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Koo Xuan_S04_A1CHEMI Flipbook PDF
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FOUNDATION PHYSICAL SCIENCE 20 22/ 20 23
Chemistry 1 FSPC0 0 14
Na m e : Koo Xua n Ma t rix Num ber : F22SP2224 Sect ion :4
1.1.1 Matter - Any object that has mass and volume - All matter is made of atoms • Element - a substance that cannot be separated into simpler substances Ex : aluminum (Al) , magnesium (Mg) , oxygen (O) • Compound - a substance composed of atoms of two or more elements chemically united in fixed proportion Ex : water (H2O), carbon dioxide (CO2), sodium chloride (NaCl) • Substance - a form of matter that has a definite composition and distinct properties. o A pure subst a nce ha s a const a nt com posit iona nd dist inct propert y Ex : iron, st eel, a nd wa t er o Mixt ure is a com bina t ion of t wo or m ore subst a nces in which t he subst a nces ret a in t heir dist inct ident it ies Hom ogeneous Mixt ures (uniform ) Ex : Sa lt a nd wa t er, Suga r a nd wa t er, Alcohol a nd wa t er Het erogeneous Mixt ures ( va ria ble / not uniform ) Ex : Sa nd a nd wa t er, Suga r a nd sa lt , Ice in wa t er - St a t e of m a t t er • Solid • Liquid • Ga s
1.2.1 Measurements in Chemistry • Accura cy = t he closeness of a m ea surem ent t o it s t rue va lue • Precision = t he closeness of a set of va lues obt a ined from ident ica l m ea surem ent s of a qua nt it y 1.2.2 Significant Figures in Calculations • Significa nt figures = digit s in a m ea sured num ber t ha t include a ll cert a in digit s plus a fina l uncert a in one Rules : All non- zero num bers a re a lwa ys significa nt All zeroes in bet ween non- zero num bers a re a lwa ys significa nt All zeroes t o t he left of t he first nonzero digit a re not significa nt All zeroes which a re sim ult a neously t o t he right of t he decim a l point a nd a t t he end of t he num bers a re a lwa ys significa nt
Application of Stoichiometry Soap, tires, fertilizer, gasoline, deodorant, and chocolate bars are just a few commodities you use that are chemically engineered, or produced through chemical reactions.
1.2 Unit s & Mea surem ent s 1.2.3 Dimensional Analysis • useful for keeping check of ca lcula t ions a nd for convert ing unit s in chem ica l ca lcula t ions
1.1.4 Molecules - a n a ggrega t e of t wo or m ore a t om s (sa m e a t om s or different a t om ) in a specific geom et rica l a rra ngem ent held t oget her by chem ica l forces. - com e in different sha pes a nd pa t t erns 1.1.2 Dalton’s Atomic Theory ⁃ by 180 8 John Dalton ⁃ m a t t er is m a de up of t iny a t om s ⁃ a t om s of t he sa m e elem ent a re ident ica l ⁃ a t om s com bine in definit e ra t ios t o form com pounds ⁃ a t om is neit her crea t ed nor dest royed in chem ica l rea ct ion
1.1.3 Atom/Elements At om - m a de up of suba t om ic pa rt icles - t he sm a llest unit of a n elem ent t ha t ca n exist or t a ke pa rt in a chem ica l rea ct ion - consist s of a nucleus surrounded by elect ron cloud - nucleons consist s of prot ons a nd neut rons - Genera l Sym bol for a n At om is Isot opes - a t om s of t he sa m e elem ent ha ving t he sa m e num ber of prot ons but different num ber of neut rons - different m a sses - undergo t he exa ct sa m e chem ica l rea ct ions - ha ve different physica l propert ies Elem ent s - a t om s m a y be physica lly a t t ra ct ed t o ea ch ot her, but a re not chem ica lly bonded t oget her Molecula r Elem ent s - t he m olecules a re m a de of t wo or m ore a t om s chem ica lly bonded t oget her by cova lent bonds
1.1 Matter CHAPTER 1 Fundamental of Chemistry & Principles of Stoichiometry
1.4 Concent ra t ions of Solut ions
14.1 Units of Concentration Concent ra t ion = a m ount of solut e in a given a m ount of solut ion • Solut ion = Solut e ( a solid subst a nce ) is dissolved in t he solvent ( a liquid) t o form t he solut ion (solva t ion) • Solut ion = dissolving a m ore concent ra t ed solut ion int o t he solvent (dilut ion) • Dilut e solut ions solvent
1.4.2 Volumetric Analysis & Dilution • Dilut ion(used t o det erm ine volum e a nd ca lcula t ing t he m ola rit y of solut ion when perform ing dilut ions) *M1x V1 = M2 x V2 • Acid – Ba se Tit ra t ion(process of m ixing t wo rea ct a nt s t o det erm ine t he equiva lence point of a rea ct ion) *
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1.3 St oichiom et ry 1.3.1 The Mole Concepts & Avogadro Constant Mole = num ber of pa rt icles equa l t o t he num ber of a t om s in 12 g of C- 12 • Avoga dro’s Num ber = 6.0 221421x 10 23 • m ola r m a ss (M) is t he m a ss in gra m s of one m ole of it s ent it ies (g m ol- 1) Mola r Volum e of Ga ses • t he volum e occupied by one m ole of a ny ga s At s.t .p, t he m ola r ga s volum e is 22.4 dm 3 At room t em pera t ure a nd pressure (r.t .p), t he m ola r ga s volum e is 24dm 3 Percent Com posit ion • Percent a ge by m a ss of ea ch elem ent in a com pound
1.1.5 Ions - cha rged a t om s or groups of a t om s • Anions - ga in elect rons - nega t ively cha rged ions - form ed by non- m et a l a t om s Ex : Chloride (Cl- ), Brom ide (Br- ), Sulfa t e (SO42- ) • Ca t ions - lose elect rons - posit ively cha rged ions - form ed by m et a l a t om s Ex : Sodium (Na +), Iron (Fe2+), Am m onium (NH4+)
1.3.2 Chemical Formula • Molecula r form ula : a form ula which describes t he exa ct com posit ion of a m olecule • Em pirica l form ula : a form ula which gives t he sm a llest whole num bers t ha t describe t he ra t ios of a t om s in a subst a nce • St ruct ura l form ula : a form ula which describes t he posit ions of a t om s in a m olecule.
1.3.4 Stoichiometric Calculations • St oichiom et ry is a concept used t o rela t e a nd ca lcula t e weight , m oles a nd percent wit hin a chem ica l equa t ion • St oichiom et ry equa t ion = t he st udy of num erica l rela t ionship bet ween chem ica l qua nt it ies in a chem ica l rea ct ion La w of conserva t ion of Ma ss Ba la ncing equa t ions by ba la ncing a t om s
1.3.3 Balanced Chemical Equations Chem ica l Equa t ions : short ha nd wa y of describing a rea ct ion & provides inform a t ion a bout t he rea ct ion. Ex : C5H12 + O2 - - - >CO2 + H2O C5H12 + 8O2 - - - > 5CO2 + 6H2O
1.3.5 Limiting Reagent • The lim it ing rea ct a nt will be com plet ely used up in t he rea ct ion • The rea ct a nt t ha t is not lim it ing is in excess – som e of t his rea ct a nt will be left over. Theoret ica l a nd Act ua l Yield
Interaction of light and matter •
Electromagnetic radiation
Electron excitation and spectra
- visible and invisible light (or radiation) - travel in waves - defined by their wavelength (λ) a nd frequency (v) Am plitude - t he height of t he wa ve (dist a nce from node t o crest ) Wa velengt h(λ) - a m ea sure of t he dist a nce covered by t he wa ve (t he dist a nce from one crest t o t he next ) Usua lly m ea sured in na nom et ers. (1 nm = 1 x 10 - 9m ) Frequency(v) - t he num ber of wa ves t ha t pa ss a point in a given period of t im e. >Unit s a re hert z (Hz), or cycles/ s = s- 1. (1 Hz = 1 s- 1) Equa t ion 1 : c =λv (c is the speed of light = 3x108 m-s1) • Invisible light (cannot be seen with the naked eye) (γ- rays, X- rays, ultra- violet, Infra- red and microwave) • Visible light(white light, separates into a continuous spectrum of colors) (colored red, orange, yellow, green, blue, indigo, and violet exist at wavelengths ranging between 400 to750 nm) • Continuous spectrum - Light passed through a prism is separated into all its colors.
When elements e ( g Na, He) are used as a source of light, a characteristic line spectrum is observed. • This phenomenon can be explained by the quantum theory (Planck, 1900 and Einstein, 1905) - light is emitted in the form of a ‘discrete’ or definite packet called ‘quantum’ or ‘photon’ (not in a continuous wave) • The frequency of this light, is proportional to the energy, E Equation 2 :ΔE =hv ( h = 6.63 X 10 - 34 J s (h is the Planck constant) • Bohr's atomic theory : Electrons exist in specific energy levels By absorbing a quantum (or photon) of energy (small energy packet with a definite size) an electron is elevated to a higher energy level known as the excited state When the electron falls from its excited state to the ground state of a lower energy level, a quantum of energy is released or emitted (The energy released shows up as a line spectrum) The characteristics of the line spectra is usedto determine the electronic structure of
an atom
Elctronic Structure of Atoms
Chapter 2 Electronic Structure of Atom
Qua nt um num bers • • •
The a t om is divided int o shells a nd subshells Orbit a ls cont a ining elect rons exist wit hin t he subshells A series of 4 qua nt um num bers (n, l, m l a nd m s) a re used t o describe t he loca t ion of elect rons in t hree- dim ensiona l spa ce • The cha ra ct erist ics of t he 4 qua nt um num bers (n, l, m l a nd m s) a re a s follows: n is t he principle qua nt um num ber [Describes t he shell or energy (or qua nt um ) level in which a n elect ron resides] Va lues : Int egers 1,2,3... ∞ (The higher t he va lue of n, t he higher is t he energy of t he shell) l is t he a zim ut ha l (or seconda ry) qua nt um num ber Specifies a subshell in a n a t om Va lues : n- n… up t o…n- 1 m l is t he m a gnet ic qua nt um num ber [Describes t he orient a t ions (or com ponent s) of orbit a ls rela t ive t o ea ch ot her] Va lues : - l … .0 … .+l m s is t he spin qua nt um num ber (Decribes t he direct ion in which t he elect ron spins on it s a xis) Va lues : m s = +1/ 2 is for a n elect ron spinning in a clockwise direct ion m s = - 1/ 2 is for a n elect ron spinning in a n a nt iclockwise direct ion • Only 2 elect rons m a y occupy ea ch one ‘orbit a l orient a t ion’a nd t he elect rons m ust ha ve opposit e spins
Application of Electronic Structure of Atom Allow photosynthesis under process [there would be no light (or color or photochemical reactions) if it were not for electrons]
Quantum Numbers and Electron Configurations Elect ron configura t ion
Bohr atomic model
Bohr’s major idea was that the energy of the atom was quantized, and that the amount of energy in the atom was related to the electron’s position in the atom. o Bohr suggest ed t ha t elect rons : • ha ve specific energy va lues in t he a t om • orbit a bout t he nucleus m uch like t he wa y pla net s orbit t he sun • exist in specific energy levels ca lled shells • a bsorb ‘discret e’qua nt it ies of energy during t ra nsit ions from a lower t o a higher energy level • em it ‘discret e’qua nt it ies of energy during t ra nsit ions from a higher t o a lower energy level In t he Bohr m odel of hydrogen, t he lowest a m ount of energy hydrogen’s one elect ron ca n ha ve corresponds t o being in t he n = 1 orbit . We ca ll t his it s ground state. When t he a t om ga ins energy, t he elect ron lea ps t o a higher energy orbit . We ca ll t his a n excited state . The a t om is less st a ble in a n excit ed st a t e a nd so it will relea se t he ext ra energy t o ret urn t o t he ground st a t e. o Post ula t es • The H a t om ha s only cert a in a llowa ble energy levels ca lled st a t iona ry st a t es a ssocia t ed wit h a fixed circula r orbit of t he elect ron a round t he nucleus. • An elect ron in a perm it t ed orbit ha s a specific energy a nd will not ra dia t e energy. • The a t om cha nges t o a not her st a t iona ry st a t e only by a bsorbing or em it t ing a phot on whose energy equa ls t he difference in energy bet ween t he t wo st a t es. E photon = E final–E initial =hυ o Rydberg equation The wa velengt h, λ of ea ch line is det erm ined by t he equa t ion Equa t ion 3 : The energy, E of ea ch line ca n be det erm ined by t he genera l equa t ion Equa t ion 4 : λ = wa velengt h of a spect ra l line ni a nd nf = posit ive int egers wit h nf > ni R = Rydberg const a nt (1.0 96776 x 10 7 m - 1)
• dist ribut ion of elect rons a m ong t he orbit a ls of a n a t om • wa ys t o indica t e how elect rons a re a rra nged in a n a t om : i. The da rt boa rd : Circles t o represent shells a nd crosses (or dot s) t o represent elect rons ii. The orbit a l dia gra m : Boxes or circles cont a ining a rrows indica t ing elect rons a nd t heir respect ive spins iii. The elect ron configura t ion : List of subshells (a ccording t o t he Aufba u Principle) a nd superscript s represent ing t he num ber of elect rons • Rules for working out t he elect ronic st ruct ure of a t om s a. The Aufba u principle st a t es t ha t orbit a ls should be filled st a rt ing wit h t hose of lowest energy a nd working out wa rds b. The Hund’s rule st a t es t ha t when filling a subshell, ha lf fill ea ch orbit a l before com plet ely filling a ny one subshell c. The Pa uli exclusion principle st a t es t ha t no t wo elect rons in a n a t om ca n ha ve t he sa m e set of qua nt um num bers • Irregula rit ies in t he elect ron configura t ion of t ra nsit ion elem ent s At om s of t ra nsit ion elem ent s such a s Sc, Ti, V, Cr, Mn, Fe, Ni, Cu ha ve pa rt ia lly filled d orbit a l They ha ve irregula r configura t ions (different from t he predict ed one) beca use t hey t end t o shift elect rons t o a cquire a m ore st a ble configura t ion • Ma gnet ic propert y of a n a t om Pa ra m a gnet ic a t oms a re a t t ra ct ed by a m a gnet These a t om s cont a in one or m ore unpa ired elect rons [Unpa ired elect rons ha ve t he sa m e or pa ra llel (↑ ↑ ) spins t o ea ch ot her] Dia m a gnetic a t oms a re repelled by a m a gnet These a t om s cont a in only pa ired elect rons [Pa ired elect rons ha ve opposit e or a nt ipa ra llel spins (↑ ↓ ) t o one a not her] • Va lence Elect rons - The elect rons in a ll t he subshells wit h t hehighest principa l energy shells - Core elect rons - elect rons in lower energy shells.
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The Qua nt um a t om ic m odel
Erwin Schrodinger (1926) derived a set of equa t ions or wa ve funct ions for elect rons • He described t he orbit a ls (elect ron clouds) which a re specific regions in which t here is a la rge proba bilit y of finding elect rons • The wa ve funct ion of ea ch elect ron ca n be described a s a set of four qua nt um num bers: - The principa l qua nt um num ber (n) describes t he energy level of a n elect ron - The Azim utha l qua nt um num ber (l) describes how fa st t he elect ron m oves in it s orbit or t he a ngula r m om ent um - The m a gnet ic qua nt um num ber (m l) is rela t ed t o t he elect rons orient a t ion in spa ce - The spin qua nt um num ber (m s) is rela t ed t o t he direct ion t ha t t he elect ron spins while it is m oving in it s orbit (Only t wo elect rons could sha re t he sa m e orbit a l, one spinning clockwise a nd t he ot her spinning count erclockwise) • The orbit a ls ha ve different sha pes a nd num bers a t a ny different levels
Periodic Physical Properties
Classification of elements •
Classification according to metallic property Metals are located on the left part of the Periodic Table (the metallic property increases from the right towards the bottom left of the Periodic Table) Some are recognized by specific group names - The alkali metals or Group 1Ametals - The alkaline earth metals or Group 2Ametals Non metals are located on the right part (mostly upper right) of the periodic table Some are recognized by specific group names - The Halogens or the Group 7Agases - The Nobel gases or the Group 8Agases Metalloids are located on both sides of the zig-zag lines starting from Boron (B) up to Astatine (At) • Classification according to the outer shell electron configuration (valence electron configuration) Representative elements - s block elements have valence shell electron configurations of ns1and ns2 - p block elements have valence shell electron configurations of ns2 np1up to ns2 np5 - Noble gases have valence shell configurations of ns2 np6 (completely filled p orbitals) Transition elements - d block elements have valence electron configurations of nsx(n-1)dy (where x=1or 2 and y=1to 10) - f block elements have incomplete f orbitals (nf1-nf13) The Lanthanides (incomplete 4f orbitals) Actinides (incomplete 5f orbitals)
Application of Periodic Table Scientists use the periodic table to quickly refer to information about an element, like atomic mass and chemical symbol.
Periodic Chemical Properties
Have similar chemical properties because they have similar valence electron configurations Trends within a group The reactivity and physical properties tend to increase from top to bottom in a group Trends within a period The property may reach a certain peak (from left to right) within a period and then reverse the trend Metals on the left of the period form basic oxides Metals/ non metals on the right form acidic oxides The point of change in the period occurs around Al which can act amphoterically
Parts of the Periodic Table • •
Group (vertical bars ↓ ) : Each group consists of elements that have the same number of valence electrons in their valence (outermost) shells. Period (horizontal bars ↔) : Each period consists of elements that have similar valence shells.
Chapter 3 : Periodic Table 4
Atomic size The atomic radius = ½ of the distance between 2 nuclei of two adjacent atoms = ½d • Neutral atoms • The sizes of atoms increase downwards in a group (Electrons fill up new shells downwards. Outer electrons are shielded from the nucleus by electrons in inner shells and are less tightly held) • The sizes of atoms decrease towards the right across a period [Electrons fill up the same shell, but the effective nuclear charge ( Zeff ) of the atom increases, thus the electrons are held more tightly] The effective nuclear charge, Z eff, is the actual charge felt by an electron - Z is the nuclear charge = atomic number Z eff = Z - σ - σ is the shielding constant = the number of inner shell electrons • Isoelectronic ions - a series of atoms or ions in which the number of electrons are constant • Sizes of the atom/ ion decrease as the number of protons ( Z ) increases • Sizes of ions compared to their parent atoms • The size of cations are smaller than their corresponding parent atoms • The size of anions are larger compared to their corresponding parent atoms Ionization Energy (IE) The first ionization energy is the energy needed to remove 1mole of the outermost electrons from 1mole of neutral atoms in the gas phase General trend: • The 1st IE increases towards the right across a period • The 1st IE decreases downwards in a group Exceptions to the general trend: • The 1st IE of the 3Agroup atoms are smaller than that of the 2Agroup atoms • The 1st IE of the 6Agroup atoms is smaller than the 5Agroup atoms • 2nd and higher ionization energies There is an abrupt increment of IE when an electron is removed from a full noble gas core configuration (ns2 np6) Electron Affinity The electron affinity is the energy involved when 1mole of electrons is gained (accepted) by 1 mole of neutral atoms in the gas phase General trend: • EAbecome less negative (decreases) downwards in the periodic table • EAbecome more negative (increases) towards the right across a period Electronegativity Electronegativityis a measure of the attraction of an atom for the electrons in a chemical bond - Elements with low ionization energies have low electronegativities - Elements with high ionization energies have high electronegativities General trend : • In a group (downwards) the electronegativity decreases • In a period (towards the right) the electronegativityincreases