general chemistry

Law of Conservation of mass

“building blocks” cannot be created or destroyed, but are rearranged in reactions

Law of definite proportion

“building blocks” form into specific ratios for different compounds

Atomic Theory

combines the law of conservation of mass and the law of definite proportions

Law of Multiple proportion

atoms combine into ratios of simple integers 

Avogadro’s Hypothesis

at the the same temperature and pressure the same volume of gas containes the same number of particles

J.J Thompsons cathode ray experiment

measured the charge-to-mass ratio of electrons, bending electrons with electric and magnetic field

What Dalton’s Atomic Theory got wrong

• Atoms are indivisible and indestructible

• mass of atoms determines the identity of atoms

Oil Drop Experiment

Significant because it measured the charge of an electron

Gold foil experiment

Discovery of the nucleus (no more plum pudding!!)

Mass spectrometry

Discovery of Isotopes

Protons 

• Charge of +1

• In the nucleus

• determines the identity of atoms 

• the number of them determines the atomic number 

Neutrons

• neutral

• in nucleus

• “glue” that holds nucleus

Electrons

• -1 charge

• To find the charge of a chemical symbol #protons-#electrons

Blackbody

• Energy level is quantized (in specific amounts)

Ultraviolet catastrophe

• classical physics says that a blackbody emits infinite amounts of energy at high frequencies. This is physically impossible

Quantum Mechanics and blackbody

• The black body can only absorb or emit energy in specific energy packets or “quanta” 

Photoelectric effect

Discovery of the photon

• experimental observations explained that increased intensity leads to more electrons ejected but kinetic energy stays the same 

• below the threshold frequency electrons cannot be ejected 

• below the threshold frequency photons do not have have enough energy to eject electrons 

• An increased frequency of light means an increase in kinetic energy 

Two-slit experiment with electrons

Shows that electrons have wave like behavior

• Electrons + two slit= interference pattern

• Only waves can have constructive and destructive interference

effective nuclear charge

• Nuclear charge decreases when there is an increase of shielding 

• Increase in nuclear charge with an increasing atomic number, number of protons added to the nucleus 

Aufbau Principle

add electrons to the orbitals with lowest energy

Hund’s rule

add electrons to empty orbital with parallel spin rather than pairing up

Ground state

electron configuration obeys all rules

Excited state

electron configuration violates hunds rule or aufbau principle

Atomic Radii

Increases going to the left and down a group

Effective nuclear charge

increases going to the right because electrons are closer to the nucleus

Electron affinity

the energy released when an electron is added

Exceptions in electron configuration

Cr[Ar]4s^13d^5

Cu[Ar]4s^13d^10

Ionization energy

energy required to remove an electron

covalent bonds

when electrons are shared

ionic bonds

when electrons are transferred