Chapter 8 - Periodic Relationships Among the Elements

8.1 - Development of the Periodic Table

• Henry Moseley, an English physicist, found a link between atomic number and the frequency of X rays produced by bombarding an element with high-energy electrons.

8.2 - Periodic Classification of the Elements

• The valence electrons, which are the outermost electrons, play a big role in the chemical reactivity of the elements.
• The term "core electrons” refers to all nonvalence electrons in an atom.

8.3 - Periodic Variation in Physical Properties

• When both the real nuclear charge (Z) and the repulsive effects (shielding) of the other electrons are taken into account
  • The effective nuclear charge (Zeff) is the nuclear charge felt by an electron.
• When we need to be even more precise, we use the atomic radius, which is half the distance between the two nuclei in two nearby metal atoms or a diatomic molecule.
• The radius of a cation or anion is called the ionic radius.
  • X-ray diffraction can be used to determine it.

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8.4 - Ionization Energy

• The minimum energy (in kJ/mol) necessary to remove an electron from a gaseous atom in its ground state is known as ionization energy (IE).

8.5 - Electron Affinity

• The ability of atoms to receive one or more electrons is another feature that has a significant impact on their chemical behavior.
  • The negative of the energy shift that occurs when an electron is received by an atom in the gaseous state to create an anion is called electron affinity (EA).

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8.6 - Variation in Chemical Properties of the Representative Elements

• Within a group, the metallic nature of the elements reduces from left to right over time and increases from top to bottom.
• Similarities between pairs of elements in various groups and periods of the periodic table are known as diagonal relationships.
• Most oxides can be classed as acidic or basic based on whether they form acids or bases when dissolved in water or if they react as acids or bases in specific processes.
  • Some oxides are amphoteric, meaning they have both acidic and basic characteristics. Na2O and MgO, the first two oxides of the third period, are basic.

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