Chapter 7: Periodic Properties of the Elements

7.1: Development of the Periodic Table

• elements in the same group/column usually have similar chemical properties
• however they are not identical
• Mendeleev and Meyer arranged elements according to atomic weight
• left holes for undiscovered elements
• Moseley rearranged the table later by atomic number
• Periodic trends include: size of atoms, ionization energy, and electron affinity

7.2: Effective Nuclear Charge

• electrons are attracted to the nucleus and repelled by other electrons in a many electron atom
• nuclear charge depends on both factors
• effective nuclear charge increases across row and down column

7.3: Size of Atoms

• bonding atomic radii defined as half the distance between covalently bonded nuclei
• increases right to left and top to bottom
• ionic size depends on nuclear charge, number of electrons, and the orbitals the electrons are located in
• cations (+) are smaller and their outermost electron is removed and repulsions are reduced
• anions (-) are larger and electrons are added and repulsions are increased
• ions increase in size as you go down a column due to increasing n value
• isoelectronic series ions have the same number of electrons
• ionic size decreases with an increasing nuclear charge

7.4: Ionization Energy

• amount of energy required to remove an electron ground its ground state
• first ionization energy removes first electron
• second for second.....
• requires more energy to move each electron
• when valence electrons have been removed, ionization energy takes a quantum leap
• increases going across left to right and up

7.5: Electron Affinity

• energy change accompanying addition of electron to gaseous ion
• becomes more exothermic going left to right usually
• increases going left to right across- does not always follow

7.6: Metals, Nonmetals, and Metalloids

• metals tend to create cations
• nonmetals tend to create anions
• metals- lustrous, malleable, ductile, good conductors
• metals and nonmetals as compounds tend to be ionic
• nonmetals- dull, brittle, bad conductors
• nonmetals tend to gain electrons to acquire noble gas electron configuration
• nonmetal substance is molecular compound
• most nonmetal oxides are acidic
• metalloids carry both metal and nonmetal characteristics

7.7: Group Trends for Active Metals

• Alkali Metals:
• soft, metallic metals
• only found as compounds
• low ionization energies
• reacts with water exothermically
• all but Li react with oxygen
• K, Rb, and Cs form superoxides
• produces bright colored flames
• Alkaline Earth Metals:
• high density and melting point
• low ionization energy but no as low as Alkalis
• doesn't react with water usually
• reactivity goes up as you go down the column

7.8: Group Trends for Selected Nonmetals

• Halogens:
• F, Cl, Br, I
• large, negative electron affinities
• oxidizes easily and reacts with metals to form halides
• Noble Gases:
• huge electron affinities
• He, Ne, Ar, Kr, Xe, Ra
• Oxygen:
• 2 allotropes: O3 and O2
• 3 anions: O^2-, O2^2-, O2^-
• tends to take electrons away- oxidation
• Sulfur:
• weaker oxidizing agent
• most stable allotrope is S8