2 Early Periodic Table – Atomic Number In 1913 Henry Mosley discovered that each element contained a unique number of protons in the nucleiArranged elements in order of atomic number.Resulted in a clear periodic pattern of properties.
3 Periodic LawThere is a periodic repetition of chemical and physical properties of elements when arranged in increasing atomic number (increasing number of protons) called the periodic law
4 Representative Elements Modern Periodic TableOrganized in columns called groups or familiesRows are called periodsGroup A – representative elements (1A-8A)Group B - transition elements (1B-8B)Representative Elements(Group A)Representative Elements(Group A)Transition Elements(Group B)
5 Classification of Elements Three classifications for elements metals, nonmetals, and metalloids (semimetals).
6 Metals Properties of Metals shiny, smooth, solids (except mercury) Good conductors of heat and electricityHigh densitiesHigh melting and boiling pointsMalleable – bended or pounded into sheetsDuctile – drawn into wires
7 Groups of Metals Alkali metals – group 1A except H Alkaline earth metals – group 2AAlkali metals and alkaline earth metals are chemically reactiveTransition metals – group B elementsInner transition metalsLanthanideActinide
9 Organizing by Electron Configuration Group number for group A elements represents the number of valence electronsAtoms in the same group have similar chemical properties because they have the same number of valence electrons
10 Alkali Metals Electron configurations for alkali metals Lithium 1s22s [He]2s1Sodium s22s22p63s [Ne]3s1Potassium 1s22s22p63s23p64s [Ar]4s1Rubidium 1s22s22p63s23p64s23d104p65s1[Kr]5s1What do the four configurations have in common?They have a single electron in their outermost energy levelThey all have one valence electron, thus similar chemical properties
11 Alkaline Earth Metals Electron configuration for alkaline earth metals Beryllium [He]2s2Magnesium [Ne]3s2Calcium [Ar]4s2Strontium [Kr]5s2All alkaline earth metals have two valence electrons, thus similar chemical properties.
12 Question Time What are representative elements? What are Group B elements called?What are the three classifications for elements?What are the characteristics of metals?Where are the alkali metals and alkaline earth metals located?Where are transition metals located?What are the inner transition metals?How many valence electrons do alkali metals and alkaline earth metals have?
13 Nonmetals Gases or brittle, dull looking solids Poor conductors of heat and electricityUsually have lower densities, melting point, and boiling point than metals.Groups of nonmetalsHalogens 7ANoble gases 8Asulfur
15 Noble Gases Noble gases – Group 8A Called inert gases because they rarely take part in a reactionHe – 1s2Ne – 1s22s22p6Ar – 1s22s22p63s23p6Kr - 1s22s22p63s23p63d104s24p6Because noble gases have completely filled s and p sublevels, they do not react with other elements
16 Metalloids (Semimetals) Physical and chemical properties similar to both metals and nonmetalsThey are metallic-looking brittle solidsRelatively good electrical conductivity.Used in glasses, alloys, and semiconductorsThe six elements commonly recognized as metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Polonium and astatine are sometimes classified as metalloids
18 Question Time What are the properties of nonmetals? Where are halogens and noble gases found?Why are noble gases unreactive (inert)?What are the properties of metalloids (semimetals)?Which six elements are most commonly known as metalloids (semimetals)?