TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity,Atomic and ionization energRadiusy. The atomic radius is the distance between the center of an atom’s nucleus and the electrons in its highest energy level. For diatomic elements, the atomic radius of an element is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined. • Atomic radii are often measured in picometers (pm). TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy. Atomic Radius (pm) 300
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0 0 10 20 30 40 50 60 70 80 90 Atomic Radius TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and Summary:ionic radii, electronegativity, trends and ionization energ iny. atomic radius TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionizationWhy? energy. Nuclear Charge (Z): Protons in the nucleus attract electrons. The more protons you have, the more attraction. Effective Nuclear Charge (Zeff ) accounts for the shielding effect. Distance: The farther away the electrons are from the nucleus, the less attracted they will be to the protons in the nucleus.
Shielding: Electrons in the lower energy levels shield or protect the electrons in the higher energy levels from the attraction of the protons in the nucleus. TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and Explanationionic radii, electronegativity, for and Trends ionization energy. in atomic radius
Atomic radius increases from top to bottom within a group because: • There is bigger distance between the protons in the nucleus and the outer electrons, decreasing the attraction forces according to Coulomb’s Law. • There is a shielding effect where the inner electrons shield the outer electrons, decreasing the attraction between them (Zeff is constant). Atomic radius decreases across a period because:
• The effective nuclear charge (Zeff ) increases with an increase in the number of protons in the nucleaus (shielding is constant) TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy. Different types of Ions: Cations (+) and Anions (-)
Ion is any atom with a charge. During reactions between metals and nonmetals, metal atoms tend to lose electrons and nonmetal atoms tend to gain electrons. • Cations (metals) have a positive charge. • Anions (nonmetals) have a negative charge. TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy. Ionic Radius 250
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Ionic Radius TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity,Ionic and and ionization Atomic energy. Radius 250
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0 0 5 10 15 20 Atomic Radius Ionic Radius TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and Groupionic radii, trends electronegativity, inand ionization ionic energy. radius: Cations
• When an atom loses an electron, the attraction between the remaining electrons and the nucleus is increased. • As a result, the electrons are drawn closer to the nucleus. • Metals that are representative elements tend to lose all their outermost electrons during ionization—the ion has one fewer occupied energy level. • Cations are smaller than their original atoms. TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and Groupionic radii, trends electronegativity, inand ionization ionic energy. radius: Anions
• As the number of electrons increases, the attraction of the nucleus for any one electron decreases. • As the number of electrons increases, there is more electron-electron repulsion. • Anions are larger than their original atoms. TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy. Summary: trends in ionic radius TEKS 5C: Use the Periodic Table to identify and explain periodic trends, including atomic and Explanationionic radii, electronegativity, for and ionizationTrends energy. in ionic radius
Atomic radius increases from top to bottom within a group because: • There is bigger distance between the protons in the nucleus and the outer electrons, decreasing the attraction forces according to Coulomb’s Law. • There is a shielding effect where the inner electrons shield the outer electrons, decreasing the attraction between them (Zeff is constant). Atomic radius decreases across a period because:
• The effective nuclear charge (Zeff ) increases with an increase in the number of protons in the nucleaus (shielding is constant)