14 Alkali Metals Group 1 (Except H) All have only 1 valence electron Most reactive metals; never found in elemental form in natureSoft and shinyRelatively low melting points
15 Alkaline Earth Metals Group 2 All have 2 valence electrons Second most reactive metals; never found in pure state in natureHarder, denser, and stronger than alkali metalsHave higher melting points than alkali metals
16 Transition Metals Groups 3-12 All have 1 or 2 valence electrons (in s sublevels)Do not fit into any other group or familyHave many irregularities in their electron configurations
17 Boron Family Group 3A Have 3 valence electrons Boron is a metalloid All others are metals
18 Carbon Family Group 4A All have 4 valence electrons Carbon is a nonmetalSi and Ge are metalloidsSn and Pb are metals
19 Nitrogen Family Group 5A All have 5 valence electrons (s and p sublevels)N and P are nonmetalsAs and Sb are metalloidsBi is a metal
20 Oxygen Family Group 6A All have 6 valence electrons Oxygen, Sulfur, and Selenium are nonmetalsTellurium and Polonium are metalloids
21 Halogens Means “salt former” Group 7A All have 7 valence electrons Most reactive nonmetalsAll are nonmetals
22 Noble GasesGroup 8A8 Valence electrons makes a full electron shell: s2 p6Complete, stable electron configuration (Complete outer energy level)Least reactive of all elements
23 Rare Earth Elements (Inner Transition metals) Found in 2 rows at bottom of periodic tableLanthanide series follows LaActinide series follows AcLittle variation in propertiesActinides are radioactive; only first three and Pu are found in nature
24 Summary Groups: Up and Down Periods: Across Main Group Elements are in groups 1-2, 13-18Elements along the stair step line are metalloidsElements to the left of the stair step line are metalsElements to the right of the stair step line are nonmetals
25 Octet Rule “Noble Gas Envy” Atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons (typically 8)
26 PeriodicityProperties of the elements change in a predictable way as you move through the periodic tableThese properties includeAtomic RadiusIonization energyElectronegativity
27 Atomic RadiusDistance from nucleus to outermost valence electrons
28 Atomic RadiusIncreases down groupsDecreases from left to right
29 Ionization Energy The energy needed to remove 1 of an atom’s electrons Decreases as you move down a groupIncreases from left to right, across a periodSuccessive ionization energies increase for every electron removed
31 ElectronegativityReflects an atom’s ability to attract electrons in a chemical bondRelated to its ionization energy and electron affinityIncreases from left to right, across a periodDecreases from top to bottom, down a group
33 ShieldingShielding electrons are electrons located between the nucleus and the valence electronsFor example:Chlorine has the following electron configuration:1s2 2s2 2p6 3s2 3p5The shielding electrons would be 1s2 2s2 2p6The valence electrons would be 3s2 3p5Then we have 10 shielding electrons and 7 valence electrons, right?
34 Shielding You try one Did you get: Try Sodium (Na)… Remember, first you have to know the electron configurationDid you get:Electron configuration: 1s2 2s2 2p6 3s1Shielding electrons: 1s2 2s2 2p6Valence electrons: 3s1So we have 10 shielding electrons and 1 valence electron, right?
35 ZeffEffective nuclear charge (Zeff) is the charge felt by the valence electrons after you’ve taken into account the number of shielding electrons that surround the nucleus.Huh?Let’s put it in an equation
36 Zeff =# of protons - # of shielding electrons So, calculate the effective nuclear charge for the all the elements in period 3Now, calculate the effective nuclear charge for all the elements in group 2What pattern do you see arising?
37 What is the correlation between Zeff and atomic radius What is the correlation between Zeff and atomic radius? (Remember opposite charges attract)The greater the Zeff the smaller the atomic radiusI’m still lost…..Greater effective nuclear charge means that the valence electrons are feeling a greater pull toward the nucleus, making the atom smaller in size
38 In summary…Effective nuclear charge can be used to predict trends in atomic radiusIncreases from left to right and decreases from top to bottomZeff = Z - σEffective nuclear charge is dependent upon electron shieldingElectronegativity increases from left to right and decreases from top to bottom