Unit 4: The Periodic Table and Periodic Trends (Periodicity) Chemistry

atomic number Background on the Periodic Table Dmitri Mendeleev: given credit for Periodic Table (~1870) -- organized Table by increasing atomic mass left spaces and predicted properties of undiscovered elements put elements in order of increasing ______________. Mendeleev

Regions of the Table metals: left side of Table(1-3 valence e-); form cations properties: lustrous (shiny) ductile (can pull into wire) malleable (can hammer into shape) good conductors (heat and electricity) hard

nonmetals: right side of Table(5-7 valence e- ; form anions by gaining electrons properties: good insulators, poor conductors gases or brittle solids dull Regions of the Table (cont.) Br 2 I2I2 S8S8 Ne bromineiodinesulfurneon

computer chips metalloids (semimetals): “stair” between metals and nonmetals properties: (intermediate)in-between those of metals and nonmetals; “semiconductors” Regions of the Table (cont.) (B, Si, Ge, As, Sb, Te, At) Si and Ge computer chips metals nonmetals

Periodicity there are trends in properties of elements -- left-right AND up-down trends atomic radius: the size of a neutral atom add a new energy level each time WHY? …increases as we go …decreases as we go WHY? Increase in nuclear charge it has to do with…

Atomic Radii Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B IA IIA IIIA IVA VA VIA VIIA = 1 Angstrom

ionic radius: cationsanions Ca atomCa 2+ ion Cl atom Cl 1– ion the size of an ion 20 p + 20 e – 20 p + 18 e – 17 p + 17 e – 17 p + 18 e – Ca Ca 2+ Cl Cl 1– cations lose electrons- smaller Anions gain electrons larger

IA IIA IIIA IVA VA VIA VIIA Li 1+ Be 2+ Na 1+ Mg 2+ Cl 1- N 3- O 2- F 1- S 2- Se 2- Br 1- Te 2- I 1- Al 3+ Ga 3+ In 3+ Tl 3+ Ca 2+ K 1+ Sr 2+ Rb 1+ Cs 1+ Ba 2+ Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba BeBCNOF = 1 Angstrom Atomic Radii Ionic Radii Cations: smaller than parent atoms Anions: LARGER than parent atoms

ionization energy: the energy required to remove an e – from an atom As we go, 1st I.E…. Nonmetals tend to gain therefore having a high first ionization energy. Metals tend to lose-low first ionization energy decreases. increases. (due to the shielding effect- increase in the number of energy levels) Each successive ionization requires more energy than the previous one.

electronegativity: the tendency for a bonded atom to attract e – to itself As we go, electronegativity… decreases. increases. electronegativity increases Nonmetals tend to gain therefore having a high electronegativity. Metals tend to lose-low electronegativity

Reactivity of Metals Increases down a column –Reasons: Size (value of n), low ionization energy, and the shielding effect Decreases left to right across a period –Reasons: Stronger nuclear charge and Increase in ionization energy

Reactivity of Nonmetals Increases left to right across a period –Why? Smaller in size Stronger nuclear charge Increased ionization energy Decreases down a column –Why? Decreased electronegativity Larger in size

Reactivity Overview Fr-most reactive metal F-most reactive nonmetal Exception: Elements with half- filled sublevels are more stable than those with empty orbitals