Presentation on theme: "Electronic Structure of Atoms & Periodic Table"— Presentation transcript:
1Electronic Structure of Atoms & Periodic Table CHEMISTRY - DMCU 1233Fakulti Kejuruteraan Mekanikal, UTeMLecturer:IMRAN SYAKIR BIN MOHAMADMOHD HAIZAL BIN MOHD HUSINNONA MERRY MERPATI MITANElectronic Structure of Atoms & Periodic TableChapter 4
24.1 HISTORY OF ATOMIC MODEL ContributorModelExplanationJohn Dalton(1805)Billiard Ball ModelDaltons atomic model was represented as a small united ball similar to a very tiny ball.J. J Thomson(1897)Plum Pudding ModelThomson discovered the electron, a negatively charged particle. The atom was described as a sphere of positive charge with electrons embedded in it.Ernest Rutherford (1911)Solar System ModelRutherford discovered the proton, a positively charged particle in an atom. The proton and most of the mass of the atom were concentrated in the central region called the nucleus. The electrons moved in the spherical space outside the nucleus.Neils Bohr (1913)Bohr ModelAccording to Bohr, the electrons in an atom were not randomly distributed around the atomic nucleus, but moved around the nucleus in fixed orbits (shell). Each orbit formed a circle and had a fixed distance from the nucleus.
34.1 HISTORY OF ATOMIC MODEL Plum Pudding ModelBilliard Ball ModelBohr ModelSolar System Model
4A quantum number describes the energies of electrons in atoms 4.2 Quantum NumbersA quantum number describes the energies of electrons in atomsThe Bohr model was 1-D model that used one quantum number to describe the distribution of electrons in the atom that representative of the size of the orbit, which was described by the principal quantum number (n).Meanwhile Schrödinger's model allowed the electron to occupy in 3-D space to describe the orbitals in which electrons can be found.Each electron in an atom is described by four different quantum numbers.The first three quantum number from Schrödinger's wave equations are the principal (n), angular (l), and magnetic (ml) quantum numbers describe the size, shape, and orientation in space of the orbitals on an atom.The fourth quantum number spin (ms) specifies how many electrons can occupy that orbital.
54.2 Quantum Numbers Principal quantum number – ( n ) Angular momentum quantum number – ( l )Magnetic quantum number – ( ml )Spin quantum number – ( ms )
6Quantum Numbers (n, l, ml, ms) Principal quantum number nn = 1, 2, 3, 4, ….Specifies the energy of an electron and the size of the orbital (the distance from the nucleus of the peak in a radial).All orbitals that have the same value of n are said to be in the same shell (level)The total number of orbitals for a given n value is n2n=3n=2n =1
7Quantum Numbers (n, l, ml, ms) Angular momentum quantum number lfor a given value of n, l = 0, 1, 2, 3, … n-1Specifies the shape of an orbital with a particular principal quantum number.The secondary quantum number divides the shells into smaller groups of orbitals called subshells (sublevels).l = s orbitall = p orbitall = d orbitall = f orbitaln = 1, l = 0n = 2, l = 0 or 1n = 3, l = 0, 1, or 2Shape of the “volume” of space that the e- occupies
11Quantum Numbers (n, l, ml, ms) Magnetic quantum number mlfor a given value of l ml = -l, …., 0, …. +lSpecifies the orientation in space of an orbital of a given energy (n) and shape (l).This number divides the subshell into individual orbitals which hold the electrons.There are 2l+1 orbitals in each subshell.for l = 0 (s orbital) ml = 0if l = 1 (p orbital), ml = -1, 0, or +1if l = 2 (d orbital), ml = -2, -1, 0, +1, or +2orientation of the orbital in space
14Quantum Numbers (n, l, ml, ms) Spin quantum number msms = +½ or -½Specifies the orientation of the spin axis of an electron.An electron can spin in only one of two directions (sometimes called up and down).ms = +½ms = -½Experimental arrangement for demo the spinning motion of electronsQ & A
15(orientation of the subshell's shape) Quantum numberSymbolMeaningRange of valuesValue examplesprincipalnshell1 ≤ nn = 1, 2, 3, …angular momentumℓsubshell(s orbital is listed as 0,p orbital as 1 )0 ≤ ℓ ≤ n − 1for n = 3: ℓ = 0, 1, 2 (s, p, d)magneticmℓOrbital(orientation of the subshell's shape)−ℓ ≤ mℓ ≤ ℓfor ℓ = 2: mℓ = −2, −1, 0, 1, 2spinmsspin of the electron(−½ = "spin down",+½ = "spin up")−s ≤ ms ≤ sfor an electrons = ½, so ms = −½, +½
16Relation between quantum number, atomic orbital and number of an electronnlmlNumber of orbitalsOrbital NameNumber of electrons11s22s-1, 0, +132p63s3p-2, -1, 0, +1, +253d1044s4p4d-3, -2, -1, 0, +1, +2, +374f14
17Quantum Numbers (n, l, ml, ms) Existence (and energy) of electron in atom is described by its unique Quantum NumbersPauli exclusion principle(Wolfgang Pauli, Nobel Prize 1945)No two electrons in the same atom can have identical values for all four of their quantum numbersTwo electrons in the same orbital must have opposite spins.Because an electron spins, it creates a magnetic field, which can be oriented in one of two directions.For two electrons in the same orbital, the spins must be opposite to each other; the spins are said to be paired
18Diamagnetic Paramagnetic all electrons paired unpaired electrons 2p 2p The substances are not attracted to magnets and are said to be diamagnetic.Atoms with more electrons that spin in one direction than another contain unpaired electrons. These substances are weakly attracted to magnets and are said to be paramagnetic.DiamagneticParamagneticall electrons pairedunpaired electrons2p2p
19Quantum Numbers (n, l, ml, ms) Shell – electrons with the same value of nSubshell – electrons with the same values of n and lOrbital – electrons with the same values of n, l, and mlHow many electrons can an orbital hold?
20How many 2p orbitals are there in an atom? How many electrons can be placed in the 3d subshell?Q & A
214.3 Electron configuration Electron configuration is how the electrons are distributed among the various atomic orbitals in an atom.number of electrons inthe orbital or subshell1s1principal quantumnumber nangular momentumquantum number lOrbital diagram is shows the spin of the electron1s1H
22Order of orbitals (filling) in multi-electron atom “Fill up” electrons in lowest energy orbitalsAufbau principle - electrons fill orbitals starting at the lowest available (possible) energy states before filling higher states.1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f
23Outermost subshell being filled with electrons The order in which the electrons are filled in can be read from the periodic table in the following fashion
25The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins (Hund’s rule).Ne 10 electronsNe 1s22s22p6F 9 electronsF 1s22s22p5O 8 electronsO 1s22s22p4N 7 electronsN 1s22s22p3
26What is the electron configuration of Mg? What are the possible quantum numbers for the last (outermost) electron in Cl?
27Electron Configurations of Cations and Anions Of Representative ElementsNa [Ne]3s1Na+ [Ne]Atoms lose electrons so that cation has a noble-gas outer electron configuration.Ca [Ar]4s2Ca2+ [Ar]Al [Ne]3s23p1Al3+ [Ne]H 1s1H- 1s2 or [He]Atoms gain electrons so that anion has a noble-gas outer electron configuration.F 1s22s22p5F- 1s22s22p6 or [Ne]O 1s22s22p4O2- 1s22s22p6 or [Ne]N 1s22s22p3N3- 1s22s22p6 or [Ne]
28Cations and Anions Of Representative Elements +1+2+3-3-2-1
29Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne Na+: [Ne]Al3+: [Ne]F-: 1s22s22p6 or [Ne]O2-: 1s22s22p6 or [Ne]N3-: 1s22s22p6 or [Ne]Na+, Al3+, F-, O2-, and N3- are all isoelectronic with NeWhat neutral atom is isoelectronic with H- ?
30Electron Configurations of Cations of Transition Metals When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n – 1)d orbitals.Fe: [Ar]4s23d6Mn: [Ar]4s23d5Fe2+: [Ar]4s03d6 or [Ar]3d6Mn2+: [Ar]4s03d5 or [Ar]3d5Fe3+: [Ar]4s03d5 or [Ar]3d5
32Q & A sessionName the orbital described by the following quantum numbers :n = 3, l = 0n = 3, l = 1n = 3, l = 2n = 5, l = 0
33Give the n and l values for the following orbital Q & A sessionGive the n and l values for the following orbital a. 1s b. 3s c. 2p d. 4d e. 5fWhat and the possible ml values for the following types of orbital? a. s b. p c. d d. f
34How many possible orbital are there for n = a. 4 b. 10 Q & A sessionHow many possible orbital are there for n = a. 4 b. 10How many electrons can inhabit all of the n = 4 orbital?Place the following orbital in order of increasing energy: 1s, 3s, 4s, 6s, 3d, 4f, 3p, 7s, 5d, 5p
35Write electron configurations for the following atoms: a. H b. Li+ Q & A sessionWrite electron configurations for the following atoms: a. H b. Li+ c. N d. F- e. Ca
36Q & A sessionDraw an orbital diagrams for atoms with the following electron configurations:1s22s22p63s23p3
394.4 HISTORY OF THE PERIODIC TABLE Antoine Lavoisier (1743–1794)Classify elements into four groups including light and heat, into metals and non-metals.
404.4 HISTORY OF THE PERIODIC TABLE Johann Dobereiner (1780–1849)The first significant groupings of elements by place certain elements in groups of three known as The Law of Triads.Founded that strontium had about the average properties of calcium and barium, and grouped these three together.Several more triad groups, including the halogen triad of chlorine, bromine, and iodine, and the alkali metal triad of lithium, sodium, and potassium.However, due to the inaccuracy of many measurements, including atomic weight, the relationship between large element groups could not be exacted
414.4 HISTORY OF THE PERIODIC TABLE John Newlands (1837–1898)arranged known elements horizontally in the ascending order of their atomic massesEach row consisted of seven elements.Founded that elements with similar propertiesrepeated at every eighth element.This arrangement was known as the Law of OctavesHowever, this law was only obeyed by the first 17 elements.There were no positions allocated for elements yet to be discovered
424.4 HISTORY OF THE PERIODIC TABLE Lothar Meyer (1830–1895)Plotted a graph of atomic volume against atomic mass for all known elements.Founded that elements with the same chemical properties occupied the same relative positions on the curve.Showed that the properties of the elements were in a periodic pattern with their atomic masses.Proved that the properties of the elements recur periodically.
434.4 HISTORY OF THE PERIODIC TABLE Dmitri Mendeleev (1834–1907)Showed that the properties of elements changed periodically with their atomic mass.Arranged the elements in the order of increasing atomic mass and grouped them according to similar chemical properties.Able to predict the properties of undiscovered elements and left gap for these elementsFor examples correctly predicted the properties of the elements gallium, scandium and germanium which were only discovered laterMendeleevs table was used as a blueprint for the modern periodic tableMendeleev’s periodic table
444.4 HISTORY OF THE PERIODIC TABLE Henry J. G. Moseley (1887–1915)Based on the x-ray spectrum of elements studies, he concluded that the proton numbers should be used as a basis for the periodic change of chemical properties instead of the atomic mass.Rearranged the elements in the ascending order of their proton numbersSimilar to Mendeleev, Moseley left gaps for elements yet to be discovered.produced a periodic table which was almost the same as Mendeleevs periodic table.Due to Moseley’s work, the periodic table was successfully developed and being used today.The modern periodic table is based on the arrangement of elements in the ascending order of their proton numbers.
454.4 HISTORY OF THE PERIODIC TABLE Glenn Seaborgdiscovered that the transuranium elements that have atomic numbers from 94 to 102, resulting in the redesign of the periodic tableTechnically, both the lanthanide and actinide series of elements are to be placed between the alkaline earth metal and the transition metal.However, by doing this, the periodic table would be too wide.Thus, the lanthanide and actinide series of elements were placed under the rest of the periodic table.Dr Seaborg and his colleagues were also responsible for identifying more than 100 isotopes of elements.
464.5 MODERN PERIODIC TABLEThe periodic table is a systematic classification of elements whereby elements with the same chemical properties are placed in the same group.The elements in the periodic table are arranged in rows called the periods and columns which are known as the groups
474.5 MODERN PERIODIC TABLE Groups There are 18 groups of elements in the periodic table.Some of these groups have special names:(a) Group 1 elements are called alkali metals.(b) Group 2 elements are called alkaline earth metals.(c) Group 3 to Group 12 elements are known as transition elements.(d) Group 17 elements are called halogens.(e) Group 18 elements are called noble gases.Each member of a group shows similar chemical properties although their physical properties such as density, melting point and colour show a gradual change when descending the group.
484.5 MODERN PERIODIC TABLE Periods There are seven rows from period 1 to period 7.The elements are arranged horizontally in the ascending order of their proton numbers in the periodic table.The position of the period of an element in the periodic table is determined by the number of shells occupied with electrons in the atom.Period 1 has 2 elements only H and He,Periods 2 and 3 have 8 elements each.Periods 4 and 5, they have 18 elements each and they are called the long periods.Period 6 has 32 elements whereas the elements with proton number 58 to 71 are separated and are grouped below the periodic table known as the Lanthanide Series.Period 7 has 32 elements, the elements with proton number 90 to 103 are grouped below the periodic table known as the Actinide Series.
49Periodic Classification Classification as metals and non-metals(a) Metals – a good conductor of heat and electricity.(b) Non-metals - a poor conductor of heat and electricity.(c) Metalloids – a intermediate between metal and non-metal properties
50Periodic Classification Ground State Electron Configurations of the ElementsThe similarity of the outer electron configuration (same type of valence electrons) makes the elements in the same group resemble one another in chemical behavior.ns2np6ns2np1ns2np2ns2np3ns2np4ns2np5ns1ns2d1d5d104f5f
51Periodic Classification Classification based on subshell filled with electron
52Periodic Classification Representative elements (incompletely filled s and p subshells)Transition metals (incompletely filled d subshells)Noble gases (completely filled p subshells)Actinides (incompletely filled 5f subshells)Lanthanides (incompletely filled 4f subshells)Zn, Cd, Hg (neither representative element nor transition metals)
53the periodic table of elements Periodic TrendsPeriodic trends are the tendencies of certain elemental characteristics to increase or decrease as one progresses along a row or column ofthe periodic table of elementsElemental characteristicsAtomic radiusIonization energyElectron affinityElectronegativityMetallic propertiesNon-metallic properties
54Periodic Trends Atomic radius The atomic radius is the distance between an atom's nucleus and its valence electrons in an atom.The atomic radius tends to decrease as one progresses across a period from left to right because the effective nuclear charge increases, thereby attracting the orbiting electrons and reducing the radius.The atomic radius usually increases while going down a group due to the addition of a new energy level (shell).
55Periodic Trends Ionic Radius The ionic radius is different from the atomic radius of an element.Positive ions are smaller than their uncharged atoms.Negative ions are larger than their atoms.
56Periodic Trends Ionization energy The ionization potential is the minimum amount of energy required to remove one electron from each atom.Ionization energies increase moving from left to right across a period (decreasing atomic radius).Ionization energy decreases moving down a group (increasing atomic radius).
57Periodic Trends Electron affinity The electron affinity described as the energy gained by an atom when an electron is added.Electron affinities becoming increasingly from left to rightElectron affinities change little moving down a group, however they do generally become slightly more positive (less attractive toward electrons)
58Periodic Trends Electronegativity Electronegativity refers to the ability of an atom to attract the electrons of another atom to it when those two atoms are associated through a bond.Electronegativity generally increases moving across a period and decreases moving down a group.Electronegativity plays a very large role in the processes of Chemical Bonding.
59Periodic Trends Metallic properties Metallic property decreases across a period with increase in number of valence electrons as well as a decrease in atomic radius, and it increases down the group with increase in number of shells and atomic radius.Non-metallic propertiesNon-metallic property increases across a period and decreases down the group due to the same reason