 late 1790’s Antoine Lavoisier made a list of known elements ◦ contained 23 elements  1864 John Newlands looked further into organization ◦ The Law of Octaves – repeating trends every 8 elements

 Late 1800’s Russia  Grouped elements with similar properties into columns ◦ 7 columns were formed  Noble Gases (8 th Column) were later discovered  Was able to predict properties of missing elements  When Germanium was discovered, it fit his predictions

 Does mass always increase throughout the periodic table? ◦ NOPE  Tellurium (52)  Iodine (53)  Nickel (28)  Argon (18)  Potassium (19)

 The properties of the elements are a periodic function of their atomic masses ◦ periodic means repeating, like the moon cycle, every month it repeats  **atomic number was not known during Mendeleev’s time

 The properties of the elements are a periodic function of their atomic numbers  Using x-rays, Henry Moseley determined the number of protons per element ◦ This is Atomic Number  Elements with similar e- configurations are in the same columns known as “groups” or “families” ◦ Families  familiar characteristics ◦ Families have the same number of v.e.’s

 Rows are periods, each row designates a different nrg level  Columns are groups or families and contain elements with similar properties  Notable rows and columns ◦ Rows:  4f – Lanthanides  5f - Actinides ◦ Columns:  1 or IA – Alkali Metals  2 or IIA – Alkaline Earth Metals  17 or VIIA – Halogens  18 or VIIIA – Noble gases

 “A” Groups  Filling the ‘s’ and ‘p’ sublevels  Contains both metals and non metals

 “B” Groups  Fills the ‘d’ sublevels  Made up of only metals

 Fill the ‘f’ sublevels  Lanthanides  Actinides

 Luster (shine)  Ductile (pulled into wires)  Malleable (hammerable and won’t shatter)  Good conductors of heat and electricity  Have 3 or less v.e.’s so they tend to lose them ◦ Usually no more than 3 v.e.’s  Includes transition metals, actinides and lanthanides

 Brittle (most are gaseous)  Good insulators, not typically good conductors of heat or electricity  Have 5 or more v.e.’s, so they tend to gain (or share) e-’s

 Elements with properties of both metals and nonmetals  Located on the diagonal between metals and nonmetals  There are 8 metalloids  Can lose or gain v.e.’s depending on their placement on the periodic table

 8 e- in the outer nrg level make an atom not reactive or stable ◦ Metals lose their e-’s to achieve octet  They become positive ( + ) = cations ◦ Families 15 (VA), 16 (VIA), 17 (VIIA) gain e- to achieve octet  They become negative ( - ) = anions  All elements WANT 8 e-’s to become stable

 The most active metals are in the lower left corner of the periodic table  The most active nonmetals are in the upper right corner of the periodic table Fr F Most active metal Most active nonmetal Reactivity Decreases Reactivity Decreases

Periodic Trends

 Increases as you go down a group ◦ More e- = bigger radius ◦ Atoms are gaining nrg levels  Decreases as you go across a period ◦ e- are being added to the same nrg level ◦ Nuclear charge – force of attraction between e- and nucleus ◦ As you move across a period, more e- are being attracted to the nucleus

 INCREASES as you go DOWN a group because of nrg levels  DECREASES as you go ACROSS a group because of nuclear charge  Noble gases radii are found to be larger because they don’t interact with other atoms of the same element as most others do.

 Atoms can lose or gain e- to complete or empty an outer nrg level ◦ Every atom wants an octet  Ion – an atom that has a + or – charge  Metals ◦ Lose e- giving them a + charge ◦ Decreases their radius ◦ These are cations  Nonmetals ◦ Gain e- giving them a – charge ◦ Increases their radius ◦ These are anions

 Cations ◦ H +, Li +, Na +, Mg 2+, Ca 2+  Anions ◦ F -, Cl -, O 2-, S 2-, N 3-, P 3-  **noble gases don’t have ions, they are stable and DO NOT IONIZE  *carbon doesn’t ionize a lot, it “shares” ◦ When it does ionize, it gains 4 e-  Sizably increases its radius

 Nrg needed to remove an e- from an atom ◦ Unit = (kJ/mol)  ACROSS a period, it INCREASES ◦ Due to increase in nuclear charge  DOWN a group, it DECREASES ◦ Due to increased atomic radius and shielding effect  Metals = low I.E.  Nonmetals = high I.E. (especially noble gases)

 Nrg needed to remove a second e- from an atom ◦ Typically harder to remove a 2 nd e-  **The higher the I.E., the more stable the atom. Be B 1s 2s 2p More stable, full/empty sublevels Less stable, partial sublevels

 The power of an atom in a molecule to ATTRACT e- to itself ◦ Ability to “hold on to e- more” ◦ DECREASES from top to bottom of group ◦ INCREASES from left to right in periods ◦ F has the highest E.N.  High E.N.’s gain e- and form (-) ions ◦ The more stable an atom, the less likely it will attract an e-  Would result in (-)E.N.  High E.N. = High electron affinity

 Like tug-o-war ◦ Big guy (high E.N.) ◦ Little guy (low E.N.) F Decrease in E.N.

 Most active metals (lower left) have the LOWEST E.N.  Fluorine has the highest E.N.  Noble Gases have NO E.N., because they don’t typically bond  No units for E.N. because it is a comparison  Deals with compounds and bonding