6Henry MoseleyDiscovered in 1914 that elements’ properties more closely followed their atomic numberModern Periodic Table based on this discovery
7Periodic LawPhysical and chemical properties of elements are periodic functions of atomic numbers
8Classification of the Elements Elements are organized into different blocks in the periodic table according to their electron configurations
9Organizing the Elements by Electron Configuration Electrons in the highest principal energy level are called valence electrons.All group 1 elements have one valence electron.
10Organizing the Elements by Electron Configuration The energy level of an element’s valence electrons indicates the period on the periodic table in which it is found.The number of valence electrons for elements in groups is ten less than their group number.
11Organizing the Elements by Electron Configuration
12What is periodicity?Properties of the elements change in a predictable way as you move through the periodic tableThese properties includeAtomic radiusOctet RuleIonic radiusIonization energyElectronegativity
13How are the elements organized? Periodic Table: a complete chart of all elements in the universeArranged according to physical and chemical propertiesEach box on the table contains the atomic number, atomic mass, and chemical symbol
14How are the elements organized? Groups: also known as families; are the columnsHave similar propertiesSome have specific names:Family 1: Alkali MetalsFamily 2: Alkaline Earth MetalsFamilies 3 – 12: Transition MetalsFamily 13: Boron Family
15How are the elements organized? Family 14: Carbon FamilyFamily 15: Nitrogen FamilyFamily 16: Oxygen FamilyFamily 17: Halogen FamilyFamily 18: Noble GasesPeriods: the rows on the periodic tableDo not have similar properties
25Alkali Metals Group 1 (except H) All have only 1 valence electron Most reactive metals; never found in pure state in natureSoft, shiny, have relatively low melting points
26Alkaline Earth Metals Group 2 All have 2 valence electrons Are the second most reactive metals; never found naturally in pure stateHarder, denser, stronger than alkali metalsHave higher melting points than alkali metals
27Transition 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
28Boron Family Group 13 Have 3 valence electrons Boron is a metalloid, while all of the others are metals
29Carbon Family Group 14 All have four valence electrons Carbon is a nonmetal; Si and Ge are metalloids; Sn and Pb are metals
30Nitrogen FamilyGroup 15All have 5 valence electrons (in s and p sublevels)N and P are nonmetals; As and Sb are metalloids; Bi is a metal
31Oxygen FamilyGroup 16All have 6 valence electrons (in s and p sublevels)All are nonmetals except Te, which is a metalloid, and Po, which is a metal.
32Halogens Means “salt former” Group 17 All have 7 valence electrons (in s and p sublevels)Most reactive nonmetalsAll are nonmetals except At, which is a metalloid
33Noble GasesGroup 18Complete, stable electron configuration (no valence electrons)Most unreactive elements
34Rare Earth Elements Found in 2 rows at bottom of Periodic Table Also known as the inner transition metalsLanthanide series: starts with LaActinide series: starts with AcLittle variation in propertiesActinides are radioactive; only first three and Pu are found in nature
35Periodic TrendsTrends among elements in the periodic table include their size and their ability to lose or attract electrons
36Atomic RadiusFor elements that occur as molecules, the atomic radius is half the distance between nuclei of identical atoms.
38Atomic RadiusAtomic radius generally increases as you move down a group.The outermost orbital size increases down a group, making the atom larger.
39Ionic RadiusAn ion is an atom or bonded group of atoms with a positive or negative charge.When atoms lose electrons and form positively charged ions, they always become smaller for two reasons:The loss of a valence electron can leave an empty outer orbital resulting in a small radius.Electrostatic repulsion decreases allowing the electrons to be pulled closer to the radius.
40Ionic RadiusWhen atoms gain electrons, they can become larger, because the addition of an electron increases electrostatic repulsion.
42Ionic RadiusThe ionic radii of positive ions generally decrease from left to right.The ionic radii of negative ions generally decrease from left to right, beginning with group 15 or 16.
43Ionization Energy The energy needed to remove one of its electrons Decreases as you move down a groupIncreases as you move across a periodSuccessive ionization energies increase for every electron removed
45Octet Rule (Rule of 8)Atoms tend to gain, share, or lose in order to acquire a full set of valence electrons (in most cases, this is 8)
46ElectronegativityReflects an atom’s ability to attract electrons in a chemical bondRelated to its ionization energy and electron affinityIncreases as you move across a periodIncreases as you move up a group