Presentation on theme: "Periodic Table The most useful tool in the Lab. Early Organization J.W. Dobereiner (1829) organized elements in triads Triad – three elements with similar."— Presentation transcript:
Periodic Table The most useful tool in the Lab
Early 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 octaves Octave – repeating group of 8 elements
Development of the PeriodiceTable Dmitri Mendeleev taught chemistry in terms of properties. Mid 1800s - molar masses of elements were known. Wrote down the elements in order of increasing mass. Found a pattern of repeating properties.
Mendeleevs Table Grouped 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.
The Modern Periodic Table Henry Moseley – British physicist Arranged elements according to increasing atomic number The arrangement today Symbol, atomic number & mass
The 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) Werent found because they are unreactive.
Organization Horizontal rows = periods There are 7 periods Each period represents an energy level Every element in the same period has the same # of energy levels and the same core electron configuration
Organization Vertical column = group or family Similar physical & chemical prop. Same # of valence electrons Same common oxidation state Identified by number & letter
Horizontal rows are called periods There are 7 periods
Group 1A are the alkali metals Group 2A are the alkaline earth metals
Group 7A is called the Halogens Group 8A are the noble gases
The group B are called the transition elements u These are called the inner transition elements, and they belong here
1A 2A3A4A5A6A 7A 8A The elements in the A groups are called the representative elements outer s or p filling
Lanthanides – the 4f orbital fills for these elements
Actinide series – the 5f orbitals are being filled for these elements.
Types of elements Metals Non-metals Metalloids or semi-metals
Metals Good conductor of heat and electricity Malleable Ductile High tensile strength High luster Solid at room temperature React by losing electrons
Nonmetals Poor conductors of heat and electricity React by gaining electrons Some gases (O, N, Cl); some are brittle solids (S); one is a fuming dark red liquid (Br)
Semi-Metals Heavy, stair-step line Metalloids border the line Properties intermediate between metals and nonmetals Learn the general behavior and trends of the elements, instead of memorizing each element property B, Si, Ge, As, Sb, Te
Families Group IA – alkali metals most reactive metals Silvery in appearance Soft Combine easily with non-metals Melting point is higher than the boiling point of water Have 1 valence electron
Families Group 2 – Alkaline Earth Metal Family Harder, stronger, denser, higher melting point, and less reactive than alkali Usually not found as free elements, but as compounds Have 2 valence electrons
Families Group 7 – Halogens Most reactive family Non-metals Have seven valence electrons Group 8 – Noble Gas Inert, unreactive Have full set of valence electrons
Each row (or period) is the energy level for s and p orbitals
Areas of the periodic table Group A elements = s & p blocks representative elements Wide range of phys & chem prop.
Transition Metals -d block d1d1 d2d2 d3d3 s1d5s1d5 d5d5 d6d6 d7d7 d8d8 s 1 d 10 d 10
d orbitals fill up after previous energy level, so first d is 3d even though its in row d
F - block inner transition elements
f orbitals start filling at 4f f 5f
Atomic Size First problem: Where do you start measuring from? The electron cloud doesnt have a definite edge. Atomic Radius = half the distance between two nuclei of a diatomic molecule. } Radius
Trends in Atomic Size Influenced by three factors: 1. Energy Level Higher energy level is further away. 2. Charge on nucleus More charge pulls electrons in closer. 3. Shielding effect (blocking effect)
WHAT HAPPENS TO ATOMIC RADII? Does a negative ion (anion) get larger or smaller? Does a positive ion (cation) get larger or smaller?
Trends 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.
Ionic 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.
WHAT IS IONIZATION ENERGY? The energy required to remove an electron Which element has the highest ionization energy? Why?
What determines Ionization Energy? The greater the nuclear charge, the greater IE. Greater distance from nucleus decreases IE All the atoms in the same period have the same energy level. But, increasing nuclear charge So IE generally increases from left to right.
Ionization Energy The energy required to remove the first electron is called the first ionization energy The 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.
Driving Force Full Energy Levels require lots of energy to remove their electrons. Noble Gases have full orbitals. Atoms behave in ways to achieve noble gas configuration.
WHAT IS ELECTRONEGATIVITY?ELECTRONEGATIVITY The ability of an atom to pull off an electron. Which element has the highest electronegativity? Why?
Periodic Trend Metals are at the left of the table. They let their electrons go easily Low electronegativity At the right end are the nonmetals. They want more electrons. Try to take them away from others High electronegativity.
Trends 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.