Studied by 11 people
Wavelength
The distance between two corresponding parts of a wave
emission spectrum
a spectrum of the electromagnetic radiation emitted by a source, only certain frequencies og light produced by excited atoms and ions
when do electrons emit UV radiation?
when they return to the ground state
what determines the energy of an orbital
attraction between electrons and the nucleus and inter-electron repulsions
flame test
Testing chemicals by burning a compound to look at its flame color. Certain compounds and elements burn with distinctive colors.
why are different colour observed in flame test with different elements?
electrons move to higher energy levels when heat (energy) is added, when they fall back to lower energy levels the released energy is partially part of the visible spectrum of light (colours)
electromagnetic radiation
The energy transferred through space by electromagnetic waves. (electromagneytic spectrum)
How are all electromagnetic waves the same? How do they differ?
same speed (c, speed of light) but different wavelenght
frequency
the number of waves that pass a given point per second
how are wavelenght and frequency related?
shorter wavelenght causes a higher frequency and vice versa
why are higher frequency waves dangerous?
they can penetrate through our skin etc. (cancer)
which electromagnetic waves have the most energy?
gamma rays (highest frequency)
continous spectrum
the emission of a continuous range of frequencies of electromagnetic radiation (all colours seen)
When is an emission spectrum produced?
when electrons move from a higher energy level to a lower energy level, high voltage or temperature applied to a gas
absorption spectrum
a spectrum of electromagnetic radiation transmitted through a substance, showing dark lines or bands due to absorption of specific wavelengths.
When is an absorption spectrum produced?
when electrons move from a lower energy level to a higher energy level
do the emission and absorption spectrums match? why?
yes, as the lines represent the different energy levels
ground state
The lowest energy state of an atom
photon
a particle of light
hydrogen spectrum
-The emission spectrum of hydrogen shows discrete wavelengths
-Indicates that hydrogen has discrete energy levels, only certain energy levels are allowed
quantized energy of electrons
electrons can jump between the different energy levels (lines in the emission/absorption spectrums) but not just float around (not a continuous spectrum)
are line spectras specific to each element?
yes, as they have different electron configurations (energy levels etc.)
how can the elemental composition of stars be determined?
analysing line spectras as the gases around them absord and emit certain wavelenghts> absorption spectrum can be used the analyse the different elements in the stars
the relative distances between the different energy levels (orbits)
the distance is the largest closer to the nucleus and it decreases as we go further away from it
excited states
a higher energy state than the ground state
ionization energy
The amount of energy required to remove an electron from an atom
when do electrons emit visible light?
when they return to the second energy level
when do electrons emit infrared (IR) radiation?
when thet return to the third energy level?
Bohr Model of atom
electrons orbit the nucleus in circles
are energy levels similar to orbits?
no
which electrons have the lowest energy?
the ones closest to the nucleus
why is Bohr model not perfect?
it failed to explain spectral lines of any other atom than hydrogen (more than one electron)
Is the electron a particle or a wave
both properties
why can't electrons' trajectories be precisely predicted?
we would need to know its position, direction and speed (impossible)
Heisenberg uncertainty principle
states that it is not possible to know precisely both the velocity and the position of a particle at the same time, but we can predict the likely positions of electrons
atomic orbital
a three-dimensional region around the nucleus of an atom that describes an electron's probable location (90% chance), different shapes and sizes
Shrödinger Model of the Atom
wave equation to describe the behavior of electrons
the spin of electrons
additional movement to just moving arounf the nucleuc, either clockwise (upward arrow) or anti-clockwise (downward arrow)
Pauli Exclusion Principle
No more than two electrons can occupy a space orbital, and these two electrons must have opposite spins.
why can't electrons in the same orbital spin the same direction?
so that they don't repel each other
Orbital of the first energy level
1s (1st energy level, spherical)
Orbitals in the second energy level
two sublevels: 2s 2p
sublevels of 2p
px, py, pz, the dumbbell shape can be in three different orientations (x-, y-, z-axises)
How many electrons can each orbital hold?
2 electrons
how many electrons can s hold?
2 electrons (1 orbital)
how many electrons can p hold?
6 (3 orbitals times 2)
does the diameter od orbitals vary?
no
degenerate
same energy level
how many sublevels of orbitals does the nth energy level have?
n sublevels
Orbitals in the third energy level
3s, 3p, 3d
how many electrons can d hold?
10 (5 orbitals times 2)
Orbitals in the fourth energy level
4s, 4p, 4d, 4f
how many electrons can f hold?
14 (7 orbitals times 2)
how many electrons can nth energy level hols?
2n^2
Aufbau Principle
electrons occupy the orbitals of lowest energy first
Hund's third rule
if more than one orbital in a sub-level is available, electrons occupy different orbitals to minimize the mutual repulsion(HSL theory: if the bus has seats available electrons will not sit next to another electron)
electron configuration
the arrangement of electrons in the orbitals of an atom
Why is the 4s orbital filled before the 3d orbital?
it has a lower energy and if 3d would be filled first, there could be 9 valence electrons which is not possible (maximum is eight), the levels are sensitive to inter-electron repulsion
relative energy of orbitals
depends on atomic number
Why are 4s electrons lost before 3d electrons? (ions)
once the 3d level is occupied those electrons push 4s electrons to higher energy levels > easier to lose during ionization
valence electrons
Electrons on the outermost energy level of an atom, mainly responsible for compound formation
Exceptions to the Aufbau Principle
chromium and copper
Why are Cr and Cu exceptions to the Aufbau principle?
half-filled or full (or empty) subshells are more stable (less electrostatic repulsion) as they require slighlty less energy than the Aufbau principle method
why are there more exceptions to the Aufbau principle with heavier elements?
more electrons >> more energy levels >> energy levels get closer and closer together >> electrons can jump between energy levels easier
electron configurations of ions
the electrons from outer energy levels are lost first (positive ions)
Note
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