Atomic Structure & Bonding

Ionic vs. Covalent Bonding

Chemical bonds are the forces that hold atoms together in compounds. The two main types are ionic bonds and covalent bonds, which differ in how electrons are distributed between atoms.

• Ionic Bonds: Formed when one atom transfers electrons to another, resulting in oppositely charged ions that attract each other. Typically occurs between a metal and a non-metal.

• Covalent Bonds: Formed when two atoms share pairs of electrons, allowing both to achieve a stable electron configuration. Usually occurs between two non-metals.

• Example: Sodium chloride (NaCl) is an ionic compound, while water (H2O) is a covalent compound.

Atomic Properties of Sodium

Each element is defined by its atomic structure, specifically the number of protons, neutrons, and electrons.

• Atomic Number: The number of protons in the nucleus. For sodium, this is 11.

• Mass Number: The sum of protons and neutrons. For sodium, with 11 protons and 12 neutrons, the mass number is .

• Example: Sodium (Na) has atomic number 11 and mass number 23.

The Stability of Noble Gases

Noble gases (Group 18 of the periodic table) are characterized by their lack of chemical reactivity. This is due to their full valence electron shells, which make them energetically stable.

• Key Point: Noble gases rarely form bonds because their outermost shell is already complete (8 electrons, or 2 for Helium).

• Example: Helium, neon, and argon are common noble gases.

Chemical Reactions & Acids/Bases

Balancing Chemical Equations

Balancing chemical equations ensures the Law of Conservation of Mass is followed, meaning atoms are neither created nor destroyed in a reaction.

• Unbalanced Equation:

• Balanced Equation:

• Explanation: The coefficients are adjusted so that the number of hydrogen and oxygen atoms is equal on both sides of the equation.

Identifying Acids and Bases

The pH scale is used to determine whether a substance is acidic, neutral, or basic (alkaline) based on its hydrogen ion concentration.

• Acids: pH values from 0–6; strong acids have lower pH values (e.g., pH 2).

• Neutral: pH value of 7.

• Bases: pH values from 8–14; strong bases have higher pH values.

• Color Indicators: Acids are often red/orange, neutral is green, and bases are blue/purple on pH indicator strips.

Summary Table: Types of Chemical Bonds

Summary Table: pH Scale Classification

Additional info: The notes cover core concepts from general chemistry chapters including atomic structure, chemical bonding, chemical reactions, and acids/bases. The included images directly reinforce the explanations of ionic/covalent bonding and the pH scale.