AP Chemistry Unit 7: Periodic Relationships among the Elements


  • To explain the development of the modern periodic table and the arrangement of elements on it as described in the Periodic Law
  • To relate electron configurations logically to the arrangement of elements on the periodic table and use this logic o explain some anomalies.
  • To explain trends in the size of atoms and ions based on their effective nuclear charge
  • To predict properties of an element or group of elements: ionization energy, electron affinity
  • To study the properties of representative elements across a period.

Course Goals and Essential Questions

  • How can we learn about things that are to small to see?
  • What relationships can I construct among basic concepts, skills, and understandings?
  • How can I best assess my own learning and progress?
  • How can I better use technology in my learning?
  • How can I become a better digital citizen?
  • How can I think more divergently, create, innovate?
  • How can I use my experience in chemistry to learn to think and communicate clearly, logically, and critically in preparation for college and a career?

Prior Knowledge

  • Atomic structure
  • Basic history of the development of the periodic table

Prior Skills

  • Find the number of protons, neutrons, electrons for any element, given a periodic table
  • Write electron configurations for any element, using the building-up principal and/or location of the element on the periodic table

Enduring understanding 1.C:
Elements display periodicity in their properties when the elements are  organized according to increasing atomic number. This periodicity can  be explained by the regular variations that occur in the electronic structures of atoms. Periodicity is a useful principle for understanding properties and predicting trends in properties. Its modern-day uses range from examining the composition of materials to generating ideas for designing new materials.

Although a simple shell model is not the currently accepted best model of atomic structure, it is an extremely useful model that can be used qualitatively to explain and/ or predict many atomic properties and trends in atomic properties. In particular, the arrangement of electrons into shells and subshells is reflected in the structure of the periodic table and in the periodicity of many atomic properties. Many of these trends in atomic properties are important for understanding the properties of molecules, and in being able to explain how the structure of the constituent molecules or atoms relates to the macroscopic properties of materials. Be aware that the shells reflect the quantization inherent in quantum mechanics and that the labels given to the atomic orbitals are examples of the quantum numbers used to label the resulting quantized states. Being aware of the quantum mechanical model as the currently accepted best model for the atom is important for scientific literacy.

Essential knowledge 1.C.1: many properties of atoms exhibit periodic trends  that are reflective of the periodicity  of electronic structure.

  1. The structure of the periodic table is a consequence of the pattern of electron configurations and the presence of shells (and subshells) of electrons in atoms.
  2.  Ignoring the few exceptions, the electron configuration for an atom can be deduced from the element’s position in the periodic table.
    Memorization of exceptions to the Aufbau principle is beyond the scope of this course land the AP Exam.
  3. For many atomic properties, trends within the periodic table (and relative values for different atoms and ions) can be qualitatively understood and explained using Coulomb’s Law, the shell model, and the concept of shielding/effective nuclear charge. These properties include:
    • First ionization energy
    • Atomic and ionic radii
    • Electronegativity
    • Typical ionic charges
  4. Periodicity is a useful tool when designing new molecules or materials, since replacing an element of one group with another of the same group may lead to a new substance with similar properties. For instance, since SiO2 can be a ceramic, SnO2 may be as well.

Learning Objectives:
LO 1.8 The student is able to explain the distribution of electrons using Coulomb’s Law to analyze measured energies.

LO 1.9 Be able to predict and/or justify trends in atomic properties based on location on the periodic table and/or the shell model. [See SP 6.4]
LO 1.10 Justify with evidence the arrangement of the periodic table and apply periodic properties to chemical reactivity. [See SP 6.1]
LO 1.11 Analyze data, based on periodicity and the properties of binary compounds, to identify patterns and generate hypotheses related to the molecular design of compounds for which data are not supplied. [See SP 3.1, 5.1]

LO 2.14 The student is able to apply Coulomb’s Law qualitatively (including using representations) to describe the interactions of ions, and the attractions between ions and solvents to explain the factors that contribute to the solubility of ionic compounds.

Learning Targets Ch. 8.1 Development of the Modern Periodic Table
Review Questions 8.1-8.4; problems 8.18-8.32

Students will know....

  • the principles Mendeleev used to arrange the periodic table
  • how Mendeleev's table allowed for and predicted properties of some elements not yet known.

Students will be able to....

  • Explain the basis of the periodic table as described by Mendeleev and Meyer and indicate the shortcomings of their method.
  • Explain the basis of the periodic table as described by Moseley and how it predicted properties of “missing” elements.
Learning Targets Ch. 8.2 Periodic classification of the Elements
Review Questions 8.5-8.17; problems 8.18-8.32

Students will know....

  • Terms: core electrons, valence electron, representative elements, transition elements, paramagnetic, diamagnetic, isoelectric
  • The outermost electrons and in which type of subshell and orbital they reside determines their chemical reactivity
  • elements that correspond to each of the following groups:
    • representative elements
    • noble gases
    • transition metals
    • lanthanides
    • actinides
  • electron configuration of cations and anions and identity ions and atoms that are isoelectronic.

Students will be able to....

  • Divide elements into groups based on the type of outermost subshell being filled
  • Classify the electron configuration of an element as paramagnetic or diamagnetic
  • Write electron configurations using the building-up principal OR the location of an element on the periodic table
  • Write electron configurations for ions
  • Identify isoelectric species
Learning Targets Ch. 8.3 Periodic Variation in Physical Properties
Review Questions 8.33-8.36; Problems 8.37-8.48

Students will know....

  • Shielding effect
  • The property of effective nuclear charge and its impact on physical and chemical properties
  • Atomic radius
  • Ionic radius

Students will be able to....

  • Apply the concept of effective nuclear charge and shielding constants (screening constants) to justify why the first ionization energy is always smaller than the second ionization energy of a given atom.
  • Predict the trends from left to right and top to bottom of the periodic table for each of the following:
    • atomic radius
    • ionic radius
Learning Targets Ch. 8.4 Ionization Energy
Review Questions 8.49-8.50; Problems 8.51-8.58

Students will know....

  • ionization energy

Students will be able to....

  • Predict the trends from left to right and top to bottom of the periodic table for ionization energy
Learning Targets Ch. 8.5 Electron Affinity
Review Questions 8.59-8.60; Problems 8.61-8.64

Students will know....

  • electron affinity

Students will be able to....

  • Predict the trends from left to right and top to bottom of the periodic table for electron affinity
Learning Targets Ch. 8.6 Variation in Chemical Properties of the Representative Elements
Review Questions 8.65-8.66; Problems 8.67-8.74

Students will know....

  • why hydrogen could be placed in a class by itself when reviewing its chemical properties.
  • examples of Group 1A elements reacting with oxygen to form oxides, peroxides, and superoxides.
  • the reactivity of alkaline earth metals with water.
  • how strontium-90 could lead to human illness.
  • the metals, nonmetal, and metalloids of Group 4A.
  • the halides (halogens)
  • the three hydrohalic acids that are strong acids and the one hydrohalic acid that is a weak acid.
  • why the name for Group 8A has changed from inert gases to noble gases.
  • List the three “coinage” metals and explain their relative inertness.

Students will be able to....

  • Predict the trends from left to right and top to bottom of the periodic table for metallic character
  • Predict the reaction of alkali metals with water.
  • Compare the reactivity of boron, a metalloid, to aluminum.
  • Write equations for the reactions that form nitric acid, phosphoric acid and sulfuric acid.
  • Rationalize the characteristics of the properties of oxides of the third period elements.
  • Classify oxides as acidic, basic, or amphoteric.
  • Explain why concentrated bases such as NaOH should not be stored in glass containers
Daily Learning Activities
Day 29
  • Periodic Trends: review of Periodic Table and Periodic Trends POGILS
Day 30
  • Physical and Chemical properties of groups (families) according to this Google doc. Share your work on this spreadsheet. This website will likely be helpful.
    Assignment: Use the spreadsheet created in class and the references to write an analysis of trends across periods for physical and chemical properties. Discuss at least 1 exception to each.

Links and Resources

Textbook, Chapter 8 - all sections.
Development of the periodic table- ppt from 1st year chemistry as review
Inorganic Chemistry website - thank you, Glen Shafer
Writing good responses to AP questions on periodicity - from Adrian Dingle

© L. C. Lee 1990-2013
Creative Commons License
This work by Luann Christensen Lee is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
Based on a work at www.chemistar.com.

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