History of Periodic Table

Chapter 5

History 1860s – 60 elements discovered

– Cannizzaro - agreed on method to measure atomic mass

– Search for relationships between properties of elements

Dimitri Mendeleev Organized elements by increasing

atomic mass Noticed chemical and physical

properties followed trend, or pattern Periodic

Mendeleev’s Table

Henry Moseley Worked with Rutherford looking at line-

spectras Noticed better pattern when elements

were organized by increasing atomic # Periodic Law: the physical and

chemical properties of elements are periodic functions of their atomic #s

Regions of Periodic Table

Group Project

Main Group Elementss and p block elements

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 metals

Top: Lanthanide Series

Bottom: Actinide Series

Periodic Properties

Atomic Radii (Atomic Size) Def: half the distance between the

nuclei of identical atoms that are bonded together

}Radius

Atomic Radii - Group trends As we go down a

group Another energy

level… So the atoms get

bigger.

HLi

Na

K

Rb

Atomic Radii - Periodic Trends Go across a period the radius gets

smaller. Same energy level. More nuclear charge. Outermost electrons pulled in closer

Na Mg Al Si P S Cl Ar

Ionization Energy (IE) An e- can be removed from any atom if

there is enough energy

A + energy A+ + e-

Ion: atom or group of bonded atoms that has a (+) or(-) charge

Process that results in ion formed is ionization

Valence Electrons Def: The e- available to be lost, gained

or shared to form chemical compounds e- found in the outermost s and p

sublevels

Ionization Energy (IE) Def: the energy needed to remove one

e- from an atom (IE1 – first IE)

Atoms with HIGH ionization energy hold on tight to their electrons

IE – Group Trends

As you go down a group IE decreases Electron further away from nucleus Less attraction to nucleus, easier to

take e-

IE – Periodic Trends IE generally increases from left to right Increasing nuclear charge More nuclear charge holds on tight to e-

Exact opposite of atomic radius

IE2 and IE3

Energy required to remove additional e-

Energies keep getting higher and higher e- that are left are being held closer to

nucleus harder to remove Pg. 155

Ionic Radii (Ionic Size) Cation: positive ion

– Always smaller than atom– Lost e-, now nucleus pulling in more on

remaining e-s Anion: negative ion

– Always bigger than atom– Gaining e-, now e- are crowded and spread

out (repulsion of like charges)

Ionic Radii – Group Trends

Same as Atomic Radii More energy levels as go down size

increases

Ionic Radii – Periodic Trends

2 sections Metals on LEFT make CATIONs Nonmetals on RIGHT make ANIONS Cations (1A – 4A) Anions (5A – 8A)

– Decrease as go across (L-R) due to increase nuclear charge

Electronegativity Valance e- are involved in forming

bonds Some atoms in a chemical bond attract

the valance e- more than the other (tug of war)

Linus Pauling – electronegativity – measure of the ability of an atom in a chemical compound to attract e- from another atom in the compound

Electronegativity – Group Trends Tend to decrease down a group or

remain about the same Noble gases are NOT assigned

electronegativities

Electronegativity – Periodic Trends Tend to increase as you go across the

table F – most electronegative Fr – least electronegative