unit 3: atomic theory according to bossong

Question 1

Dalton

Answer 1

First Atomic Theory:
1. All matter is made of atoms.
2. Atoms of the same element are identical.
3. Law of Multiple Proportions: fixed ratios of elements in compounds.
4. Chemical reactions when atoms rearrange.

Billard Ball Model → atomic diagram is a solid sphere.

Question 2

Thomson

Answer 2

Experimented with the cathode tube. The rays went from the negatively charged plate (cathode) to the positively charged plate (anode). In another experiment, the ray was repelled by the negative charge = the ray was negatively charged.
He changed variables (took out gases, changed gases, changed material). He always got the same charge-to-mass ratio no matter what.
He decided that this negatively charged particle must be in all atoms. He called it the atom.
Plum Pudding Model → sphere with randomly placed electrons and some positive charge (the big positive).

Question 3

Rutherford

Answer 3

Supported the Plum Pudding Model, tried to back it up.
If Plum Pudding Model was true, then when alpha particles are short, it should pass through as any spot is neutral.
However, when they ran it, most of the alpha particles ran through but when it hit the positive charge, the alpha particles repelled.
Concluded that positive charge is condensed in the center as a nucleus.
Gold Foil Experiment → sphere with nucleus in the middle and electrons all around.

Question 4

Millikan

Answer 4

Millikan Oil Drop Experiment:
Dropped negatively charged oil droplets in between negative and plates. By observing the suspension of the oil drops, Millikan was able to find out the mass and charge of the electron.

Question 5

Chadwick

Answer 5

Shot alpha particles at beryllium, didn’t detect charge coming out, but something was reflecting protons → he decided that there must be a particle with a neutral charge = neutron.

Question 6

isotopes

Answer 6

atoms of the same element with the same number of protons and electrons but different number of neutrons.

Question 7

atomic mass

Answer 7

the weighted average of all isotopes of an element. unit is amu.

Question 7

two isotope notations

Answer 7

Hyphen notation: Carbon-14 (also C-14)
Atomic notation: 146 C

Question 8

Bohr

Answer 8

Was studying the hydrogen emission spectrum and concluded that those electrons were moving in orbits of FIXED ENERGY. As an electron absorbed energy, it would have to find an orbit that accommodated that energy. When it went back to ground state, it would emit the same amount of energy it absorbed as a photon.

Question 9

Schrodinger

Answer 9

Developed an equationt that describe the probability of where you would find electrons in an atom. Changed the atomic model from fixed orbits to areas with high and low probability.

Question 10

DeBroglie

Answer 10

Built on the Einstein photoelectric idea and flipped it around. DeBroglie wavelength equation: shows that something with a mass (particle) also has a wave, so everything has the duality.

Question 11

4 quantum numbers

Answer 11

Principle quantum number (n): main energy level, distance from nucleus, how much enegry is required.
Orbital quantum number aka angular momentum number (l): shape of sublevel.
Magnetic quantum number (ml): orientation (axis and dimension) of orbitals.
Spin quantum number (ms).

Question 12

sublevels in terms of n, l, ml, ms

Answer 12

S sublevel: integer, 0, 0, (+½ or -½).
P sublevel: integer, 1, (-1, 0, 1), (+½ or -½).
D sublevel: integer, 2, (-2, -1, 0, 1, 2), (+½ or -½).
F sublevel: integer, 3, (-3, -2, -1, 0, 1, 2, 3), (+½ or -½).

Question 13

electron configuration

Answer 13

Describes how electrons are distributed in its atomic orbitals. Ground states, excited states, impossible states.

Question 14

Aufbau’s rule

Answer 14

Electrons fill lower-energy atomic orbitals before filling higher-energy ones

Question 15

Hund’s rule

Answer 15

The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins (do the upspins first). Every orbital in a sublevel is singly occupied before any orbital is doubly occupied.

Question 16

Pauli’s Exclusion principle

Answer 16

No two electrons in an atom can have the same four quantum numbers (n, l, ml, ms). Plus, two electrons in the same orbital must have opposite spins.

Question 17

Heisengberg’s Uncertainty Principle

Answer 17

It is impossible to know simultaneously both the momentum (mass x velocity) and the position of a a particle with certainty.

Question 18

spectra

Answer 18

The more electrons, the more bands because the more combinations of jumping up and down energy levels.

Question 19

equations

Answer 19

E=hv, where E = energy (J), h=Planck’s constant (Js), v=frequency (Hz).
c=wavelength*v, where c=speed of light (m/s), wavelength (nm), v=frequency (Hz).

Question 20

define amu

Answer 20

A unit for expressing the mass of atoms, particles, subatomic particles, and molecules.
One-twelfth the mass of an atom of carbon-12.