chapter 3

Atomic Structure and Stability

• The goal of atoms in bonding is to achieve a stable configuration, typically by having eight electrons in the outer shell, known as the octet rule.

• Lithium (Li) example:

  • First shell holds 2 electrons.

  • Second shell can hold 8 electrons.

  • Atoms strive for this stable arrangement.

Alkali Metals: Reactivity and Trends

• Group 1 elements (alkali metals) have one valence electron.

• These elements lose one electron to achieve stability, making them highly reactive.

• Reactivity increases down the group:

  • As atoms get larger, the outer electrons are further from the nucleus and experience less positive charge, making them easier to lose.

• Cesium (Cs), located lower in the group, can lose its single outer electron very easily, resulting in violent reactions.

Group Names to Remember

• Group 1: Alkali Metals

• Group 2: Alkaline Earth Metals

• Group 7: Halogens

• Group 8: Noble Gases

Electron Configuration and Magnetism

• Understanding whether an element is paramagnetic or diamagnetic can be determined through the abbreviated electron configuration and orbital diagrams.

• Example Elements:

  • Manganese (Mn)

  • Indium (In)

Electron Configuration Rules

• Fill electron configurations by groups:

  • For d-block elements in Row 4, use 3D; in Row 5, use 4D.

  • The f-block elements are shifted by two rows (f3 corresponds to 4f).

• Know that electron configurations can be complex due to varying subshell orders.

Upcoming Test and Review Schedule

• Review session: Thursday; topics to be discussed will be outlined on the review sheet.

• Practice test available online; answers will be provided during the review.

• Test dates: Available for taking on Friday or Tuesday.

• Testing procedures:

  • ID required

  • Calculator needed

  • Two-hour time limit but flexible on enforcement.

Periodic Trends

• Atomic Size:

  • Increases down groups (more shells added).

  • Decreases across a period due to increased nuclear charge pulling electrons closer.

• Cations (positive ions): Smaller than their neutral atoms.

• Anions (negative ions): Larger than their neutral atoms.

Ionization Energy

• Energy required to remove an electron:

  • Increases across periods (more energy needed to remove an electron due to stronger nuclear charge).

  • Decreases down groups (electrons are further from the nucleus).

  • Exceptions exist (groups 2 to 3 and 5 to 6).

• For example, phosphorus has a higher ionization energy than magnesium.

Electron Affinity and Trends

• This refers to how likely an atom is to gain an electron.

• General trend: increasing affinity across a period and decreasing down a group.

Properties of Metals and Non-Metals

• Metals (typically left of the periodic table):

  • Malleable and ductile.

  • Form positive ions (cations) by losing electrons.

• Non-metals (right side, including halogens):

  • Tend to gain electrons making them reactive.

Metallic Character

• Metals have increasing metallic character as you move down a group and across to the left on the periodic table.

Final Notes for Test Preparation

• Review materials: iClickers, quizzes, practice tests.

• Practice worksheets provided with answer keys for study.

• Importance of thorough practice; everything included in material will reflect on the test.

• Stay organized and proactive in reviewing content prior to the exam.