Atomic Theory of Matter Flashcards
what is dalton’s atomic theory
4
- element= made of atoms
- atoms of same element=same; atoms of different element=different
- atoms cannot be created/destroyed; element cannot change to another element
- compunds=more than 1 element combine; same relative number & kind of atoms (balancing eq)
important laws in the atomic theory of matter
3
law of conservation of mass (antoine lavoisier)
law of definitie composition (joseph louis proust)
law of multiple proportions (john dalton)
what is the law of conservation of mass
3
- by antoine lavoisier
- matter is not created nor destroyed during chem/physical reactions
- total mass of reactants=total mass of products
what is the law of definite composition
2
- by joseph louis proust
- given compound has elements in constant composition and proportion (limiting & excess reactants)
what is the law of multiple proportions
if two elements form more than 1 compound, masses of A & B are in ratio of small whole numbers (NO, NO2, N2O, N2O2,N2O5)
what is the electron
by JJ Thompson in 1897 using cathode ray tubes (initially called corpuscules)
what is the cathode ray expeiment
3
- cathode rays= beams that travel from - to + electrode
- if near electric field, ray was repelled by the negative pole and it was deflected towards the positive pole=cathode ray is negatively charged (- and - repel)
- used this & adjusted electrical field strength for beam to travel undeflected; charge-to-mass ratio of electron=-1.76 x 108 C g-1
what is radioactivity
2
- by ernest rutherford
- 3 types of radiation: alpha(+), beta(-), gamma(neutral)
what is electron’s charge
- by Robert Milikan thru Milikan’s Oil Experiment
- 1909= charge of electron is 1.602x10 -19 C thru JJ Thompson’s charge-to-mass ratio of -1.76 x10 8 C g-1
- electron mass=9.10 x 10 -28
what is the Milikan’s Oil Drop Experiment
2
- oil droplets with net negative charge thru xray irradiation pass thru electrically charged plates which can slow down/speed up the fall of particles when voltage is varied depending on distance between droplets
- calculated from oil droplets that the charge is 1.602 x 10 -19 C
what is radioactivity
3
- by henri becquerel in 1896
- uranium spontaneously emits radiation (radioactivity)
- marie & pierre curie started to identify and isolate source of radiation of uranium
who is william ramsay
- 1894, found argon in atmosphere
- found helium (1895), neon (1898), krypton (1898) and xenon (1898)
- won noble peace prize in chemistry
- died due to radioactivity
who is JJ Thompson
3
- discovered electrons (called them corpuscules)
- plum pudding model (- charge scattered around positive charge)
- started separating neon isotopes by mass leading to techniques of mass spectrometry
who is marie curie
4
- investigated radioactive substances with pierre curie, husband
- discovered radium & polonium
- 2 nobel prizes (physics & chemistry)
- unit curie=radioactivity
what is the plum pudding model
2
- by JJ thompson (early 1900s)
- atom is a + charged evenly distributed sphere/cloud w/ dispersed- charged e-
what is the nuclear model of an atom
3
- by ernest rutherford thru his gold foil experiment
- discovered nucleus & proton
- also by james chadwick who found neutrons
what is rutherford’s gold foil experiment
5
- if plum pudding, laser (+ charged, ALPHA) from gold foil should go straight bec. sphere is full of negative charges (attract)
- real result: some laser bounced from the gold foil and some went straight (bounced=repelled; straight=attract); concentrated + charge at center of atom=nucleus
- nucleus = positive charge and mass of the atom
- The rest of the atom is primarily empty space.
- tiny electrons surrounding + charged nucleus = neutral charge
what are neutrons
neutral particles in nucleus & has similar mass with protons
what is the electric charge & atomic charge of a proton
+1.602 x 10 -19 C
+1
what is the electric charge & atomic charge of a neutron
0
0
what is the electric charge & atomic charge of a electron
-1.602 x 10 -19
-1
what is the mass and atomic mass of a proton
1.6726 x 10 -24
1.0073
what is the mass and atomic mass of a neutron
1.6749 x 10 -24
1.0087
what is the mass and atomic mass of an electron
9.1094 x 10 -28
0.00054858
what is atomic no.
AXZ ∆
Z
number of protons; atomic number; characteristic of element
what is mass number
AXZ ∆
A
protons + neutrons
says isotopic nature
what is a net charge
AXZ ∆ ^ #±
± = net charge
protons-electrons
what are ions
AXZ ∆ ^ #±
charged particles when an atom loses or gains electrons
what are anions
(-) charged ion (gain electron)
what are cations
(+) charged ions (loss of electrons)
what is an isotope
3
- same element, same chem properties, different radioactive properties & weights
- atoms have identical outsides but different insides (different neutrons)
- by frederick soddy (noble prize in chemistry in 1913)
how to get ave. atomic mass
3
- % to decimal
- multiply to isotope atomic mass
- get ave.
what word did atom come from
atomos “indivisible”
by democritus & leucippus
what is bohr’s model
think of solar system
- electrons moved around nucleus in orbits of fixed sizes and energies
- quantisized electron energy (definite energy level per orbit; KLMN in to out; n=1,2,3,4, etc)
- did not work for heavier atoms
- postulated: only special orbits called discrete orbits of electrons are allowed inside atom & electrons do not radiate energy as they revolve (because normally, when an electron moves in a circular motion, it gains energy but it will collapse to the nucleus making it unstable)
what is the brownian motion
when robert brown in 1827 placed pollen into water and looked at it thru a microscope and saw the pollens just jiggling = liquid atoms and pollens jiggle jiggle & einstein found the size of an atom
