Presentation on theme: "Beyond protons, neutrons, and electrons"— Presentation transcript:
1 Beyond protons, neutrons, and electrons The Periodic TableBeyond protons, neutrons, and electrons
2 The Modern Periodic Table The original PT was arranged by massBy Dmitri Mendeleev and J Lothar Meyer in 1869Mendeleev predicted the existence of unknown elements (which turned out to be Ge, Sc, and Ga), and predicted their properties from the patterns he sawMendeleev corrected the assumed atomic masses for elements (In, Be, U)These are reasons why he is credited with the first periodic table and is dubbed “The Father of the Modern Periodic Table” over Meyer
4 Changes….Henry Mosley changed the table to be organized by atomic number (Z) instead; it then more closely followed trends/ patterns
5 e- configuration and the PT PT also shows trends in electron configurationGroups are based upon electron configurationAlkali metals are #s1 (# is period)Alkaline earth metals are #s2 (# is period)Halogens #p5 (# is period)Noble gases #p6 (# is period)Transition metals d block (# is period -1)Inner transition metals are f block (# is period -2)
6 Blocks and l* * * orbital shape Blocks and l* * * orbital shapeThe blocks you already know correspond to the orbital of the last (outermost) e- , or valence e-s occupied
7 Effective Nuclear Charge Given by the formulaZeff = Z – SWhere Z is the number of protons in the nucleus and S is the average number of electrons between the nucleus and the electron in questionThe effective nuclear charge experienced by the outer electrons is determined primarily by the difference between the charge on the nucleus and the charge of the core electrons.
8 Effective Nuclear Charge What is the effective nuclear charge an outer electron of Na experiences?What is the effective nuclear charge an outer electron of Mg experiences?K?
9 Why is this important?The effective nuclear charge experienced by outer electrons increases as we move from element to element across any row.Why? The number of core electrons remains constant, while the nuclear charge increases.The effective nuclear charge experienced by outer shell electrons increases only slightly as we move down a family. Because of the slight change, this trend is far less important.
10 Patterns (Periods) and the PT We see patterns for many things, includingAtomic number *(not a periodic pattern, but a pattern)Electron configurationAtomic radiiIonization energyElectron affinityElectronegativityActivityDensity
11 The Periodic LawMendeleev says "The properties of the elements are a periodic function of their atomic masses"We now say: “When atoms are arranged by increasing atomic number, the physical and chemical properties show a (repeating) pattern”
12 Periodic…Summed up: Properties of elements are periodic functions of their atomic numbers.Hence, we call the table of elements the PERIODIC table (go figure)
13 Octet Rule“Atoms gain, lose, or share electrons in order to create a full outer shell”This is typically going to be eight electronsH and He are exceptions; wanting to fill the 1s orbitalH gains an electron to become H- , with the same electron configuration as HeH may want to go to no electrons, which is considered “full” even though it is emptyH+ and He+2 would have no electrons leftThe law can be used to predict several properties
14 Atomic Radii Half the distance between adjacent nuclei Half the distance between adjacent nuclei½ (2R)= atomic radius
15 Atomic Radii The radius increases as you go down a group The radius increases as you go down a groupThis is because n increasesThe radius decreases as you go across a period(Yes, this is counterintuitive)Due to the fact that you add e- as you add p+, so the nucleus is more positively charged, and each electron has the same negative chargeResults in each electron being more attracted to the (increasingly) more positive nucleus, and being pulled in closerSort of like making a magnet more powerful- it will decrease the distance where it will pull objects towards it
16 Radii (2)* The radii for the Noble gases is INCORRECT- they should be smaller!
18 Ionic Radii Larger than the neutral atom Cations (+) Anions (-) Cations (+)Smaller than the neutral atomThe electrons have less repulsion, and pull in closer to the nucleusAnions (-)Larger than the neutral atomMore electrons = more repulsion = larger electron cloud
20 Ionization Energy (Heretofore called IE) IE is the amount of energy needed to remove an electron from an atom(specifically, an isolated atom of the element in the gas phase)Measure in kJ/ molAl(g)Al(g)+ + e I1 = 580 kJ/molAl(g)+ Al(g)+2 + e I2 = 1815 kJ/mol
21 IE, continuedThe Energy needed to remove the first electron from an element is the 1st IEThe Energy needed to remove the second electron is known as the 2nd IE
22 Successive IEThere are also 3rd, 4th, 5th , and so on IEs (which are successive IEs), until you can’t pull any more offIt takes more energy to remove successive electrons than to remove the firstDue to the fact that there are then more protons than electrons, and the stronger positive charge will then act on the remaining electrons to hold them to the atom(Remember that the charge on the nucleus increases while the charge on each electron remains the same, causing more pull by the nucleus on each individual electron)
23 Why IE?Since electrons (-) want to hang around the atom (due to the + protons in the nucleus pulling on them), it takes energy to remove electronsIn generalThe smaller that atom, the more energy it takes to remove an electronBecause the electron is closer to the nucleus than in a larger atomThe fewer electrons that atom possess, the harder it is to remove an electronBecause it will hang on to them tighter as they are closer to the + charged nucleus;also, the less repulsion between electrons
26 Stuff to keep in mind…Remember (from coming up with the abbreviated electron configurations) that:Inner core electrons are those electrons from previous Noble GasValence electrons are the electrons that are on the exterior of an atomThese are the electrons that are responsible for the behavior (properties) of the element
27 Successive IEs Are higher than the first Due to the fact that there is going to be more protons than electrons at that point, resulting in a stronger attraction on the remaining electrons than there was in the first placeBasically increasingly larger jumps as each electron is removedOne jump is usually much larger than the others, because once the inner core configuration is reached, electrons are removed from the inner core, taking a lot more energyMuch bigger difference between positive nucleus and negative electron
30 Electron Affinity (EA) The energy change associated with the addition of an electron to a gaseous atomNegative values mean that energy is released when adding an e-more negative means more E released when adding an electronWants an electron more than something with a more positive valuePositive values mean that energy needs to be added to add an e-More positive means more E needed to add the electronDoes not want an added electron; takes E to do it
31 The trend for EA is? EA becomes more positive moving down the PT EA becomes more negative from left to rightFarther from the nucleusThere are several exceptions to thisThe smaller the atom, the more e--e- repulsion when adding electrons
33 Electronegativity (Eneg) The ability of an atom to attract electrons in a bondSome atoms share electrons easily, others are electron hogsThe ability to share is rated (usually) from 0 to 4Elements with 0 Eneg share easilyElements with a high (close to 4) Eneg don’t share e- well
34 Electronegativity Trends If it normally goes +, it has a low EnegIf it normally goes -, it is has a high EnegThe smaller it is, the higher the EnegThe larger it is, the lower the EnegNoble gases, which normally take no charge, we say have no Eneg values
36 Metallic characterMetallic character is acting like a metal (conductive, shiny, malleable,etc)All elements possess from very low to very high metallic character.The scale is from Fr to F.Fr has the most metallic character and F has the least.In groups, metallic character increases with atomic number because each successive element gets closest to Fr.In periods, metallic character decreases when atomic number increases because each successive element gets closest to F.
37 ReactivityThe nature (metal, non-metal, semi-metal) makes a difference in how an element’s chemical reactivityThe trends are characterized by their nature
38 Metals reactivity trend In groups, reactivity of metals increases with atomic number because the ionization energy decreases.In periods, reactivity of metals decreases when atomic number increases because the ionization energy increases.
39 Nonmetals reactivity trend In groups, reactivity of non-metals decreases when atomic number increasesbecause the electronegativity decreasesRelate to size- it increases.In periods, reactivity of non-metals increases with atomic numberbecause the electronegativity increases.Relate to size- radii decreasesRemember, the radii would have an effect on this
40 Density: in general Density of solids is greatest Density of gases Measured in g/cm3Highest in center of table (d- block)Density of gasesMeasured in g/L at STP (1atm , 0°C)Decreases as you go down a groupDecreases as you go across the tableDensity of liquidsMeasured in g/mLDensity of Hg is greater than that of Br2