Electronic Configuration And The Periodic Table Flashcards
What is Quantum Theory?
Matter can only emit do absorb energy in small fixed amounts
What is an atomic spectra caused by?
Electrons moving between diff energy levels - fixed for any 1 atom. We say that the energy of electrons in atoms is quantised
What happens when an electron in an atom absorbs a photon of energy?
It moves from a lower energy level to a higher one. When the electron drops back down, energy is emitted.
When are atoms said to be ‘excited’ ?
When they absorb energy and emission spectra arise from the movement of electrons from a higher to lower energy when the excited atom returns to its ‘ground state’
What does the frequency of the line in the emission spectrum represent?
The difference in energy between the levels. We call these energy levels shells/sub shells.
What does each line in an emission spectrum represent?
Radiation of a specific wavelength/frequency from which these differences in energy can be calculated
What is the ground state?
The lowest possible electronic configuration the electrons in an atom can adopt
What represents the ionisation energy of an electron?
An electron escaping from level n=1 to infinity which corresponds to the electron breaking away from the atom completely
What happens to the energy levels as energy increases?
They come closer together until they converge.
What does the difference in energy between the ground state and convergence limit correspond to?
The energy required for the electron to break away from the atom
How do you find the energy of a photon?
The difference between the 2 energy levels ( deltaE= h(nu))
What is the principal Quantum number?
n.
Determines the main energy level.
It can have values n=1,2,3etc (n=1 is nearest the nucleus)
The numbers deter me the size and energy of the shell. As n increases the potential energy and distance from nucleus increases
What is the second Quantum number?
l .
Determines the shape of the sub shell and is labelled as s,p,f,d. This can have values from 0 to (n-1)
What is Heisenberg’s uncertainty principle?
It is impossible to state precisely the position and the momentum of an electron at the same instant. So it isn’t possible to define a point in space where the electron is certain to be found and it is therefore necessary to define regions in space where the probability of finding an electron is high.
What are atomic orbitals?
The volume in space where the probability of finding an electron is greater than 90%. The overall size of each orbital is governed by n, actual shape governed by l
What is the third Quantum number?
m.
Relates to the orientation in space of the orbital. Dependant on l as m can take any whole value between -l and +l
How many electrons can each atomic orbital hold?
2
Describe s orbitals
Spherical with size and energy increasing as n increases.
Describe p orbitals.
Have a value of l=1 and therefore there are 3 possible orientations in space, corresponding to m=-1,0,+1. The 3 p orbitals are degenerate (have the same energy as each other) and the same shape, dumbbell shaped at right angles to one another. Each orbital defined as if it lies along a set of x,y,z axes. The 2p orbitals are thus 2px,2py,2pz. The 3p orbitals would be the same but larger and at higher energy.
Describe d orbitals.
Occur in five different orientations corresponding to the third quantum number m=+2,+1,0,-1,-2. Important in the examination of properties of transition metals.
What is the fourth quantum number?
The spin. Has values of +0.5/-0.5. In any orbital containing two electrons they must be paired, with spins opposed.
What is the Aufbau principle?
When electrons are placed into orbitals the energy levels are filled up in order of increasing energy, e.g. 1s before 2s.
What is the Pauli exclusion principle?
An orbital cannot contain more than 2 electrons and they must have opposite spins. E.g. [⬆️⬆️] isn’t allowed! must be [⬆️⬇️]
What is Hund’s rule?
When there are degenerate orbitals in a subshell electrons fill each one singly with spins parallel before pairing occurs. E.g. [⬆️ ][⬆️ ][⬆️ ]
What are the relative energy corresponding to each orbital in increasing order?
1s,2s,2p,3s,3p,4s,3d,4p,5s etc.
What are 5 factors which affect ionisation energy?
1) atomic size- greater atomic radius=further outermost electron is from nucleus and ionisation energy decreases.
2) nuclear charge- more protons=more difficult to remove an electron
3) shielding effect
4) subshells. E.g. Boron IE is lower than beryllium because boron involves taking one electron from 2p, but beryllium involves taking 1 electron from the full 2s subshell. Since full subshells are relatively stable, IE is greater.
5) half full subshells require more energy as they’re relatively stable.
What is electronic configuration?
The arrangement of electrons in energy levels and orbitals of an atom
What causes the spectral lines in an emission spectrum?
When an excited electron falls from a higher energy level to its ground state, releasing a photon of energy. The difference in energy relates to a specific frequency/wavelength which produces lines of that frequency/wavelength to appear as an emission spectrum
