Chemistry Experience 4 - Modern Atomic Theory

quantum mechanical model

Schrodinger 1926

similar to Bohr model, e^-s have restricted values (integers)

different bc it does not specify a path for electrons orbiting the nucleus

atomic orbital

each energy level’s region of space where there is a high probability of finding an e^-

shell model

shows energy shells (1,2,3,4…), number of electrons(shell x2), and subshells (spdf)

why does the number of electrons in each principal energy shell increase as the number of the shell increases?

because there are more subshells due to higher energy levels further form the nucleus (potential energy?)

s orbital

spherical

1

1 e^-

p orbital

different orientations in space

3

6 e^-

d orbital

4/5 have cloverleaf shapes, 1 is freaky

5

10 e^-

f orbital

complicated shapes

7

14 e^-

use the subshell energies diagram to identify the subshells that hold the 25 electrons in a manganese atom, then explain.

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵

found by following the zig-zag w/ 2 e^-s per box x how many boxes per row

Heisenberg uncertainty principle

1927

• impossible to know both speed AND position of a subatomic particle

• create a wave packet of the wavelength of the SAP to get an estimate of the position

• more waves in teh packet, more momentum uncertainty. less waves, more position uncertainty

• used to create the quantum mechanical/electron cloud model of an atom

how can the scenario of watching a person on an escalator be used as an alaogy for heisenberg’s uncertainty principle?

When looking at a picture of a person on an escalator, they look “stationary” so you can’t know their speed. If you watch them moving, you can’t know their position because it is constantly changing.

Compare Daton’s original postulates to Heisenberg/Schrodinger’s quantum mechanical model

Dalton and Heis-inger both agreed on atoms being tiny little particles of matter but Heis-inger found out how to estimate electron location around the nucleus using the uncertainty principle

orbital

region around the nucleus of an atom that has a high probability of finding an electron. each orbital has 2 electrons max.

principal quantum number

• n

• values 1, 2, 3, 4, …

• tells the energy level and main shell the electron is in

• ex: n = 3 means third shell

angular momentum qunatum number

• L

• values can be zero to n-1

• 0=s, 1=p, 2=d, 3=f

• tells shape of orbital, the subshell type

• ex: L=1 means a p subshell

magnetic quantum number

• m_L

• values: integers from -L to +L, including zero

• tells which orbital within teh subshell, which orientation

• for s(L=0) m_L = -1, 0, +1 so there are three orbitals

spin quantum number

• m_s

• values: +1/2 or -1/2

• tells spin state of the electron

• each orbital holds up to 2 epectrons, which must have opposite spin states