Presentation on theme: "The most useful tool in the Lab"— Presentation transcript:
1The most useful tool in the Lab Periodic TableThe most useful tool in the Lab
2Early Organization J.W. Dobereiner (1829) organized elements in triads Triad – three elements with similar properties (ex: Cl, Br, I)J.R. Newlands (1864) organized elements in octavesOctave – repeating group of 8 elements
3Development of the PeriodiceTable Dmitri Mendeleev taught chemistry in terms of properties.Mid 1800’s - molar masses of elements were known.Wrote down the elements in order of increasing mass.Found a pattern of repeating properties.
4Mendeleev’s TableGrouped elements in columns by similar properties in order of increasing atomic mass.Found some inconsistencies - felt that the properties were more important than the mass, so switched order.Also found gaps.Must be undiscovered elements.Predicted their properties before they were found.
5The Modern Periodic Table Henry Moseley – British physicistArranged elements according to increasing atomic numberThe arrangement todaySymbol, atomic number & mass
6The New Way Elements are still grouped by properties. Similar properties are in the same column.Order is by increasing atomic number.Added a column of elements (noble gases)Weren’t found because they are unreactive.
7Organization the same # of energy levels and Horizontal rows = periodsThere are 7 periodsEach period represents an energy levelEvery element in the same period hasthe same # of energy levels andthe same core electron configuration
8Organization Vertical column = group or family Similar physical & chemical prop.Same # of valence electronsSame common oxidation stateIdentified by number & letter
9Horizontal rows are called periods There are 7 periods
10Group 1A are the alkali metals Group 2A are the alkaline earth metals
11Group 7A is called the Halogens Group 8A are the noble gases
12The group B are called the transition elements These are called the inner transition elements, and they belong here
13The elements in the A groups are called the representative elements outer s or p filling1A8A2A3A4A5A6A7A
14Lanthanides – the 4f orbital fills for these elements
15Actinide series – the 5f orbitals are being filled for these elements.
16Types of elementsMetalsNon-metalsMetalloids or semi-metals
17Metals Good conductor of heat and electricity Malleable Ductile High tensile strengthHigh lusterSolid at room temperatureReact by losing electrons
18Nonmetals Poor conductors of heat and electricity React by gaining electronsSome gases (O, N, Cl); some are brittle solids (S); one is a fuming dark red liquid (Br)
19Semi-Metals Heavy, stair-step line Metalloids border the line Properties intermediate between metals and nonmetalsLearn the general behavior and trends of the elements, instead of memorizing each element propertyB, Si, Ge, As, Sb, Te
20Families Group IA – alkali metals most reactive metals Silvery in appearanceSoftCombine easily with non-metalsMelting point is higher than the boiling point of waterHave 1 valence electron
21Families Group 2 – Alkaline Earth Metal Family Harder, stronger, denser, higher melting point, and less reactive than alkaliUsually not found as free elements, but as compoundsHave 2 valence electrons
22Families Group 7 – Halogens Most reactive family Non-metals Have seven valence electronsGroup 8 – Noble GasInert, unreactiveHave full set of valence electrons
33} Atomic Size Radius First problem: Where do you start measuring from? The electron cloud doesn’t have a definite edge.Atomic Radius = half the distance between two nuclei of a diatomic molecule.
34Trends in Atomic Size Influenced by three factors: 1. Energy Level Higher energy level is further away.2. Charge on nucleusMore charge pulls electrons in closer.3. Shielding effect(blocking effect)
35WHAT HAPPENS TO ATOMIC RADII? Does a negative ion (anion) get larger or smaller?Does a positive ion (cation) get larger or smaller?
36Trends in Ionic Size Cations form by losing electrons. Cations are smaller than the atom they come from.Metals form cations.Cations of representative elements have noble gas configuration.
37Ionic size Anions form by gaining electrons. Anions are bigger than the atom they come from.Nonmetals form anions.Anions of representative elements have noble gas configuration.
38WHAT IS IONIZATION ENERGY? The energy required to remove an electronWhich element has the highest ionization energy? Why?
39What determines Ionization Energy? The greater the nuclear charge, the greater IE.Greater distance from nucleus decreases IEAll the atoms in the same period have the same energy level.But, increasing nuclear chargeSo IE generally increases from left to right.
40Ionization EnergyThe energy required to remove the first electron is called the first ionization energyThe second ionization energy is the energy required to remove the second electron.Always greater than first IE.The third IE is the energy required to remove a third electron.Greater than 1st or 2nd IE.
41Driving ForceFull Energy Levels require lots of energy to remove their electrons.Noble Gases have full orbitals.Atoms behave in ways to achieve noble gas configuration.
42WHAT IS ELECTRONEGATIVITY? The ability of an atom to pull off an electron.Which element has the highest electronegativity? Why?
43Periodic Trend Metals are at the left of the table. They let their electrons go easilyLow electronegativityAt the right end are the nonmetals.They want more electrons.Try to take them away from othersHigh electronegativity.
44Trends in Electron Affinity The energy change associated with adding an electron to a gaseous atom.Easiest to add to group 7A.Gets them to full energy level.Increase from left to right: atoms become smaller, with greater nuclear charge.Decrease as we go down a group.