Periodic Trends and Atomic Properties

Periodic Trends Overview

Exam Details

• Exam on Chapter 7 and 8 scheduled for next Thursday.

Key Concepts of Periodic Trends

• Focus on observing and predicting properties of atoms using the periodic table.

• Trends can be analyzed in two dimensions:

  • Groups (Vertical)

  • Periods (Horizontal)

Atomic Radius (Size of Atoms)

• Definition: The size of an atom, often depicted as a sphere for illustrative purposes.

• Trends in Atomic Radius:

  • Down a Group (e.g. Group 1: H, Li, Na): Atomic size increases.

  • As you move down the group, additional electron shells are added (e.g.,

    • Hydrogen: 1 shell (1s¹)

    • Lithium: 2 shells (2s¹)

    • Sodium: 3 shells (3s¹)).

  • Across a Period (e.g. Left to Right): Atomic size decreases.

  • Nuclear charge increases as protons are added, attracting electrons more strongly and pulling them closer, thus reducing the size.

Mnemonic Devices

• Snowman Analogy: Visualize a snowman increasing in size as you go down the group.

Practice Questions on Atomic Radius

• Compare sizes of atoms:

  • Indium (In) vs Aluminum (Al): Indium is larger.

  • Silicon (Si) vs Nitrogen (N): Silicon is larger.

  • Phosphorus (P) vs Carbon (C): Carbon is larger.

  • Tin (Sn) vs Silicon (Si): Tin is larger.

  • Bromine (Br) vs Gallium (Ga): Gallium is larger.

  • Bismuth (Bi) vs Tin (Sn): Bismuth is larger.

  • Selenium (Se) vs Tin (Sn): Tin is larger.

Largest and Smallest Atoms

• Largest Atom: Francium (Fr)

• Smallest Atom: Exist as ions (e.g., Lithium ion, Li⁺) which then exhibit a higher effective nuclear charge than their neutral counterparts.

Ionization Energy

• Definition: The energy required to remove an outer shell electron from an atom.

• Trends in Ionization Energy:

  • Across a Period: Ionization energy increases due to the stronger nuclear attraction from the increased positive charge.

  • Down a Group: Ionization energy decreases because electrons are farther from the nucleus and are less tightly held.

Practice Questions on Ionization Energy

• Which has the highest ionization energy:

  • Bromine (Br) vs Bismuth (Bi): Choose Bromine (higher up and right).

  • Sodium (Na) vs Rubidium (Rb): Choose Sodium (higher up).

  • Arsenic (As) vs Astatine (At): Choose Arsenic (higher up).

  • Phosphorus (P) vs Tin (Sn): Choose Phosphorus (higher up).

Metallic vs Non-Metallic Character

• Definition of a Metal: An element that typically conducts electricity, is shiny, and easily loses outer electrons.

• Trends:

  • Metals are usually found on the left side of the periodic table and have lower ionization energies.

  • Nonmetals are found on the right and have higher ionization energies.

• Best Metal: Francium (Fr)

• Worst Metal: Helium (He)

Summary of Key Points

• Atomic size increases down a group and decreases across a period.

• Ionization Energy increases across a period and decreases down a group.

• Metals have low ionization energies and are located on the left of the periodic table, whereas nonmetals have high ionization energies and are found on the right.

In Marvel terms, think of the periodic trends like a superhero lineup: each character (atom) has unique abilities (properties) that change depending on their environment (the periodic table). For example, as you move down a group (like the Avengers forming a team) each character gets bigger and stronger because they gain more experience (electron shells), making them more powerful in battle. However, as you go across a period (like recruiting new heroes), their abilities can become more refined and efficient, rather than just bigger – they have stronger powers due to better training (increased nuclear charge).

In Top Gun terms, consider the atomic radius as the size of your aircraft. As you go down a group, it's like moving up to a larger jet (think from a F-18 to a more powerful airframe); you have more fuel tanks and equipment (electron shells). However, as you move across a period, the jets become sleeker and more aerodynamic, packing more energy and speed into a smaller size due to superior engineering (increased nuclear charge pulling electrons closer).

When it comes to ionization energy, think about how hard it is to eject a pilot from the cockpit in an intense dogfight. As you go down the group (like moving to less experienced pilots), it's easier to eject (lower ionization energy). But across a period, the pilots are more skilled and harder to eject due to their refined techniques and training (higher ionization energy).