In-Depth Notes on Isotopes, Ions, and Electron Counts

Isotopes and Their Notation

• Distinction between different isotopes is crucial.
• "ACX notation" refers to a specific way to represent isotopes where:
• Bottom number typically indicates the atomic number (number of protons).
• Top number indicates mass number (total number of protons and neutrons).

Charge Balance in Atoms

• Atoms typically have an equal number of positive (protons) and negative (electrons) particles.
• When there is an imbalance, it indicates the atom is an ion (cation or anion).
• Example: If an atom loses electrons, it becomes a cation (positively charged ion).
• When there are more protons than electrons, the atom's overall charge is positive.

Consequences of Ionic Changes

• Change in charge leads to a smaller average atomic radius due to increased nuclear attraction from fewer electrons.

Types of Ions

• Cations: Positively charged ions formed by the loss of electrons.
• Example referenced: Loss of 2 electrons results in a 2+ charge.
• Calculation for this result might come from knowing the starting electron count.
• Anions: Negatively charged ions formed by the gain of electrons.
• Example symbol for an anion with a charge of -1 is represented as "R-".

Number Calculation

• To find the number of electrons in any ion, you adjust based on gained or lost electrons.
• For a neutral atom with 53 protons, after gaining 1 electron, the total electron count becomes 54.
• For an atom that started with 56 protons but lost 2 electrons, the electron count post-loss would be 54 (i.e. 56 – 2).
• Emphasizing the concept of significant figures when reading from periodic tables:
• Typical periodic tables may have up to 6 significant figures for certain isotopes.
• Depending on the context, fewer significant figures may suffice.

Review Questions

• Checking understanding on cation examples.
• Identifying the final electron counts based on modification of protons affects on atomic charge.