Democritus Aristotle -400 B.C. - Coined the term “atom” B.C. - Believed matter is continuous

 All matter is composed of tiny particles called atoms.  Atoms of the same element have the same properties. (mass, size, etc.)  In a chemical reaction, matter cannot be created or destroyed – Law of Conservation of Mass  Compounds always contain elements in the same ratio by mass – Law of Definite Proportions Dalton 1810

 Showed electrons are negatively charged  Every atom’s electrons have same charge

 Conclusion: most of an atom is empty space

 Thomson’s Model (1897)  Bohr’s Model (1913)  Electron-cloud Model (present)  Rutherford’s Model (1909)  Dalton’s Model (1803)

 Nucleus ◦ Contains protons and neutrons ◦ Makes up most of an atom’s mass ◦ Is positively charged  Proton (+ charge)  Neutron (0 charge)  Electron Cloud ◦ Contains electrons ◦ Makes up most of an atom’s volume

Subatomic Particles ChargeLocationMassOther Feature Proton + Nucleus1 amuDefines the element -Atomic # Neutron 0 Nucleus1 amuChange # to form isotopes Electron - Electron Cloud ~0Atom’s volume -dictate’s reactivity

 Atoms of the same element that differ in mass ◦ Atomic # = # protons ◦ # protons = # electrons ◦ Mass # = # protons + # neutrons

Silver Lead Bromine - 80

 Arranged by increasing atomic #  Rows = Periods  Columns = Groups OR Families

 The weighted average of its naturally occurring isotopes. Chemical Name Atomic # Chemical Symbol Atomic Mass (Average Atomic Mass)

 Multiply the mass of each isotope by its abundance to get the weighted average.

 Energy levels are a particular distance from the nucleus n = # e- =

 The maximum number of electrons in each nrg level is 2n 2 ◦ At n = 1, there can be 2(1) 2 = 2 e- ◦ At n = 2, there can be 2(2) 2 = 8 e- ◦ At n = 3, there can be 2(3) 2 = 18 e-

 Tells the shape  Each nrg level has a # of sublevels = to n Energy Level (n) # SublevelsSublevels 111s 222s, 2p 333s, 3p, 3d 444s, 4p, 4d, 4f

 The 3 rd quantum number (m) tells which orbital and electron occupies.  One pair (2e-) of electrons can occupy each orbital ◦ s sublevels have 1 orbital (2e-) ◦ p sublevels have 3 orbitals (6e-) ◦ d sublevels have 5 orbitals (10e-) ◦ f sublevels have 7 orbitals (14e-)  ** each orbital can hold UP TO 2 e-**

 Indicates direction of spin of e- ◦ -1/2, +1/2 (clockwise, counterclockwise)  Pauli Exclusion Principle states that no two electrons in an atom can have the same set of 4 quantum numbers. ◦ The two e- in an orbital must have opposite spins.

 Helium has 2 electrons ◦ n = 1 ◦ l = s ◦ m = 1 ◦ s = 1 up, 1 down  Helium’s electron configuration would be: Principle Quantum # # of e- Sublevel

1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f - Sublevels fill in order of increasing nrg - 1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

 e- first occupy the lowest possible nrg level available.  Electron Dot Notation – show only valence e-, those in the outer most nrg level ◦ ONLY UP TO 8e- ◦ 8 e- = stable  Valence electrons – e- in the highest nrg levels ◦ These e- are what form bonds

 Examples:

 What would the electron dot notation be for titanium?  Ti = 22e- BUT only 2 valence e-  Electron Configuration Notation  Electron Dot Notation Valence e- -d’s are NEVER valence e-, they ALWAYS fill after a high nrg level -Same for f’s

 Show all orbitals with electrons  Electrons represented as up and down arrows  Arrows must be opposite within orbitals Nitrogen (7) Fluorine (9) 1s2s 2p

 Lose or gain e- ◦ Anions – are negatively charged, having gained e- ◦ Cations – are positively charged, having lost e- ** atoms will gain or lose e- to become more stable**

 Filled and half-filled sublevels are more stable than partially filled sublevels.  This Cr takes an e- from 4s to put one e- in each of its 3d orbitals and Cu takes a 4s to fill each of its 3d orbitals  Orbitals are stable when either full or half-full 1s 2s 2p 3s 3p 4s 3d

 e- at higher nrg states are not stable  These e- want to return to their ground state to become stable ◦ Lowest possible nrg level  Distance between nrg levels is NOT all the same.

R O Y G B I V  Blue light has a higher frequency than red.

 Light of a particular wavelength (λ) has a particular frequency (ν) and nrg (E).  If ν, λ or E are known, the other 2 can be calculated. speed of light Planck’s constant

 What do the following symbols stand for? What are their units?  ν  λ  h  c  E Frequency Wavelength Planck’s Constant Speed of Light Energy

 Why each element produces a unique line spectra.

 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

 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

 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)

 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