4 History of the Periodic Table By 1860 more than 60 elements had been discovered.Chemists learned about the new elements by reacting them with other elements to form new compounds.In 1865, John Newlands, an English chemist, arranged the known elements according to their properties in order of increasing atomic mass.The properties of elements seemed to repeat every eight elements. This pattern is known as the law of octaves.
5 History of the Periodic Table In 1869, Dmitri Mendeleev, a Russian chemist, used Newland’s observations and other observations to produce the first PERIODIC Table.He placed each element on a card with the element’s atomic mass, chemical and physical properties. He arranged the elements in many different ways according to various properties and looked for trends.When he arranged the elements according to increasing atomic mass, he noticed that certain similarities occurred at regular intervals. This was considered a “periodic pattern”.He arranged all the elements in a table according to increasing atomic mass, starting a new row every time the pattern repeated, and the elements with similar properties fell in the same vertical columns (with a few exceptions).He had some blank spaces in his table where he thought new elements would be discovered. These blank spaces were used to predict the existence and discovery of new elements.
6 History of the Periodic Table By 1886 three new elements were discovered that followed Mendeleev’s predication.Most chemists were persuaded to accept his table, labeling Mendeleev the founder of the periodic law.
7 History of the Periodic Table In order to keep the pattern of properties, Mendeleev had to switch some elements out of order based on atomic mass.In 1911, Henry Moseley, an English chemist, was examining the spectra of 38 different metals. He noticed that the wavelengths of spectra lines correlated to atomic numbers, not atomic mass.Moseley discovered a new pattern and organized the elements according to their increasing nuclear charge, or atomic number, i.e. increasing number of protons.When the elements were arranged by increasing atomic number, the discrepancies in Mendeleev’s table disappeared.
15 Do NowTake out your Reference Tables and open to the Periodic Table of ElementsWhat do you think of when you hear the word metal?What is a nonmetal?Do you know of any examples of each?
16 The Periodic Table consists of: METALSNONMETALSMETALLOIDS
17 Properties of MetalsMetals are good conductors of heat and electricityMetals are malleable (can be hammered or rolled into sheets)Metals are ductile (can be made into wire)Metals have high tensile strengthMetals have luster
18 Examples of MetalsPotassium, K reacts with water and must be stored in mineral oilCopper, Cu, is a relatively soft metal, and a very good electrical conductor.
19 Examples of Metals Zinc, Zn, is more stable than potassium Mercury, Hg, is the only metal that exists as a liquid at room temperature
20 Mixing metalsAlloy = mixture of a metal with another element, usually another metalAlloys have properties different from the individual elements, usually eliminating some disadvantages.Alloys are usually harder and more resistant to corrosionEx: brass = copper + zincEx: sterling sliver = copper + silverEx: steel = iron + carbon + manganese + nickelEx: Stainless steel = iron + chromium
21 Properties of Nonmetals Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.Nonmetals are poor conductors of heat and electricityNonmetals tend to be brittleMany nonmetals are gases at room temperature
22 Examples of Nonmetals Sulfur, S, was once known as “brimstone” Microspheres of phosphorus, P, a reactive nonmetal
23 Examples of NonmetalsGraphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structureBromine is a nonmetal that exists as a liquid at room temperature.
24 Properties of Metalloids Metalloids straddle the border between metals and nonmetals on the periodic table.They have properties of both metals and nonmetals.Metalloids are more brittle than metals, less brittle than most nonmetallic solidsMetalloids are semiconductors of electricitySome metalloids possess metallic luster*note them on your Periodic Table in your Reference Table!
25 Silicon, Si – A Metalloid Silicon has metallic lusterSilicon is brittle like a nonmetalSilicon is a semiconductor of electricityOther metalloids include:Boron, BGermanium, GeArsenic, AsAntimony, SbTellurium, Te
28 Do NowTake out your Reference Table and open to the Periodic Table of ElementsDo you notice any patterns as you look at the properties of elements?Hints: scan left to right, and scan from the top down
29 The Periodic Table PERIODIC LAW THE MODERN PERIODIC TABLE The physical and chemical properties of the elements are periodic functions of their atomic numbers (elements with similar properties appear at regular intervals).THE MODERN PERIODIC TABLEAn arrangement of the elements in order of increasing atomic number so that the elements with similar properties fall in the same column or group.
30 Periodic Table with Group Names PERIODS= horizontal rowsGROUPS= vertical columns
31 VALENCE ELECTRONSElements within the same group have the same number of valence electrons.
32 VALENCE ELECTRONSMost loosely bound electron is called the VALENCE ELECTRON!Valence electrons participate in chemical reactions, so elements with similar valence electrons react in similar ways.Noble gases are stable with _8_ valence electrons.All elements with the exception of Hydrogen and Helium want _8_ valence electrons to be stable.Hydrogen and Helium want _2_ valence electrons to be stable.
35 s-BLOCK and p-BLOCK are considered “MAIN GROUP ELEMENTS” s-Block: Includes GROUP 1 and GROUP 2GROUP 1 - Alkali MetalsGROUP 2 – Alkaline Earth Metalsp-Block: Elements vary greatly in properties, includes GROUP 13 through GROUP 18GROUP 17 – HalogensGROUP 18 – Noble Gases
36 GROUP 1 Alkali Metals Properties: Metal Easily lose valence electron Chemically reactive – do not occur as free elements in natureSoft, silveryGood conductor of electricityReact violently with waterReact with halogens to form salts
37 EXCEPTION: Hydrogen is in group 1, but has different properties than the alkali metals *note that Hydrogen is a nonmetal on your Periodic Table in your Reference Table!
38 Hydrogen Most common element in the universe. It consists of one proton and one electron.It can react with many other elements:With oxygen to make waterWith carbon to make organic compoundsWith nitrogen to make ammonia
39 GROUP 2 Alkaline Earth Metals Properties:They are metals, but have less metallic characteristics than Alkali Metals2 valence electronsChemically reactive – do not occur as free elements in natureHarder, denser, stronger, higher boiling points, and slightly less reactive than alkali metals
40 Group 13 Properties: 3 valence electrons Lose 3 electrons to form 3+ ionsBoron is a metalloid and does not form a 3+ ion readily
41 Group 14 Properties: 4 valence electrons Carbon is a nonmetal with two distinct crystalline forms known as allotropes (graphite and diamond)Silicon and Germanium are metalloids used in the computer industryTin and Lead are metals
42 Group 15 Properties: 5 valence electrons Nitrogen is a nonmetal that exists naturally as N2, a diatomic molecule with a triple bond.Phosphorus is a nonmetal that exists in two allotropic forms (red and white)
43 Group 16 Properties: 6 valence electrons Oxygen is a nonmetal that exists naturally in two allotropic forms (O2 and O3)Sulfur is a nonmetal that exists naturally in several allotropic formsSelenium is a nonmetalTellurium is a metalloidPolonium is a metal
44 GROUP 17 Halogens (“Salt makers”) Properties:Most reactive nonmetals.7 valence electrons – need 1 electron to become stableThey vigorously react with metals to form salts.F2 - most reactive elementCl2Br2I2Gases at STPLiquid at STPSolid at STP
45 GROUP 18 NOBLE GASES (or INERT GASES) Properties:Full set of valence electrons: most elements have 8 valence electrons, except Helium with 2 valence electrons, but it is still associated with this group because its properties match these elements.Extremely stable and occur as monoatomic gases in natureAlthough they do not readily combine with other elements, but compounds of Krypton and Xenon have been prepared.
46 Monoatomic Atoms All of the noble/inert gases are monatomic. Monatomic means one atom.
47 Magic seven*note them on your Periodic Table in your Reference Table!Diatomic molecules= always exist as 2 of the same atoms bonded to each otherH2N2O2F2Cl2Br2I2
48 Transition Metals (d-Block) They have “typical metallic properties”Luster, ductile, malleable, good conductors of heat and electricityLess reactive than Group 1 and 2Many are unreactive (for example, palladium, platinum and gold are found as pure elements in nature)These elements begin in Period 4 and include Groups 3-12.
49 Transition Metals (d-Block) As ions, the transition elements form colorful solutions.
50 Lanthanides and Actinides (f-Block) Lanthanide Series- shiny metals similar in reactivity to Alkaline Earth MetalsActinides Series- all radioactive (mostly synthetic)
51 Synthetic Elements Synthetic elements do not occur in nature Ex: Technetium (Tc): atomic number 43Ex: All elements with atomic numbers > 92 (transuranium elements), which are all radioactiveThese elements are produced artificially by bombardment or as by-products of fission reactors.
53 What did you learn today? The placement or location of elements on the Periodic Table gives an indication of physical and chemical properties of that element. The elements on the Periodic Table are arranged in order of increasing atomic number.The number of protons in an atom (atomic number) identifies the element. The sum of the protons and neutrons in an atom (mass number) identifies an isotope.Elements can be classified by their properties and located on the Periodic Table as metals, nonmetals, metalloids (B, Si, Ge, As, Sb, Te), and noble gases.Elements can be differentiated by their physical properties. Physical properties of substances, such as density, conductivity, malleability, solubility, and hardness, differ among elements.Elements can be differentiated by chemical properties. Chemical properties describe how an element behaves during a chemical reaction.For Groups 1, 2, and on the Periodic Table, elements within the same group have the same number of valence electrons (helium is an exception) and therefore similar chemical properties.
58 The trend depends on 3 factors: NUCLEAR CHARGE= atomic number= # of protons- the higher the nuclear charge the more the electrons are pulled toward the nucleus.PRINCIPAL ENERGY LEVEL- Principal energy level is determined by the period an atom is located; the higher the principal energy level, the higher the potential energy, the larger the atom.ELECTRON CLOUD SHIELDING EFFECT- inner electrons shield the outer electrons so they are less attracted to the nucleus so the atom is larger
59 ElectronegativityA measure of the ability of an atom in a chemical compound to attract electrons.FLUORINE is the most electronegative atom on the Periodic TablePERIOD TREND: Electronegativity increases across a period(the closer to 8 valence electrons the more they will pull on the electrons)GROUP TREND: Electronegativity decreases down a group(the larger the atomic radius the less ability of that atom to attract electrons due to electron shielding)
62 Electronegativity Review Element with most Electronegativity:Element with least Electronegativity:
63 Atomic Radius PERIOD TREND: Radius decreases across a period Atomic radius = half of the distance between nuclei of identical atoms bonded together (bond radius).This is determined by how strongly an atom’s nucleus (positive charge) is attracted to its outermost electrons.PERIOD TREND: Radius decreases across a periodNuclear charge increases across a period so electrons are more closely attracted to the nucleusGROUP TREND: Radius increases down a groupAddition of principal energy levels, so inner electrons shield outer electrons and the electrons are farther away from nucleus, so atom is larger.
67 Review Ions Ions are formed when atoms gain or lose electrons Ions have a positive or negative chargeIonic Radii: The loss or gain of electrons by an atom causes a corresponding change in size.
68 Ionic Radii Cations Anions Positively charged ions Smaller than the corresponding atomMetal tend to form CATIONS by LOSING an electron.Metal cations are smaller than their corresponding neutral atoms (they lost electrons).Negatively charged ionsLarger than the corresponding atomNonmetals tend to for ANIONS by GAINING an electron.Nonmetal anions are larger than neutral atoms because they gained electrons.
69 Here is a simple way to remember a cation and an anion: This is a cat-ion.He’s a “plussy” cat!This is Ann Ion.She’s unhappy and negative.
71 Ionic Radius ReviewThe loss or gain of electrons by an atom causing a corresponding change in size.MetalsTend to ____ their valence electrons.What happens to their valence electrons?__________Before: After:Therefore the atomic radius of metals is ___________ than their ionic radius.
74 Ionic Radius ReviewThe loss or gain of electrons by an atom causing a corresponding change in size.NonmetalsTend to _________ electrons.What happens to their radius?__________Before: After:Therefore the atomic radius of nonmetals is ________________ than their ionic radius.
77 Ionic Radius Metals form CATIONS Loss of electron Get a Positive ChargeNonmetalsFormANIONSGain of electronGet a Negative chargeRadius Decreases when it becomes an ionRadius Increases when it becomes an ion
78 Do Now Period 2: Li Be C N O F Ne Which elements do not want to lose their electrons? ____________
79 A + ionization energy A+ + e- Ionization energy = the energy required to remove an electron from an atomA + ionization energy A+ + e-PERIOD TREND: Tends to increase across a periodWithin same principle energy level: due to increased nuclear charge the electrons are more closely attracted to nucleusGROUP TREND: Tends to decrease down a groupAddition of principle energy levels, so outer electrons are farther from the nucleus due to electron shielding, so less attracted to the nucleus
83 Ionization of Magnesium Ionization energy increases for successive electrons taken from the same atomMg kJ Mg+ + e-Mg kJ Mg e-Mg kJ Mg e-
84 Ionization Energy Review Element with the most Ionization Energy:Element with the least Ionization Energy:Why do noble gases have such high ionization energy but no electronegativity?
85 A + e- + energy A- (unstable) Electron AffinityThe energy change that occurs when an electron is acquired by a neutral atom is called the atom’s electron affinity.A + e- A- + energyA + e- + energy A- (unstable)PERIOD TREND: Tends to increases across a perioddue to increasing nuclear charge (remember: the Halogens gain electrons most readily)GROUP TREND: Tends to decrease down a groupdue to increasing electron shielding from addition of principle energy levels
86 REACTIVITY METALS- most reactive in lower left corner NONMETALS- most reactive in top right corner, but it does not include noble gases
93 Reactivity Review:Place the following elements in increasing order of reactivity: (least reactive first)Sodium, potassium, calciumGroup 1, Group 1, Group 2, so…Calcium, sodium, potassium
94 Metallic CharacterAs you go down a group, the metallic character increases.As you go across a period, the metallic character decreases.
95 Melting PointMelting points are the amount of energy required to break a bond(s) to change the solid phase of a substance to a liquid. The stronger the bond between the atoms of an element, the higher the energy requirement in breaking that bond.Metals generally possess a high melting point.Most nonmetals possess low melting points.
97 Boiling PointBoiling points are the amount of energy required to break a bond(s) to change the liquid phase of a substance to a gas.The stronger the bond between the atoms of an element, the higher the energy requirement in breaking that bond.Metals generally possess a high boiling point.Most nonmetals possess low boiling points.
99 Summation of Periodic Trends ElectronegativityElectronegativity
100 Periodic Trends Definition Trend in Period Trend in Group ElectronegativityThe measure of the ability of an atom in a chemical compound to attract electronsIncreases across a periodDecrease down a groupAtomic RadiusHalf the distance between nuclei of identical atoms bonded togetherDecreases across a periodIncreases down a groupIonization EnergyThe energy required to remove an electron from an atomDecreases down a group*Use Table S in your Reference Tables!