the nonmetal gains electrons (forms an anion).

  • Example: Sodium chloride (NaCl)

• Molecular (Covalent) Compounds: Formed between two nonmetals, where electrons are shared.

  • Example: Carbon dioxide (CO₂)

• Roman Numerals: Used to indicate the charge of multivalent metals in ionic compounds (e.g., Iron (III) chloride means iron has a +3 charge).

• Polyatomic Ions: Groups of atoms with a charge. Example: Nitrate (NO3−\text{NO}_3^-NO3−​), Sulfate (SO42−\text{SO}_4^{2-}SO42−​).

Bohr-Rutherford Model

• Bohr-Rutherford Diagram: A representation of an atom, showing the nucleus (protons and neutrons) and the electron shells around it.

  • First Shell: Can hold up to 2 electrons.

  • Second Shell: Can hold up to 8 electrons.

  • Third Shell: Can hold up to 18 electrons.

  • Fourth Shell: Can hold up to 32 electrons.

• Electron Configuration: The arrangement of electrons in an atom’s shells.

Physical vs. Chemical Changes

• Physical Change: A change that alters the appearance or state of a substance without changing its chemical composition (e.g., melting, freezing, dissolving).

• Chemical Change: A change that results in the formation of new substances with different chemical properties (e.g., burning wood, rusting iron).

Types of Elements

Period: A horizontal row on the periodic table. Elements in the same period have the same number of electron shells.

• Example: Sodium (Na) and Magnesium (Mg) are in Period 3.

Group: A vertical column on the periodic table. Elements in the same group have similar chemical properties and the same number of valence electrons.

• Metals: Elements that are typically good conductors of heat and electricity.

  • Example: Sodium (Na), Iron (Fe)

• Nonmetals: Elements that are poor conductors of heat and electricity.

  • Example: Oxygen (O), Sulfur (S)

• Metalloids: Elements that have properties of both metals and nonmetals.

  • Example: Boron (B), Silicon (Si)

• Alkali Metals: Group 1 elements, highly reactive metals (e.g., Sodium (Na), Potassium (K)).

• Alkaline Earth Metals: Group 2 elements, less reactive than alkali metals (e.g., Calcium (Ca), Magnesium (Mg)).

• Halogens: Group 17 elements, highly reactive nonmetals (e.g., Chlorine (Cl), Fluorine (F)).

• Noble Gases: Group 18 elements, chemically inert (e.g., Neon (Ne), Argon (Ar)).

Other Important Terms

• Valence Electrons: The electrons in the outermost shell of an atom that are involved in chemical bonding.

• Oxidation State (Charge): The charge of an ion formed by an element; it indicates how many electrons an atom has gained or lost.

• Chemical Formula: A representation of a compound using symbols for the elements and numbers to indicate the ratio of atoms.

  • Example: NaCl (sodium chloride), H₂O (water).