6142 M1 | [1] General Chemistry

Empirical Formula

Gives the simplest form of a substance (e.g., H₂O₂ to HO).

Molecular Formula

Gives the actual number of atoms of each element in the smallest unit of a substance (e.g., H₂O₂).

Structural Formula

Shows the arrangement of atoms.

Electronic Formula

Shows the Lewis structure.

Molar Mass

Mass of 1 mole of any substance expressed in grams.

Unit of Molar Mass

Gram (g).

Atomic Mass Unit (AMU)

1/12 the mass of an individual Carbon-12 atom.

Mole

Contains Avogadro’s number (6.022 × 10²³).

Avogadro’s Number

6.022 × 10²³ elementary entities.

Number of Neutrons

Atomic Mass − Atomic Number.

Atomic Number

Number of protons and electrons.

Atomic Mass

Sum of protons and neutrons.

Number of Neutrons in ¹⁰⁸₄₇Ag

108 − 47 = 61 neutrons.

Isotopes

Substances with the same atomic number but different numbers of neutrons or different mass numbers.

Protium

¹₁H; normal hydrogen.

Deuterium

²₁H; heavy hydrogen.

Tritium

³₁H; radioactive hydrogen.

Isobars

Different nuclides having the same mass number but different atomic numbers.

Isotones

Atoms having the same number of neutrons.

Isomers

Substances having the same molecular formula but different structures.

Nucleons

Protons or neutrons that determine the atom’s mass number.

Polyatomic Molecule

A molecule composed of more than two atoms.

Characteristics of Molecules

Molecules do not possess charges; otherwise, they are ions.

O₂

Homonuclear diatomic molecule.

CO

Diatomic compound.

CO₃²⁻

Polyatomic ion or radical.

CO₂

Polyatomic molecule and compound.

Ionization Energy

Amount of energy needed to remove an electron from an atom to form a cation.

Electronegativity

Ability of an atom to attract electrons.

Electron Affinity

Gain of electrons.

Atomic Size

Shortest distance between the atom’s nucleus and the valence shell of the atom.

Heisenberg Uncertainty Principle

It is impossible to accurately determine simultaneously the position and motion of an electron.

Pauli’s Exclusion Principle

No two electrons in an atom can have the same four quantum numbers.

Aufbau Principle

Building-up principle.

Planck’s Quantum Theory

Atoms and molecules could emit or absorb energy in discrete quantities in the form of electromagnetic radiation or quantum numbers.

Principal Quantum Number

Represents the energy level or distance from the nucleus.

Angular or Azimuthal Quantum Number

Gives the sublevel, shape, or approximate size of the electron cloud.

Magnetic Quantum Number

Determines the orientation of the orbital in space.

Spin Quantum Number

Describes two electrons moving in opposite directions or electron spin.

Representative Elements

Elements in Groups 1A to 7A with incomplete S or P orbitals.

Transition Elements

Elements in Groups 1B to 8B with incomplete D orbitals.

Inert Gases

Elements in Group 8A with filled S or S and P orbitals.

Inner Transition Elements

Lanthanides and actinides with incomplete F orbitals.

Representative Elements — Group 1A

Alkali metals; outer configuration S¹; 1 valence electron; lose electrons; form cations; oxidation number +1 (e.g., Na⁺).

Representative Elements — Group 2A

Alkaline earth metals; outer configuration S²; 2 valence electrons; lose electrons; form cations; oxidation number +2 (e.g., Sr²⁺).

Representative Elements — Group 3A

Boron group; outer configuration S²P¹; 3 valence electrons; lose electrons; form cations; oxidation number +3 (e.g., Al³⁺).

Representative Elements — Group 4A

Carbon group or crystallogens; outer configuration S²P²; 4 valence electrons; metalloids; either lose or gain electrons; form cations or anions; oxidation number +4/−4 (e.g., Si⁴⁺).

Representative Elements — Group 5A

Nitrogen group or pnictogens; outer configuration S²P³; 5 valence electrons; gain electrons; oxidation number −3 (e.g., N³⁻).

Representative Elements — Group 6A

Oxygen group or chalcogens; outer configuration S²P⁴; 6 valence electrons; nonmetals; gain electrons; form anions; oxidation number −2 (e.g., O²⁻).

Representative Elements — Group 7A

Halogens; outer configuration S²P⁵; 7 valence electrons; gain electrons; oxidation number −1 (e.g., Cl⁻).