The Periodic Table And Periodic Trends - Weebly

The Periodic Table and Periodic TrendsThe properties of the elements exhibit trends andthese trends can be predicted with the help of theperiodic table. They can also be explained andunderstood by analyzing the electronconfigurations of the elements. This is because,elements tend to gain or lose valence electrons toachieve the stable octet formation.

Across the Periodic Table1IA1Periods: Are arranged horizontally across the periodictable (rows 1-7)These elements have the same number of valence shells.2IIA13IIIA2nd Period233IIIB4IVB5VB6VIB456th A18VIIIA

Down the Periodic TableFamily or Group: arranged vertically down the periodic table(columns or groups 1- 18)The elements in each group have the same number of electrons inthe outermost energy level, the valence shell.1IA118VIIIAAlkali Family:1 e- in the valence IB89VIIIB1011IB12IIB4567Halogen Family:7 e- in the valence shell17VIIA

6.1The Periodic LawHow is the modern periodic table organized? In the modern periodic table, elements are arrangedin order of increasing atomic number (since therewere problems with Mendeleev’s method).

6.1The Periodic LawThe periodic law: When elements arearranged in order of increasing atomicnumber, there is a periodic repetition oftheir physical and chemical properties.– The properties of the elements within a periodchange as you move across a period from leftto right.– The pattern of properties within a periodrepeats as you move from one period to thenext.

6.1Metals, Nonmetals, andMetalloids»Metals, Metalloids, and Nonmetals in the Periodic Table

6.1Metals, Nonmetals, and MetalloidsMetals good conductors of heat and electric current. 80% of elements are metals. Metals have a high lustre, are ductile and malleable. Most are grey/silver

Metals- silver, lustrous,malleable, ductile,and good conductorsof heat andelectricity.

Metals Tend to lose electrons to formcompounds. Compounds formed between metalsand nonmetals tend to be ionic. Metal oxides (metals reacted withoxygen) tend to be basic.

6.1Metals, Nonmetals, and Metalloids–Nonmetals In general, nonmetals are poor conductors of heat and electriccurrent. Most nonmetals are gases at room temperature. Various colours and brittle A few nonmetals are solids, such as sulfur and phosphorus. One nonmetal, bromine, is a dark-red liquid.

Nonmetals Dull, brittle substancesthat are poor conductorsof heat and electricity. Tend to gain electronsin reactions withmetals to acquire noblegas configuration.

Nonmetals Substances containingonly nonmetals aremolecular compounds. Most nonmetaloxides (non-metalreacted with oxygen)are acidic.

6.1–MetalloidsMetals, Nonmetals, and Metalloids A metalloid generally has properties that are in-between metalsand nonmetals. Solids, shiny or dull, semi-conductors, brittle and not ductile The behavior of a metalloid can be controlled by changingconditions.

Metalloids Have somecharacteristics ofmetals, some ofnonmetals. For instance, siliconlooks shiny, but isbrittle and fairly poorconductor.

6.1Metals, Nonmetals, and Metalloids Examples and Uses» Uses of Iron, Copper, and Aluminum

6.1Metals, Nonmetals, and Metalloids Examples and Uses If a small amount of boron is mixed with silicon, themixture is a good conductor of electric current.Silicon can be cut into wafers, and used to makecomputer chips.

6.2Squares in the Periodic Table The periodic table displays the symbols and namesof the elements, along with information about thestructure of their atoms.

Groups or Families Elements in the same column(group) have similar properties

Alkali Metals (Group 1) Soft and reactive solids. Highly reactive withwater and air(oxygen) Silver-coloured withmetallic properties Name comes from Arabicword for ashes. Have one valenceelectron Form 1 ions

Alkali Metals Alkali metals (except Li) react with oxygen toform peroxides. K, Rb, and Cs also form superoxides:K O2 KO2 Produce bright colors when placed in flame.

Alkaline Earth Metals (Group 2) Have higher densities and melting points than alkalimetals. Light, solid and reactive metals. Have 2 valence electrons and form 2 ions Have low ionization energies, but not as low as alkalimetals.

Alkaline Earth Metals Be does not react withwater, Mg reacts onlywith steam, but othersreact readily withwater. Reactivity tends toincrease as go downgroup.

Group 17: Halogens Solid, liquid or gas Non-metallic, not lustrous, nonconductors andvery reactive Have 7 valence electrons and form -1 ions Name comes from the Greek halos and gennao:“salt formers”

Group 17: Halogens Large, negative electronaffinities– Therefore, tend to oxidize otherelements easily React directly with metals toform metal halides Chlorine added to watersupplies to serve asdisinfectant

Group 18: Noble Gases Gases, low melting and boiling points, nonreactiveHave 8 valence electrons and rarely form ionsAstronomical ionization energiesPositive electron affinities– Therefore, relatively unreactive Monatomic gases

Group 18: Noble Gases Xe forms threecompounds:– XeF2– XeF4 (at right)– XeF6 Kr forms only one stablecompound:– KrF2 The unstable HArF wassynthesized in 2000.

6.2

6.2 Representative Elements – Examples and Uses

6.2Representative Elements

6.3Periodic Trends You will learnhow properties(such as atomicsize) are related tothe location ofelements in theperiodic table.

Orbitals in Multielectron Atoms Electrons are attracted to the nucleus but also repelledby each other. Repulsion from other electrons reduces the attractionto the nucleus and this is called the shielding orscreening effect. It increases as you go down a group. The attraction the electrons have for the nucleus is thenuclear charge. It increases as you go from left toright across a row. Effective nuclear charge: the net nuclear charge feltby an electron after shielding from other electrons inthe atom is taken into account.

ALL Periodic Table Trends Influenced by three factors:1. Energy Level - higher energy levelsare further away from the nucleus. Lesspull on outer electrons.2. Charge on nucleus (# protons)– More charge pulls electrons in closer.( and – attract each other)3. Shielding effect – more levels ofelectrons repel and reduce pull on outerelectrons.

What do they influence? Energy levels and Shielding havean effect on the GROUP () Nuclear charge has an effect on aPERIOD ()

1. ATOMIC RADIUS/SIZE the radius of an atom (size)

6.3Trends in Atomic Size The atomic radius is one half of the distance betweenthe nuclei of two atoms of the same element when theatoms are joined. In general, atomic size increases from top tobottom within a group and decreases from leftto right across a period.

Trends in Atomic Size Largest atomic speciesare those found in thebottom left corner

Atomic Radius Atomic radii actuallydecrease across a row inthe periodic table, due toan increase in thenuclear charge. Within each group(vertical column), theatomic radius tends toincrease with the periodnumber. Not only isthere an additionalenergy level but theshielding effectincreases.Atomic Radii for Main GroupElementsChapter 8-37

Atomic Size - Group trends As we increase theatomic number whilegoing down a group each atom has anotherenergy level PLUSmore shielding so the atoms getbigger.HLiNaKRb

Atomic Size - Period Trends Going from left to right across a period, the sizegets smaller. Electrons are in the same energy level. But, there is more nuclear charge (more protons). Outermost electrons are pulled closer.NaMgAlSiPS Cl Ar

6.3Trends in Atomic Size

6.3Trends in Atomic Size

6.32. Trends in Ionization EnergyThe energy required to remove an electron fromthe ground state of a gaseous atom or ion iscalled ionization energy.– The energy required to remove the firstelectron from an atom is called the firstionization energy.– The energy required to remove an electronfrom an ion with a 1 charge is called thesecond ionization energy.– i.e. Second ionization energy is that energyrequired to remove the second electron, etc.

Ionization Energy It requires more energy to remove each successiveelectron. When all valence electrons have been removed, theionization energy takes a quantum leap.

Symbol irdWhy did these valuesincrease so much?1181014840356946194577530160456276

6.3Trends in Ionization EnergyGroup and Periodic Trends in Ionization Energy First ionization energy tends to decreasefrom top to bottom within a group andincrease from left to right across a period.

Trends in First Ionization Energies As one goes down acolumn, less energy isrequired to remove the firstelectron.– For atoms in the samegroup, the effectivenuclear charge isessentially the same, butthe valence electrons arefarther from the nucleus;therefore more shielding.

Trends in First Ionization Energies Generally, as one goesacross a row, it getsharder to remove anelectron.– As you go from left toright, the nuclearcharge increases, thusholding the electronsmore tightly

Trend in Ionization EnergyIonization energy:Largest toward top right corner ofPeriodic Table since these atoms holdonto their valence e- the tightest.

6.3Trends in Ionization Energy

6.3Trends in Ionization Energy

6.33. Trends in Ionic Size During reactions between metals andnonmetals, metal atoms tend to loseelectrons, and nonmetal atoms tend to gainelectrons. The transfer has a predictableeffect on the size of the ions that form. Cations are always smaller than the atomsfrom which they form. Anions are alwayslarger than the atoms from which they form.

6.3Positive and negative ions form whenelectrons are transferred between atoms.Forming a cation

6.3Forming an Anion

6.3Trends in Ionic Size Relative Sizes of Some Atoms and Ions

Ion Group trends Each step down agroup is adding anenergy level Ions therefore getbigger as you godown, because of theadditional energylevel.Li1 Na1 K1 Rb1 Cs1

Ion Period Trends Across the period from left to right, thenuclear charge increases - so they getsmaller. Notice the energy level changesbetween anions and cations.Li1 B3 Be2 C4 N3-O2-F1-

Sizes of Ions Ionic sizedepends upon:– Nuclear charge.– Number ofelectrons.– Orbitals inwhich electronsreside.

Sizes of Ions Cations aresmaller thantheir parentatoms.– The outermostelectron isremoved andrepulsions arereduced.

Sizes of Ions Anions arelarger thantheir parentatoms.– Electrons areadded andrepulsions areincreased.

Sizes of Ions Ions increase insize as you godown a column.

Sizes of Ions Isoelectronic means that ions have the samenumber of electrons. See the following examples. Ionic size decreases with an increasing nuclearcharge.

Size of Isoelectronic ions? Positive ions that have more protons wouldbe smaller (more protons would pull thesame # of electrons in closer)Al3 1312Na1 11Mg2 NeF1-1092O8N37

6.3Size generally increasesTrends in Ionic Size Trends in Ionic Size

6.34. Trends in ElectronegativityElectronegativity is the ability of an atom of anelement to attract electrons when the atom is ina compound (i.e bonded). They share the electron, but how equally do theyshare it? An element with a big electronegativity means itpulls the electron towards itself strongly! In general, electronegativity values decrease fromtop to bottom within a group. The values tend toincrease from left to right across a period.

Electronegativity Group Trend The further down a group, thefarther the electron is awayfrom the nucleus, plus the moreelectrons an atom has. Thus, more willing to share. Low electronegativity.

Electronegativity Period Trend Metals are at the left of the table.They let their electrons go easilyThus, low electronegativityAt the right side are the nonmetals. They want more electrons. Try to take them away from others High electronegativity.

6.3Trends in Electronegativity

5. Trend in Electron AffinityElectron Affinity:The energyreleased when anelectron is addedto a gaseous atom.Most favorabletoward top rightcorner of PeriodicTable since theseatoms have a greataffinity for e-.Cl e Cl