Chapter 5 - Atomic Theory
Emission Spectrum of Atoms
Electromagnetic radiation - light energy
Wavelength(l) - distance between two adjacent peaks in the wave
White Light - separates into a continuos range of colors of the rainbow.
VISIBLE SPECTRUM
Violet - shortest, Red - longest
Energy is inversely proportional to the wavelength
Larger the wavelength the lower the energy
ATOMIC EMISSION SPECTRUM - discrete line for different wavelengths given off by a particular atom.
Bohr Hydrogen Model
- Electrons ORBIT the Nucleus
- ORBITS are QUANTIZED [a definite (discrete) distance from the nucleus].
- ENERGY is also QUANTIZED
ENERGY LEVELS - the discrete orbits available to an electron in a hydrogen atom
GROUND STATE - the lowest energy level (closest to the nucleus)
EXCITED STATE - Energy levels higher than the ground state
WAVE MECHANICS
- complex mathematical approach giving electrons mass and wave nature (light).
- Certain PROBABILITY that electron exists in a given region of space
- electrons in all atoms occupy energy levels like those of hydrogen
- level closest to nucleus has lowest energy
PRINCIPAL QUANTUM NUMBER(n)
- reference of how close to the nucleus (1 closest)
The first n=1, then n=2, etc. Capacity (how many electrons) of each level = 2n2
Principal Quantum number (n) |
Shell Capacity (2n2) |
1 |
2 |
2 |
8 |
3 |
18 |
4 |
32 |
Each level is known as a SHELL
SUBSHELLS - each shell has one or more subshell
in order of increasing energy s < p < d < f
n =1 has one subshell s
n =2 has two subshell s and p
n = 3 has three s, p, and d
n = 4 has four s, p, d, and f
Each subshell can hold a different # of electrons
s 2
p 6
d 10
f 14
ORBITALS - the region of space where there is the highest probability of finding
an electron - each orbital can hold TWO electrons.
subshell |
# electrons |
# orbitals |
s |
2 |
1 |
p |
6 |
3 |
d |
10 |
5 |
f |
14 |
7 |
ELECTRON CONFIGURATION - the designation of the electrons in an atom in specific shells and subshells of lowest energy.
AUFBAU PRINCIPLE - electrons will always fill lowest energy first.
ORBITAL DIAGRAMS - represents orbitals as boxes and electrons as arrows
Pauli Exclusion principle - No two electrons in the same orbital can have the same spin.
Spin up: and Spin down: ¯
Hund's rule - electrons occupy separate orbitals in the same subshell with parallel spins before doubling up P subshell has 3 orbitals Fill:
Electron Configuration and the periodic table
PERIODIC TRENDS
Radius of an atom - distance from the nucleus to the outermost electrons
Ionization energy(IE) - energy required to remove an electron from the gaseous atom to form a gaseous ion (ability to form positive ions).
Electron affinity(EA) - energy released when a gaseous atom adds an electron to form a gaseous ion (ability to form negative ions).