Periodic Characteristics Valence electrons determine chemical & physical properties of the elements Valence electrons – the electrons in the outermost energy level Elements with the same number of valence electrons will have similar chemical properties. Metals have shared properties because they lose electrons Nonmetals have shared properties because they gain electrons

Periodic Characteristics Ion – an atom that either loses or gains electrons Metals tend to lose their valence electrons. Losing electrons(negative charges) makes them positive Cation – a positive ion Nonmetals tend to gain electrons Gaining electrons makes them negative Anion – a negative ion Ca ion + a negative ion

Periodic Table Groups The number of valence electrons determine the physical and chemical properties of the groups Group 1: Alkali Metals - Has only 1 valence electron - The most reactive metals - Not found in nature in pure form. Always in compounds Videos: alkali metals in water 1

Periodic Table Groups Group 2: Alkaline Earth Metals(two words, Group 2) - Has 2 valence electrons - Still very reactive - Not found in nature in pure form. Always in compounds demo: magnesium & oxygen 2

Periodic Table Groups Groups 3 through 12: Transition Metals - Valence electrons vary - metals can form multiple cations (Cr 2+,Cr 3+,Cr 7+ ) - compounds are brightly colored - Group 11 is least reactive demo: colored compounds

Periodic Table Groups Group 14: aka Carbon Group - Has four valence electrons - carbon has three allotropes: coal, diamond, graphite - Allotrope: substances made from the same element, but with different physical and chemical properties 1415 Group 15: Nitrogen Group - Has five valence electrons *note- bottom element is a metal!*

Periodic Table Groups  Group 16: Oxygen Group  6 valence electrons  oxygen has 2 allotropes:  O 2 (air) & O 3 (ozone)  Group 17: The Halogens  “salt-forming”  7 valence electrons  most reactive nonmetals  Most are diatomic(2 atoms): diatomic - compounds made with two atoms of the same element Other diatomic elements: Hydrogen, Oxygen & Nitrogen. - Together, they form BrINClHOF: Bromine(Br 2 ) Iodine(I 2 ), Nitrogen(N 2 ), Chlorine(Cl 2 ), Hydrogen(H 2 ), Oxygen(O 2 ), and Fluorine(F 2 )

Periodic Table Groups  Group 18: The Noble Gases - 8 valence electrons(except helium which has 2) - full outer shell (aka filled principal energy level) - chemically unreactive  Lanthanides  contain the rare earth metals  Many used in modern electronics  Actinides  some are man-made  all are radioactive & decay over time 18 Lanthanides → actinides →

Electron Configuration & The Periodic Table  Think back to electron configuration-  Electrons are arranged in energy levels  Energy levels are made up of orbitals: s, p, d & f  s can hold 2 electrons, p can hold 6, d holds 10, f holds 14  The Periodic Table can tell us what orbital is being filled by the atom's location on the Periodic Table.

P.T. & Electron Configuration The Periodic Table is sorted by the location of valence electrons in the electron configuration s-block : Electron configuration ends with s¹ or s² p-block : Electron configuration ends with p 1 through p 6 d-block : electron configuration ends with d 1 through d 10 Atoms in the d-block often form multiple cations. f-block: electron configuration ends with f 1 to f 14

Blocks s-block p- block d- block f-block

Average Isotopic Atomic Mass **The Atomic masses in the Periodic Table are not mass numbers. ** They are an average of all the isotopes of that element, weighted by abundance. · Rounding the ave. atomic mass in the P.T. usually gives you the most common isotope. For iron (mass amu in P.T.) the most common isotope is iron- _________ 56