The energy difference between 2s and 2p increases quite sharplyE2p-E2s:0.07E,=180kJmol-"forLi0.77E,=2000kJmol-lforFC0NFHBNeNaHeLiBe1123s2p31324562s1sE
The energy difference between 2s and 2p increases quite sharply: 1 2 2 1 : 0.07 180 kJ mol 0.77 for Li 2000 kJ mol for F p s h h E E E E
IonizationenergiesTheionizationenergyistheenergyneededtoremoveoneelectronfromtheatom,toformthepositive ion. Because of the general downward tend in orbital energies, the ionization energyincreasesacrossaperiod,butthetrendisinterruptedwheretheelectronsbegintofillanewshell, for instancebetween Be and B and between Ne and Na.The steps between N and Oand between P and S are less easily explained, and we shall return to that later.201510H He Li Be BNOFNeNaMaAISiFCLAAtomicionizationenergies(eV)
Ionization energies The ionization energy is the energy needed to remove one electron from the atom, to form the positive ion. Because of the general downward tend in orbital energies, the ionization energy increases across a period, but the trend is interrupted where the electrons begin to fill a new shell, for instance between Be and B and between Ne and Na. The steps between N and O and between P and S are less easily explained, and we shall return to that later
ZeemanEffectThe splitting of a spectral line into two or more components of slightly different frequencywhenthelightsourceisplacedinamagneticfield.Itwasfirstobservedin1896bytheDutch physicist Pieter Zeeman as a broadening of the yellow D-lines of sodium in a flameheld between strong magnetic poles.The (normal)Zeemaneffect canbe understood classically,asLorentzpredicted,as theinteraction energy of an orbiting electron with the magnetic field.This "anomalous" Zeeman effect was eventually explained by the quantum mechanicaleffects ofspin
Zeeman Effect The splitting of a spectral line into two or more components of slightly different frequency when the light source is placed in a magnetic field. It was first observed in 1896 by the Dutch physicist Pieter Zeeman as a broadening of the yellow D-lines of sodium in a flame held between strong magnetic poles. The (normal) Zeeman effect can be understood classically, as Lorentz predicted, as the interaction energy of an orbiting electron with the magnetic field. This "anomalous" Zeeman effect was eventually explained by the quantum mechanical effects of spin
SpinOneofthemoremysteriousfeaturesofquantummechanicsisthepropertycalledspin,whichhas noclassical analogue.It doeshavetheproperties of anangularmomentum, asthename implies, but it should not bethought of in classical terms.We have seen that an electron in an atom has orbital angular momentum, usually designatedby the symbol i, with quantum numbers I describing the magnitude h/i(l + 1) of theangular momentum vector, and m, describing its z component. Both of these quantumnumbershavetobeintegersbecauseoftheboundaryconditionsonthewavefunctionAn electronalsohas anintrinsicangularmomentumcalled spin,designated bythe symbolsIt has quantum numbers s and ms, describing its magnitude and z component
Spin One of the more mysterious features of quantum mechanics is the property called spin, which has no classical analogue. It does have the properties of an angular momentum, as the name implies, but it should not be thought of in classical terms. We have seen that an electron in an atom has orbital angular momentum, usually designated by the symbol መ𝒍, with quantum numbers 𝑙 describing the magnitude ℏ 𝑙 𝑙 + 1 of the angular momentum vector, and ml describing its z component. Both of these quantum numbers have to be integers because of the boundary conditions on the wavefunction. An electron also has an intrinsic angular momentum called spin, designated by the symbol 𝒔 ො. It has quantum numbers s and ms , describing its magnitude and z component
AparticlepossessesanintrinsicangularmomentumSandanassociatedmagneticmoment Ms. This spin angular momentum is represented by a hermitian operator Swhich obeys the relation S × S =its.Each type of particle has a fixed spinquantum number or spin s from the set of values s = O, , 1, , 2, ...The spin s forthe electron, the proton, or the neutron has a value . The spin magnetic moment forthe electron is given by M, =-eS/me.Spin is not described by angular coordinates in the same way as orbital angular momentum,and the quantum numbers are not restricted by boundary conditions. It turns out that theymay have half-odd-integer values in addition to the integer values.S=is+js,+ksS2=S2+S,2+S.2S2S2S=inS
Spin is not described by angular coordinates in the same way as orbital angular momentum, and the quantum numbers are not restricted by boundary conditions. It turns out that they may have half-odd-integer values in addition to the integer values. , z x y S S i S 2 2 2 2 x y z S S S S 2 2 2 S S S S S S , , , 0 x y z