UNIT 2: THE PERIODIC TABLE

I. The Atomic Theory 1) GREEK THEORY ALL matter is made of 4 “elements”: Earth Air Fire Water

B) DEMOCRITUS BC Matter is made of indivisible particles (atoms)

C) JOHN DALTON (1808) Elements are made of atoms. All atoms of element are identical. Atoms of a given element are different from those of any other element. Atoms combine with other atoms to form compounds. Atoms are not created not destroyed in a chem reaction.

D) J.J. THOMSON (around 1910) Proposed that the atom might be something like plum pudding (a pudding with raisins randomly distributed throughout)

E) ERNEST RUTHERFORD (1911) Gold foil experiment… Alpha particles deflected by something in air…this puzzled him…designed exp that directed the alpha particles to metal foil….foil is surrounded by detector coated with substance that flashed when hit by particles…results were different than he thought…most particles passed thru foil, some deflected at high angles and others reflected backwards….

If plum pudding model was correct, the huge alpha particles would crash thru foil like cannonballs thru paper…the large deflection could only be charged by center of concentration of positive charge SO….he concluded that the nucleus must be positive to balance the negative charge 1919: Rutherford concluded that nucleus of atom contained protons. His co-worker Chadwick showed there were neutrons in the nucleus in (1932).

F) NIELS BOHR Electron moves around nucleus in various energy levels, in circular orbits

Niels Bohr postponed his wedding and canceled his honeymoon in order to complete his theory of the atomic model.

G) QUANTUM/WAVE MECHANICAL MODEL E- s are in orbitals 1926 Ernest Schrodinger

II. Subatomic particles ProtonPositive x kg ElectronNegative9.1 x kg NeutronNeutral x kg

III. The Nucleus a) Central core of atom, positive, contains all of atoms mass there b) Atomic # = # of protons = # of electrons, IF neutral atom c) Atomic mass= sum of protons and neutrons

c) Atomic mass MOLE=unit of measurement for telling # of atoms and molecules Huge relationship 1 mole of substance = atomic mass = 6.02 x atoms (or molecules) Huge huge huge huge huge huge huge huge huge huge

d) Isotope Atoms of same element with the same # of protons but a different # of neutrons

IV. E- cloud a) Electron = negative b) Electron cloud: space in which e-s are likely to be -whirling around nucleus, in energy levels w/in cloud c) Energy levels= orbitals

Energy levels OrbitalHow many total e-?Subshells/sub-orbitals K2s=2 L8s=2, p=6 M18s=2, p=6, d=10 N32s=2, p=6,d=10, f=14

c)Valence # of electrons in outermost shell Determine chemical properties

d) Quark Particles that make up the other subatomic particles

V. THE PERIODIC TABLE A) Dmitri Mendeleev: 1869-published the table of the elements…today it’s called the PERIODIC TABLE groups elements according to properties “periodic”: repeating at regular intervals

B) columns: vertical Groups Families Valence #

c) period-horizontal rows

d) Elemental key

Mass, # atoms, #electrons, #neutrons, #protons, valence e-# ALSO: RADIOACTIVE: greater than or equal to atomic # 82 SYNTHETIC: greater than atomic # 92, also called transuranic element

E) METALS Good conductor of heat and electricity Shiny Malleable Ductile 3 or less valence electrons WHERE?

F) NONMETALS Poor conductor of heat and electricity Dull Non-malleable Non-ductile 5 or more valence electrons WHERE?

G) METALLOIDS Characteristics of both metals and nonmetals WHERE?

H) PERIODIC PROPERTIES 1) Atomic size decreases as you move from left to right across a period. Atomic size increases as you move down a period.

2) ionization energy: energy needed to remove a valence electron **This decreases as you move down a family. **It increases as you move across a family.

3) Electron affininty “attracting ability” This increases as you move down a pd. This decreases as atomic size increases.

Note: EA =EN ??? Electron affinity: the energy change when a neutral atom attracts an electron to become a negative ion. Electronegativity: the ability of an atom in a molecule to draw bonding electrons to itself.

HUGE

VI. FORCES 1) electromagnetic force: can either attract or repel particles on which it is acting *e-s stay in cloud bc of this 2) Strong force: opposes EM force between protons. Glues protons together to form nucleus 3) Weak force: key to power of sun, resp for radioactive decay 4) gravity: weakest

VII. IONS a) ion: charged particle b) Cation: positively charged particle c) Anion: negatively charged particle d) Diatomic molecules: certain atoms can not appear alone….these are called diatomic molecules **Learning tool: BrINClHOF