Chapter 9 - Electrons in Atoms and the Periodic Table Flashcards
Electromagnetic Radiation
a type of energy that travels through space at a constant speed of 3.0 x 10^8 m/s
Wavelength
the distance bw adjacent wave crest
- for visible light, wavelength determines color
- the shorter the wavelength, the greater the energy
Red light
longest visible wavelength
750nm
Violet light
shortest visible wavelength
400nm
Photon
particle of light
a single packet of light energy
-the shorter the wavelength, the greater the energy in photons
ex) violet has a short wavelength and carries more energy per photon
Speed of Light
3.0 x 10^8 m/s
Electromagnetic Spectrum
entire range of electromagnetic radiation from 10^5 m (low energy) to 10^-15 m (high energy)
-visible light is minute(~10^-6.5)
Gamma Ray
shortest wavelength
- produced by sun and stars
- damages visible molecules
X-Rays
pass thru substances that block visible light
- short wavelength
- damages visible molecules
UltraViolet UV light
component of sunlight that produces sunburn or suntan
-damages visible molecules
Visible light
ranges from violet to red
-photons do not damage biological molecules
Infrared Light
- the heat we feel when we place a hand near a hot object is infrared light
- night vision goggles show the infrared light
Microwaves
- used for radars and microwave ovens
- efficiently absorbed by water
Radio Waves
the longest wavelength used to transmit signals used by AM, FM radio, cell phones, tv
Wavelength vs. Frequency vs. Photon
inverse relationship.
High wavelength=Low frequency=Low energy per photon
Emission Spectrum
the result of separating light emitted by an individual element
Bohr Model
- electrons travel around the nucleus in circular orbits at specific fixed distances fr the nucleus (not bw orbits)
- the energy of each Bohr Orbit is quantized and specified by a quantum number
- energy of each orbit increases w/increasing quantum no.
Quantum Number
n: 1,2,3,…
- energy of each orbit increases w/increasing N
Excitation/Relaxation of Electrons
- when energy is put into an atom, electrons are excited into higher-energy orbits
- when an electron relaxes from higher orbits into lower-energy orbits, the atom emits light
- the energy + wavelength of the emitted light corresponds to the energy difference bw the two orbits in the transition
- since the energy is fixed + discrete, the emitted light is also fixed+ discrete
Quantum-Mechanical Model
Bohr orbits are replaced with quantum-mechanical ORBITALS
-electron’s path is unpredictable
Orbitals
represents probability maps that show a statistical distribution of where the electron is likely to be found
- not an exact path an electron takes
- represented by a number + a letter
- vs orbit which was a circular path + represented by a number
Principal Quantum Number (n)
specifies the principal shell of the orbital
-the higher the principal quantum number, the higher the energy of the orbital
n= 1,2,3,…
Subshells (s, p, d, f)
the number of subshells in a given principal shell is equal to the value of n
ex) n= shell 2 = 2 subshells
- the letter indicates the subshell of the orbital and specifies the shape
2s orbital
spherical shape
- higher in energy and larger than 1s orbital
Ground State
lowest energy state
2p subshell
contains 3 2p orbitals
-dumbbell shape but each at different orientations
3s and 3p subshell
contains 3 subshells (s, p, d)
-3s + 3p orbitals are similar to 2s + 2p orbitals but slightly larger and higher in energy
3d subshell
- contains 5 d orbitals
- looks like 4 leaf clovers of different orientations and one dumbbell surrounded by a donut
4s, 4p, 4d subshell
similar to 3s, 3p, 3d orbitals but slightly larger and higher energy
4f subshells
contains 7 orbitals
1 subshell
has a single spherical orbital
Excited State
when an electron is in a higher energy orbital, they are in an excited state
- unstable and will usually fall/relax back to lower energy orbitals
- relaxing into lower energy orbitals emit light
Electron Configuration
illustrates the occupation of the orbitals by electrons for a particular atom
Pauli Exclusion Princicple
orbitals may hold no more than 2 electrons with opposing spins
Hund’s Rule
when filling orbitals of equal energy, electrons fill them singly first w parallel spins
[Noble Gas]
when writing an electron configuration beyond a noble gas, it can be shortened by replacing a portion with the noble gas sign with brackets
ex)
[Ne] = 1s2 2s2 2p6
Na: [Ne]3s1
Electron configuration order
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s
Electron configuration order
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f
Valence Electrons
electrons in the outermost principal shell
-the group number (such as 1A-8A) tells how many valence electrons there are
Si 1s2 2s2 2p6…3s2 3p2
……“core e”………“valence e”
2+2=4 valence e. Si is in group 4A
Outermost principal shell
the principal shell with the highest principal quantum number (n)
- involved in chemical bonding
- electrons are held more loosely and are most easily lost or shared
Core Electrons
all electrons NOT in the outermost principal shell
ex)
Si 1s2 2s2 2p6…3s2 3p2
……“core e”………“valence e”
s-block elements
Groups 1A, 2A, and Helium
p-block elements
Groups 3A-8A
except He
d-block elements
Groups 3B-8B, 1B-2B
(transition metal)
principal quantum number of d shells are (n-1)
ex) Cu is in row 4, but has 3d^10
f-block elements
The separate portion of the transition metals
writing an electron configuration based on the periodic table
- core/inner e- configuration is replaced w [noble g]
- row # = highest principal #
- elements w d shells, the d# = row#-1
Ionization Energy
- the energy required to remove an e- from the atom in the gaseous state
- as you move across the periodic table from left to right, ion.energy INCREASES
- as you move down (top to bottom) the periodic table, ion.energy DECREASES
Na + (ionization energy) ->Na+ +e-
atomic size on the periodic table
- as you move across the periodic table from left to right, atomic size DECREASES
- as you move down (top to bottom) the periodic table, atomic size INCREASES
Metallic Character
- as we move across the periodic table, the metallic character decreases
- as we move down a column, metallic character increases
