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Home , Chemical symbol

Language of includes chemical symbols of elements, chemical , & chemical equations AllAll knownknown elementselements ((ca.100)ca.100) areare arrangedarranged inin PeriodicPeriodic TableTable..

EachEach elementelement hashas itsits ownown 1stcharacter namename && chemicalchemical symbolsymbol:: is CAPITAL SodiumSodium NaNa SulfurSulfur SS 2nd (if any) is low-key PotassiumPotassium KK PhosphorusPhosphorus PP HydrogenHydrogen HH CopperCopper CuCu OxygenOxygen OO GoldGold AuAu IronIron FeFe MercuryMercury HgHg TinTin SnSn LeadLead PbPb CoCo isis elementelement ,cobalt, whilewhile COCO isis carboncarbon monoxide,monoxide, aa compound.compound. CompoundsCompounds areare formedformed byby combinationscombinations ofof elements,elements, writtenwritten asas aa chemicalchemical formulaformula::

COCO22 HH22OO CHCH44 BNBN

CombiningCombining intointo compounds,compounds, atomsatoms changechange theirtheir properties:properties: CarbonCarbon CC isis aa blackblack stone,stone, ,sulfur, SS isis aa yellowyellow powder,powder, butbut carboncarbon disulfide,disulfide, CSCS2 isis aa toxictoxic liquid.liquid. RearrangementRearrangement ofof atomsatoms resultingresulting inin aa newnew chemicalchemical compoundcompound isis aa CHEMICALCHEMICAL REACTION:REACTION:

HH22 ++ ClCl22 →→ 22HClHCl

++ →→ STRUCTURESTRUCTURE OFOF ATOMATOM Humphry Davy, by 1808, found that ELECTRICAL CURRENT DECOMPOSES SOME SUBSTANCES TO ELEMENTS: (+/-)

CuClCuCl2(aq) →→ CuCu(s) ++ ClCl2(g)

Michael Faraday (1791-1867) introduced the concept of IONSIONS as ELECTRICALLY CHARGED ATOMS that move to the battery poles, according to the Coulomb law:

+ -

Anode: + - Cathode:

- - 2+ - o 2Cl -2e → Cl2 Cu +2e → Cu Anions ( - ) Cl- Cu2+ Cations (+) travel to, & travel to, & discharge at discharge at anode [+] cathode [-] + cal cal ner ner ri ri

in in rxns rxns

, , - - Cl ), ), Cl : : 2 2 , ,

in their charge. in their charge. , Cl Cl , – – . 2+ 2+ . ion les les

ppear in a chemical ppear in a chemical a a

unds due to their opposite elect unds due to their opposite elect - -

c partic c partic i i Cl Cl are involved in chemical are involved in chemical + + neutral atom neutral atom stroyed in chemistry, must have some (in free , (in free chlorine, stroyed in chemistry, must have some e chloride chloride e Na Na subatom subatom ion, Cu atoms do not dis atoms do not dis copper ion, Cu atom atom Cl Cl put forward put forward , with its , with its can exist either as can exist either as Cl Cl negative negative Berzelius Berzelius outer electrons outer electrons

neutral neutral The ELECTRIC THEORY OF CHEMICAL BOND or as a positive The ELECTRIC THEORY OF CHEMICAL BOND a a i.e. although i.e. although transformation, they somehow change transformation, they somehow change or as a positive structure structure charges: charges: atoms, though never d atoms can either be neutral, or electrically charged. atoms, though never d atoms can either be neutral, or electrically charged. Only ∴ Element Element Cu can exist as a ∴ ∴ Element Element Cu can exist as a ∴ Thus: Thus: or as a or as a Jacob J. Jacob J. atoms are held together in compo atoms are held together in compo Only ELEMENTSELEMENTS ININ PERIODICPERIODIC TABLETABLE

EachEach elementelement asas postedposted inin thethe Table,Table, has:has: aa NAMENAME,, ,potassium, ,hydrogen, …… aa SYMBOLSYMBOL,, ,K, Na,Na, Cu,Cu, ClCl,, …… anan ATOMICATOMIC NUMBERNUMBER ZZ (integer(integer only)only) && anan atomicatomic massmass AA (usually(usually nonnon--integer)integer)

55.847

26 Fe AtomicAtomic numbernumber ZZ isis thethe positivepositive chargecharge ofof thethe nucleusnucleus && thethe numbernumber ofof protonsprotons inin itit

AtomicAtomic massmass isis thethe sumsum ofof massesmasses ofof protonsprotons && .neutrons.

Why is non-integer? Because natural elements consist of a mix of : Atoms with the same , but different . ,Neon, NeNe:: Z=10Z=10 threethree isotopesisotopes pp nn AA NeNe--2020 90.51%90.51% 1010 1010 2020 NeNe--2121 0.21%0.21% 1010 1111 2121 NeNe--2222 9.22%9.22% 1010 1212 2222 TheThe averageaverage AtomicAtomic massmass isis 20.1820.18

Copper,Copper, Cu:Cu: ZZ == 2929 twotwo isotopesisotopes CuCu--6363 69.17%69.17% CuCu--6565 30.83%30.83% At.At. massmass == 63 x 0.6917 + 65 x 0.3083 = == 63.5563.55 a.m.ua.m.u.. ELEMENTS & PERIODIC TABLETABLE

To each , besides a symbol, two numbers are associated: atomic number (Z) - position in the Table (element ID#) mass number (A)

Mass Symbol number 5959

Atomic number 2727 means cobalt (Z=27) atom with its mass number A=59 SUBATOMICSUBATOMIC PARTICLESPARTICLES Although atoms are not destroyed, or disappear in chemical rxns, they have their inner structure: atom consist of 3 types of subatomic particles, with their known electrical charges & masses. mass charge p+ 1 +1 n 1 0 ELECTRON e- 0 -1 (1/2000) Masses are in ATOMIC MASS UNITS (amu) „ ProtonsProtons && neutronsneutrons areare heavyheavy particlesparticles constitutingconstituting atomicatomic nucleus.nucleus. „ TheThe massmass ofof atomatom isis duedue toto nucleusnucleus whichwhich isis veryvery smallsmall inin sizesize && positivelypositively charged.charged. „ ThatThat chargecharge isis thethe atomicatomic numbernumber..

ATOMICATOMIC NUMBERNUMBER ZZ isis thethe NUMBERNUMBER ofof PROTONSPROTONS inin thethe NUCLEUSNUCLEUS

MASSMASS NUMBERNUMBER AA isis thethe SUMSUM ofof PROTONSPROTONS && NEUTRONS,NEUTRONS, i.e.i.e. AA == ZZ ++ nn Electrons are almost weightless & spread around the nucleus. The size of atom is the size of its electron cloud.

Electron cloud: No mass, negative charge Outer () electrons

Atomic nucleus: & neutrons Positive charge = Inner shell number of protons, (core) electrons mass = sum of protons & neutrons ChemicalChemical propertiesproperties (i.e.(i.e. abilityability toto undergoundergo chemicalchemical rxnsrxns)) dependdepend onon thethe electronelectron configurationconfiguration (primarily on the # of e-), which itself is equal to the number of pp+ in a neutral atom (but not related to the number of neutrons) ∴∴ atomsatoms withwith thethe samesame numbernumber ofof pp+ (i.e.(i.e. samesame Z,Z, ∴∴ alsoalso thethe samesame numbernumber ofof ee-)) butbut differentdifferent numbernumber ofof nn areare chechemmicallyically indistinguishableindistinguishable,, eveneven thoughthough theirtheir massesmasses differ.differ.

Atoms with the same Z (number of protons or nuclear charge) but different number of neutrons (∴ different masses) are ISOTOPES 10 Ne Neon,Neon, NeNe:: 33 isotopes:isotopes: 20.18 ZZ AA nn 20NeNe 90.51%90.51% 1010 2020 1010 21NeNe 0.21%0.21% 1010 2121 1111 22NeNe 9.22%9.22% 1010 2222 1212 TheThe averageaverage atomicatomic massmass A=A= 20.1820.18 29 Copper,Copper, Cu:Cu: 22 isotopesisotopes Cu 63.55

ZZ AA nn 63CuCu 69.17%69.17% 2929 6363 3434 65CuCu 30.83%30.83% 2929 6565 3636

AA == 6363××0.69170.6917 ++ 6565××0.30830.3083 == 63.5563.55 amuamu „ IsotopesIsotopes belongbelong toto thethe samesame elementelement,, havehave thethe samesame symbolsymbol,, occupyoccupy thethe samesame cellcell inin thethe PeriodicPeriodic Table,Table, && havehave thethe samesame chemicalchemical properties.properties. „ ““ISOTOPEISOTOPE”” translatestranslates asas ““samesame placeplace””,, i.e.i.e. thethe samesame cellcell inin PeriodicPeriodic Table.Table. „ MassMass numbernumber ofof eacheach isotopeisotope isis anan integerinteger numbernumber (number(number ofof protons)protons) „ NaturalNatural elementselements areare mixturesmixtures ofof isotopesisotopes.. „ AtomicAtomic massesmasses inin thethe TableTable areare notnot integerinteger:: theythey areare averageaverage outout ofof allall thethe naturalnatural isotopesisotopes ofof anyany particularparticular elementelement elements not yet elements not yet several several

groups. groups. (8 after the discovery of noble (8 after the discovery of noble , 1869 arranged all known , 1869 arranged all known – –

predicted predicted Periodic Table advised to look for them. advised to look for them. predicted, very precisely, their properties: predicted, very precisely, their properties: 18 for heavier elements) 18 for heavier elements) & & Mendeleev Mendeleev & & , , in columns in columns (60 by his time) elements according to their increasing atomic masses & noticed some pattern: Properties of elements repeat each other with a they were later discovered in the nature, just where Mendeleev He organized the list of elements as a chart, so that gases, Dmitry He successfully (60 by his time) elements according to their increasing atomic masses & noticed some pattern: Properties of elements repeat each other with a they were later discovered in the nature, just where Mendeleev He organized the list of elements as a chart, so that gases, Dmitry of 7 elements period of 7 elements elements with similar properties stand under each elements with similar properties stand under each other other He successfully known known 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 IA VIIIA

IIA IIIA IVA VA VIA VIIA PERIODIC TABLE OF ELEMENTS

IIIB IVB VB VIB VIIB VIIIB IB IIB „ HorizontalHorizontal rowsrows areare 77 PERIODSPERIODS.. „ VerticalVertical columnscolumns areare 1818 GROUPSGROUPS.. „ TallTall columns:columns:

88 MAINMAIN GROUPGROUPSS (I(IA toto VIIIVIIIA).). „ TheirTheir elementselements areare REPRESENTATIVEREPRESENTATIVE ELEMENTS.ELEMENTS. „ ShortShort columns:columns: TRANSITIONTRANSITION METALSMETALS (Numbered(Numbered asas 33 toto 1212 oror IBIB toto VIIIB)VIIIB) „ TwoTwo cellscells containcontain LANTHANIDELANTHANIDE && ACTINIDEACTINIDE familiesfamilies (which(which areare bothboth INNERINNER--SHELLSHELL TRANSITIONTRANSITION ).METALS). METALSMETALS vs.vs. NONMETALSNONMETALS MostMost ofof elementselements areare metalsmetals:: theythey conductconduct electricity,electricity, heatheat,, areare malleable,malleable, easilyeasily releaserelease theirtheir electronselectrons producingproducing negativenegative ionsions whilewhile formingforming compoundscompounds withwith nonnon--metalsmetals.. Example: Zn combines with non-metal sulfur S: Zn -2e- → Zn2+ S + 2e- → S2-

Almost all metals are solid (except , Hg). of of from from ZnS ZnS upper right corner upper right corner → →

accept electrons accept electrons ) or solids (, , ) or solids (carbon, iodine, 2 2 metals: metals: - - are in the are in the 2+ 2+ 2 2 - - 2 2 Zn Zn S S SO SO → → → → → → - - - - 2 2 2e 2e - - , sulfur, etc.) They do not conduct electricity. metals, but also form compounds with other non the table. They exist as gases, liquids (as , Br phosphorus, sulfur, etc.) They do not conduct electricity. metals, but also form compounds with other non the table. They exist as gases, liquids (as bromine, Br Net reaction is: Zn + S Net reaction is: Zn + S They more likely S + O S + 2e Zn They more likely S + O Nonmetals S + 2e Zn BetweenBetween metalsmetals && nonmetalsnonmetals areare semimetalssemimetals oror metalloidsmetalloids.. TheyThey areare brittlebrittle solidssolids && semiconductorssemiconductors (such(such asas SiSi,, GeGe).). DiatomicDiatomic gases:gases:

HH2,, OO2,, NN2,, FF2,, ClCl2 && twotwo otherother diatomicsdiatomics:: BrBr2((ll),), II2((ss).).

TwoTwo liquidliquid elements:elements:

HgHg && BrBr2 In Periodic Table: „ Each contains elements with similar properties. „ Within a group, metallic properties increase from top to bottom, while non-metallic properties decrease. „ Some groups have their special names: „ 1st group (left column, IA), besides hydrogen, consists of alkaline metals – most active metals In chemical rxns, they always lose 1 electron: Na → Na+ + e- neutral atom positively charged ion (cation) „ 2nd group (IIA) is alkaline earth metals always lose 2 electrons: Ca → Ca+ + 2e- „ Groups 3 to 12 are all transition metals „ 16th group (VIA) is . „ 17th group is (VIIA) - most active non-metals readily accept electron: Cl + e- → Cl- neutral atom negative ion (anion) „ 18th group (right column, VIIIA) is noble gases – non-reactive elements.