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Chapter 6. Chemical & Physical Properties of the Elements and the Periodic Table. Review Quiz Chapter 6. Heats of (kJ/mol) conversion. ∆H summation formula. Valence Electrons. The valence electrons are the electrons in the outer energy level ( valence level ). Alkali Metals.
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Chapter 6 Chemical & Physical Properties of the Elements and the Periodic Table
Review Quiz Chapter 6 • Heats of (kJ/mol) conversion. • ∆H summation formula.
Valence Electrons • The valence electrons are the electrons in the outer energy level (valence level).
Alkaline Earth Metals
Inner Transition Elements (Metals)
Covalent radius • Covalent radius is essentially the size of an atom.
Covalent Radii (atomic radii) Atomic Radius
Ionic Radius • Ionic Radius is the size of an ion.
Isoelectronic Series • Substances are isoelectronic if they have the same electron configuration. • Name two isoelectronic species.
Ionization Energy • Ionization energy is the energy needed to remove an electron from an atom or ion.
First Ionization Energy • First Ionization energy is the energy needed to remove the first electron from an atom.
Multiple Ionization Energies • Second Ionization energy is the energy needed to remove the second electron from an atom. • Third Ionization energy is the energy needed to remove the third electron from an atom. • Etc.
Ionization Energies in kJ/mol Write the equation representing the first ionization energy of hydrogen.
First Ionization Energy of H • H + 1312 kJ → H+ + e-
Electron Affinity • The energy change that occurs when an electron is added to an atom.
Write the equation representing the electron affinity of hydrogen.
Electron Affinity of H • H + e-→ H- + 72 kJ
Effective Nuclear Charge (Zeff) • You will find many of the notes for effective nuclear charge on a sheet in your notebook titled “Effective Nuclear Charge”. • The effective nuclear charge (Zeff) of an atom is basically how well it is able to hold on to its most loosely held electron.
Effective Nuclear Charge (Zeff) • We can estimate the effective nuclear charge of an atom by using the following: • The nuclear charge (Z) • The shielding effect • Electron repulsions
The Nuclear Charge (Z) • Based on the number of protons in the nucleus. • Example: Carbon vs. Nitrogen
The greater the number of protons in the nucleus the greater the effective nuclear charge.
Shielding Effect. • The shielding effect is when electrons between the nucleus and the outermost electrons in an atom shield or lessen the hold of the nucleus on the outermost electrons.
Shielding Effect. • Shielding can be checked by writing the electron configuration.
Example of the Shielding Effect He atom in the excited state with one electron in the 1s and one electron in the 2p. He+ ion in the excited state with one electron in the 2p. 1s12p1 2p1
Shielding EffectEnergy Levels vs. Sublevels • Energy levels have the greatest effect on shielding. • Sublevels increase shielding but to a far lesser extent.
Effective Nuclear Charge can be used to help explain atomic radius. Atomic Radius
Explain the difference in atomic radii for Li and Be. Which are 1.52 and 1.11 angstroms respectively.
Explain the difference in atomic radii for Li and Na. Which are 1.52 and 1.86 angstroms respectively.
Effective Nuclear Charge can be used to help explain atomic radius. • Based on nuclear charge and shielding.
Electron Repulsions:Paired vs. Unpaired Electrons • A paired electron has increased electron – electron repulsion. • It is easier (takes less energy) to remove a paired electron than it does to remove an unpaired electron. • We check the pairing of electrons in the outer sublevel by writing an orbital filling diagram.
It is much harder to remove an electron from helium than it is Li. This is Illustrated by their respective ionization energies given below. Explain. • He = 2370 kJ/mol • Li = 520 kJ/mol Stability Schmability
Penetration Effect • Electrons in a higher energy level can often penetrate (dive) through lower energy levels because of the attraction that the nucleus has on them. • Smaller sublevels can penetrate closer to the nucleus than larger sublevels.