Periodicity. ! Sizes of atoms and ions. ! Ionization Energy! Electron affinity. ! Electronegativity! Metallic Character. Sizes of Atoms and Ions!

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Raymond Patterson
6 years ago
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1 Periodicity Sizes of Atoms and Ions!! Sizes of atoms and ions Atomic radii increase with increasing electron shielding.! Ionization Energy! Electron affinity Atomic radii decrease with increasing effective nuclear charge.! Electronegativity! Metallic Character 1 2

!!moving down a group, IE because of increased electron shielding.

2 Ion Size!Cations have radii than their neutral atoms. IONIZATION ENERGY Definition of Ionization energy (IE):!Anions have radii than their neutral atoms. Na(g)! Na + (g) + e - Ionization energy is always endothermic. What are the trends?!!moving down a group, IE because of increased electron shielding.!!moving across a row from left to right, IE because of increased effective nuclear charge. Is it easier to remove an electron from a 2p orbital or from a 2s orbital? 3 Is it easier to remove an electron if it is unpaired or paired? 4

Mg - (g) Definition of Electronegativity:!Due to decreasing atomic radius, electronegativity moving up a group on the periodic table.

3 ELECTRON AFFINITY Electron affinity: opposite of Electron affinity is the energy change when a gaseous atom an electron to form a gaseous ion: Cl(g) + e -! Cl - (g) Electron affinity can either be exothermic (as the above example) or endothermic: Mg(g) + e -! Mg - (g) Definition of Electronegativity:!Due to decreasing atomic radius, electronegativity moving up a group on the periodic table.!due to increasing nuclear charge, electronegativity moving across a period from left to right. Electron affinity generally in magnitude toward the top and the right on the periodic table. 5 6

4 METALS AND NONMETALS metals metalloids nonmetals Metals (75% of elements)!lustrous!(almost) all solids!malleable & ductile!good conductors of heat and electricity!oxides/hydroxides!aqueous cations (n+) Nonmetals!Non-lustrous, often colored!gases, liquids, & solids!solids are brittle!poor conductors of heat and electricity!oxides/hydroxides are!aqueous anions (n-) or oxyanions!reactivity downwards in family!reactivity downwards in family Metallic Character Metallic Character refers to the Properties of Metals: a) shiny or lustrous b) malleable and ductile c) oxides form basic ionic solids d) tend to form cations in aqueous solution Metallic character down a group. across a period. Metals have low ionization energies. Most neutral metals prefer to be oxidized (become more positive) rather than reduced. 7 8

5 Demonstrate Acid/Base Character of Oxides and Hydroxides Oxide + H 2 O! Hydroxide Element Oxide Hydroxide Acidic or Basic Na Na 2 O NaOH Mg (Ca) MgO Mg(OH) 2 Al Al 2 O 3 Al(OH) 3 Si SiO 2 Si(OH) 4 P P 2 O 5 PO(OH) 3 OXIDES and HYDROXIDES Metal Oxides and Hydroxides are more soluble in acidic solutions. More electropositive central atom gives off electrons (NaOH! Na + + OH - ) Non-Metal Oxides and Hydroxides are more soluble in basic solutions. More electronegative central atom attracts electrons (HNO 3! NO H + ) S SO 3 SO 2 (OH) 2 Cl Cl 2 O 7 ClO 3 (OH) 9 Metalloid Oxides and Hydroxides are More soluble in both acidic and basic solutions compared to pure water. 10

6 Metal reactivity Li Na K OXIDATION STATES Atoms tend to lose or gain electrons to achieve what kind of configuration? Elements to the right are electronegative gain electrons to become negatively charged anions or oxyanions. Elements to the left are electropositive lose electrons to become positively charged cations. NaCl! MgO!" For main group elements: The highest possible positive oxidation state is equal to the Group Number 11 12

7 DIAGONAL RELATIONSHIPS In many compounds, Li + resembles Mg 2 + rather than Na +. Examples: Li 2 CO 3 and MgCO 3 are virtually insoluble in water, while Na 2 CO 3 is very soluble. Ionic Radii: Li Å Be Na + Mg 2+ Al 0.95Å 0.65Å Be compounds are covalent and the hydroxide is amphoteric This behavior is similar to Al (example of a diagonal relationship) PERIOD II VS III Period II:!Small!The only valence orbitals are 2s and 2p No d orbitals Maximum number of bonds = 4. CF 4, NH 3.!Small size # a greater tendency to form $ bonds because there is better overlap of p-orbitals. Period III:! Bigger size.! Valence orbitals: 3s, 3p, and 3d. Maximum number of bonds > 4. SiF 4, SiF 6 2-, PCl 3, and PCl 5.!Bigger size # less tendency to form $ bonds because there is less overlap of p-orbitals

8 Bonding in Period II vs. III Multiple Bonds: elements past the second row are too big to allow good sidewise overlap of p-orbitals 15

Periodicity. Sizes of Atoms. Atomic radii increase with increasing electron shielding. Atomic radii decrease with increasing effective nuclear charge.

Periodicity. Sizes of Atoms. Atomic radii increase with increasing electron shielding. Atomic radii decrease with increasing effective nuclear charge. Periodicity! Sizes of atoms and ions! Ionization Energy! Electron affinity! Electronegativity! Metallic Character! Diagonal Relationships! Multiple Bonding 1 Sizes of Atoms Atomic radii increase with increasing