Modern Atomic Theory and Periodic Table

Modern Atomic Theory

• Investigation 1 Experience 4
• The quantum mechanical model, similar to the Bohr model, restricts electron energies to specific values.
• Crucially, the quantum mechanical model doesn't define a precise electron pathway around the nucleus.
• For each energy level, an atomic orbital exists, where electron presence probability is high.

Periodic Table

• Atomic number order is crucial; periodic properties repeat accordingly.
• Periods in the Periodic Table show a pattern in element properties' change across them. However, properties repeat regularly.
• Elements in a group share identical properties.

Shell Model

• The shell model uses orbitals distinguished by letters and energy levels.
• The s orbital holds up to 2 electrons with 1 orbital.
• The p orbital holds up to 6 electrons with 3 orbitals.
• The d orbital holds up to 10 electrons with 5 orbitals.
• The f orbital holds up to 14 electrons with 7 orbitals.
• Each orbital holds a maximum of 2 electrons.

Electron Configuration using Crazy Arrows

• Use arrow sequence to model electron positioning.
• Stop when enough electrons are plotted based on the element.
• Illustrates electron filling order through the arrows' trajectory.

Calculating Valence Electrons

• Group number minus 10 for groups 14-18 (except helium, which has 2).
• Groups 3 to 12 are transition metals. Determining valence electrons is problematic here.

Electrons in Atoms- Investigation 1 Experience 5

• This topic is about the distribution of electrons in atoms.

Lewis Dot Structure

• To represent valence electrons, use the element symbol and dots around it.
• Place a dot for each valence electron on each side of the element symbol.

Orbital Notation

• Model electron configurations by using arrows and boxes for orbitals.
• s orbitals have 1 box, p orbitals have 3, d orbitals have 5, and f orbitals have 7.
• Follow Hund's Rule, Pauli Exclusion Principle, and Aufbau's principle.

Hund's Rule and Pauli's Exclusion Principle

• Hund’s Rule: Electrons use separate orbitals before pairing up.
• Pauli's Exclusion Principle: Each electron in an atom has a unique set of four quantum numbers.
• Electrons occupy orbitals individually first before doubling up on the same orbital.

Aufbau Principle

• Electrons fill orbitals in order starting with the lowest energy level, then progressing to higher levels.
• This is done by following the arrow configuration sequence.

Noble Gas Notation

• Summarizes electron configuration using noble gases' core electron configurations.
• Identify the noble gas before the element of interest in the Periodic Table (precede it).
• Place it in brackets, which represent core electrons.
• Continue normal electron configuration from the preceding noble gas and add remaining electrons to fully describe the element's configuration.

The Periodic Table: An Overview- Investigation 2 Experience 1

• History of the Periodic Table's development.
• Dmitri Mendeleev's role emphasized.

The Modern Periodic Table

• The modern periodic table organizes elements by increasing atomic number.
• Elements with similar properties fall within the same group.
• Across a period, properties change; down a group, recurring properties appear.

The 3 Main Categories of the Periodic Table

• Metals: Shiny, solid at room temp (except Hg), good conductors, malleable, ductile.
• Non-Metals: Solids, liquids, gases, brittle, poor conductors.
• Metalloids: Combine metal and non-metal characteristics.

Atomic Radius

• Half the distance between two identical nuclei.
• Influenced by electron shells and effective nuclear charge.

Atomic Radius Trend

• Across a period, atomic radius decreases.
• Down a group, atomic radius increases.

Effective Nuclear Charge (Zeff)

• The net positive charge experienced by an electron.
• Calculated by subtracting the atomic number from the total number of electrons.
• Core electrons are subtracted.

Zeff Trend

• Across a period, Zeff increases.
• Down a group, Zeff is relatively constant.

Shielding Effect (S.E)

• Valence electrons are shielded by core electrons.
• The greater the number of energy levels, the stronger the shielding effect.

Shielding Effect Trend

• Shielding effect increases down a group.
• Shielding effect is relatively constant across a period because the number of energy shells remains the same.

Cations and Anions

• Cations form when atoms lose electrons, becoming positively charged.
• Anions form when atoms gain electrons, becoming negatively charged.
• Metals form cations; nonmetals form anions.

Cations vs. Parent/Neutral Atom

• Cations are smaller than their neutral atom counterparts.

Anions vs. Parent/Neutral Atom

• Anions are bigger than their neutral atom counterparts.
• Anions gain electrons to reach a full outer shell and thus a negatively charged ion.

Ionic Radius (l.r)

• Measure of the ion's size (cation or anion).
• Decreases across a period because of the increase in Zeff.
• Increases down a group due to increased energy levels.

Ionization Energy (I.E)

• Energy required to remove an electron.
• Easier to remove electrons from atoms with a larger size/lower Zeff.
• Greater stability is associated with higher ionization energy.

Size vs I.e Trend

• As size decreases, ionization energy increases.
• As size increases, ionization energy decreases.
• Across a period ionization energy generally increases.
• Down a group ionization energy generally decreases.

Electron Affinity (EA)

• Energy change when an atom gains an electron.
• Generally more negative across a period.
• Generally less negative down a group.

Electron Affinity Trend

• Across a period, electron affinity generally increases with increasing nuclear charge.
• Down a group, electron affinity generally decreases due to increased atomic radius.

Explore the fundamentals of Modern Atomic Theory, the structure of the Periodic Table, and the Shell Model. This quiz covers electron configurations, energy levels, and the arrangement of elements based on atomic number. Test your knowledge on how these concepts interconnect in understanding atomic structure.