relative to electrons and electron states, what does the n quantum number specify?
2.2: The Four Quantum Numbers
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The quantum numbers are parameters that describe the distribution of electrons in the atom, and therefore its fundamental nature. They are:
1. Principal Breakthrough NUMBER (n) - Represents the main free energy level, or trounce, occupied past an electron. It is always a positive integer, that is north = i, ii, iii ...
two. SECONDARY QUANTUM NUMBER (l ) - Represents the energy sublevel, or type of orbital, occupied past the electron. The value of l depends on the value of n such that fifty = 0, 1, ... n-1. This number is sometimes too chosen azimuthal, or subsidiary.
3. MAGNETIC QUANTUM NUMBER (ml ) - Represents the number of possible orientations in iii-D infinite for each type of orbital. Since the type of orbital is determined by l, the value of ml ranges between -l and +l such that ml = -fifty, ...0, ...+50.
4. SPIN Quantum NUMBER (chiliadS ) - Represents the two possible orientations that an electron can take in the presence of a magnetic field, or in relation to another electron occupying the aforementioned orbital. But two electrons can occupy the same orbital, and they must have opposite spins. When this happens, the electrons are said to be paired. The immune values for the spin quantum number ms are +ane/ii and -1/2.
According to Heisenberg'due south uncertainty principle, it is impossible to know the electron's velocity and its position simultaneously. The exact position of the electron at whatsoever given fourth dimension cannot be known. Therefore, it is incommunicable to obtain a photographic moving-picture show of the atom like we could of a busy street. Electrons are more like fast-moving mosquitoes in a swarm that cannot exist photographed without appearing blurred. The uncertainty about their position persists fifty-fifty in the photograph. An culling picture of the swarm tin exist obtained by describing the area where the mosquitoes tend to be full-bodied and the factors that determine their preference for certain locations, and that'southward the best nosotros can do.
The quantum numbers provide us with a moving-picture show of the electronic organization in the atom relative to the nucleus. This arrangement is non given in terms of exact positions, like the photograph of a street, but rather in terms of probability distributions and potential energy levels, much like the mosquito swarm. The potential energy levels are described by the main breakthrough number n and past the secondary breakthrough number l. The probability distributions are given by the secondary breakthrough number l and past the magnetic breakthrough number ml .
The now outdated solar system model of the cantlet allows us to visualize the meaning of the potential free energy levels. The main energy levels, too called shells, are given by the main quantum number due north.
THE RELATIONSHIP BETWEEN POTENTIAL Energy AND STABILITY IS INVERSE
As the potential energy of a system increases, the organisation'southward stability is more easily disrupted. Equally an example consider the objects on the earth. Objects that are positioned at ground level have lower potential energy than objects placed at high altitudes. The object that's placed at high distance, exist information technology a aeroplane or a rock at the tiptop of a mountain, has a higher "potential" to fall (lower stability) than the object that'due south placed at footing level. Systems tend towards lower levels of potential energy, thus the tendency of the aeroplane or the stone to fall. Conversely, an object placed in a hole on the footing does not have a trend to "climb out" considering its potential energy is even lower than the object placed at ground level. Systems do not naturally tend towards states of college potential energy. Another mode of saying the same thing is to say that systems tend towards states of college stability.
In the instance of the electrons in the cantlet, those at lower levels of potential energy (lower shells, or lower northward) are more than stable and less easily disrupted than those at college levels of potential free energy. Chemic reactions are fundamentally electron transfers between atoms. In a chemical reaction, it is the electrons in the outermost beat out that react, that is to say, become transferred from i atom to another. That's considering they are the virtually easily disrupted, or the most available for reactions. The outermost beat is the market where all electron trade takes place. Accordingly, it has a special proper name. It is called the valence shell.
Now, the solar system model of the atom is outmoded because it does not accurately depict the electronic distribution in the atom. Electrons practice not revolve around the nucleus post-obit elliptical, planar paths. They reside in three-D regions of infinite of various shapes called orbitals.
An orbital is a region in iii-D space where there is a loftier probability of finding the electron.
An orbital is, so to speak, a house where the electron resides. Only two electrons can occupy an orbital, and they must do so with opposite spin breakthrough numbers 1000south . In other words, they must be paired.
The type and shape of orbital is given by the secondary quantum number l. Every bit we know, this number has values that depend on n such that l = 0, ane, ... northward-ane. Furthermore, orbitals are not referred to by their numerical l values, but rather by modest instance letters associated with those values. Thus, when l = 0 we talk about southward orbitals. When l = 1 we talk about p orbitals. When fifty = 2 we talk about d orbitals, so on. In organic chemistry, we are mostly concerned with the elements of the second row and therefore will seldom refer to l values greater than 1. We'll be talking mostly virtually southward and p orbitals, and occasionally most d orbitals in reference to third row elements.
Since the value of l depends on the value of n, merely certain types of orbitals are possible for each n, equally follows (simply the highest energy level is shown for each row of elements):
FIRST ROW ELEMENTS:n= onel= 0 onlysouth orbitals are possible, denoted as1s orbitals.
SECOND ROW ELEMENTS:n=2l= 0sorbitals are possible, denoted as2s orbitals.
l= iporbitals are possible, denoted every bitiip orbitals.
THIRD ROW ELEMENTS:n= 3l=0southward orbitals are possible, denoted every bit3s orbitals
l=1 p orbitals are possible, denoted asthreep orbitals,
l=ii and d orbitals are possible, denoted as3d orbitals.
The shapes associated with southward and p orbitals are shown below. For d orbitals refer to your general chemistry textbook. The cherry dot represents the nucleus.
Finally, the orientations of each orbital in 3-D space are given by the magnetic breakthrough number ml . This number depends on the value of 50 such that ml = -l, ...0, ...+l. Thus, when l = 0, ml = 0. At that place is simply one value, or merely one possible orientation in 3-D space for s-orbitals. That stands to reason, since they are spherical. In the case of p-orbitals l = 1, then mfifty = -i, 0, and +1. Therefore, in that location are three possible orientations in 3-D space for p-orbitals, namely along the x, y, and z axes of the Cartesian coordinate organization. More specifically, those orbitals are designated equally p10 , py , and pz respectively
Source: https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_I_(Cortes)/02%3A_Atomic_Structure/2.02%3A_The_Four_Quantum_Numbers
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