Chemistry Year 11 study notes, Study notes of Chemistry

Download Chemistry Year 11 study notes and more Study notes Chemistry in PDF only on Docsity! 1¥ ~ ← WINTRY study notes Module 1 Etf 1¥ CHEM Mahuni Mitvy Properties of Matter Inquiry question: How do the properties of substances help us to classify and separate them? Students: '* explore homogeneous mixtures and heterogeneous mixtures through practical investigations: — using separation techniques based on physical properties (ACSCH026) — calculating percentage composition by weight of component elements and/or compounds: (ACSCHO07) ‘* investigate the nomenclature of inorganic substances using Intemational Union of Pure and Applied Chemistry (IUPAC) naming conventions classify the elements based on their properties and position in the periodic table through their: — physical properties — chemical properties ® Separation Diagrams beaker water containing clear water """ """ - """" """"""1- clamp insoluble solid solvent filter paperresidue ¥ fitter funnel evap. ¥ Vapour dish solution gauze relieving mat container . ! , ' ; ' . tripod -0 . : :-.- . ! . filtrate bunsen settled impurities * ⇒ sedimentation evaporation filtration mixture of iron magnet filings and other thermometer grains Cork stand water out clamp iron water condenser container-9 . " " 1- ⇒ E.) G e I ±. § beaker water in fir tripodbunsen magnetic separation Distillation larger sediment iÉ chromatography paper " " it /MEEEE ' . . . falling smaller - gÉ}:÷Éparticles• . @ e- = I - bowl potinn it:÷÷: fine acetone particles eg sand sieving chromatography paper Atomic structure and atomic mass Inquiry question: Why are atoms of elements different from one another? Students’ ‘+ investigate the basic structure of stable and unstable isotopes by examining: their position in the periodic table — the distribution of electrons, protons and neutrons in the atom representation of the symbol, atomic number and mass number (nucleon number) & model the atom’s discrete energy levels, including electronic configuration and spdf notation (ACSCHO17, ACSCHO18, ACSCHO20, ACSCHO22) & © calculate the relative atomic mass from isotopic composition (ACSCH024) @& Hl investigate energy levels in atoms and ions through: collecting primary data from a flame test using different ionic solutions of metals (ACSCHO19) & ‘examining spectral evidence for the Bohr model and introducing the Schrédinger model investigate the properties of unstable isotopes using natural and human-made radioisotopes as examples, including but not limited to: — types of radiation types of balanced nuclear reactions Nuclear Chemistry The Nucleus mass number (Pt and \ , gyy symbol of the element n°1 ' comprised of protons and neutrons Z ' relative mass of the Atom = protons + neutrons / atomic number' atomic number (2) = the number of protons ( pt ) Isotopes some atoms of the same element have different masses due to different numbers of neutrons in those atoms . Radioactivity It is not uncommon for an element to be unstable , or radioactive . → ' radioisotopes ' stability is based on the ratio of neutrons and protons in the nucleus . Although most nuclei are stable , some are unstable and spontaneously decay, emitting ionising radiation . Types of radioactive decay alpha particle emission : loss of a helium nucleus → heavy nuclei tend . . . alpha emission beta emission → neutron splits into a proton and electron Whic spits out Relative Atomic Mass The relative atomic mass on the periodic table is an average of relative isotopic masses of an element for example , only a tiny fraction of carbon atoms have a mass number of 13 or 14. All the rest have a mass number of 12 . So , the average mass of carbon atoms is 12.01 . This is called the relative atomic mass of carbon . another example : the most common isotope of chlorine is " CI . But about a quarter of all chlorine atoms are a different isotope " CI . Because this is quite a high proportion , the relative atomic mass of chlorine is not a whole number - it is actually 35.5 CALCULATING RELATIVE ATOMIC MASS example : CI - 35 and CI - 37 step 1- multiply mass number of each isotope by its abundance 75×35=2625 and 25×37=925 step 2- add both these values together 2625 t 925 = 3550 step 3- divide by 100 to get the average 3550/100=35.5 Radioisotopes relevance • isotopes that are stable do not emit radiation from the nucleus • Out of about 2000 isotopes , only 279 are stable • most isotopes are unstable and emit radiation as they spontaneously release energy or decay • these are called radioisotopes or radionuclides • some very quick / slow decay Boiling Point Us Atomic number / Fluorine , Chlorine , Bromine , Iodine ) 230 ) 200 - I o• 170 - 140 - 110 - 80 - Br 80 SO - É zo - É .io . or s CI jÉ •= ' - 40 - - 70 - - 100 - - 130 - - 160 - F - 190 - • f- if i 's Lo z 's 3d 3 's 48 y 's sd is Atomic number Models of Atoms Electron excitement → electron can be given extra energy and so be raised from its ground state to an excited state → when electrons in an excited state fall back to their ground state, energy is released in the form of UV , visible and infrared radiation → When this radiation is analysed with a spectroscope , the observed pattern of lines / wavelength ) is called an emission spectrum of the element ( a set of bright or coloured lines on a black background.) Flame tests Visually determines an unknown metal or metalloid by a distinctive colour flame for different metals . Uses electron excitement History of the atom BOHR THEORY • considered electrons as particlesorbitingthe nucleus . Successful in predicting the hydrogen spectrum , failed complicated ones . SCHRODINGER MODEL ground state = lowest energy I v1 ' treated electrons as waves excited state = a higher energy lvl • showed that electrons move at extremely high speeds randomly throughout volumes of space around the nucleus . called orbitals EE ' much more successful at interpreting 8 : atomic and molecular properties. I jÉ The Periodic table of elements molybdenum element name• the periodic table is an ordered 42 atomic number 1 protons ) compilation of all known elements atomic symbol 95.94 atomic mass Elements vs Compounds • elements are pure substances that cannot be chemically or physically Metals , Metalloids , nonmetals decomposed uneven chunks of the periodic table that share similar ' compounds are pure substances physical properties that are chemical combinations of → metals : good conductors , malleable and ductile , usually two or more different elements - have a silvery shine and are usually solid at room temp they can be decomposed → nonmetals : usually good insulators , brittle , usually dull many are gases at room temp , some liquid some solid Periods → Metalloids : properties of both metals and nonmetals , - rows of the periodic table can be made to conduct electricity - increase in atomic number left -0 - right Families - named groups with more specific qualities - corresponds to number of alkali metals : group 1 (one valence electron ) electron shells of elements in ° physical properties : soft , lustrous metallic solids , low density , that period very conductive , low melting point salts ° chemical : highly reactive ( esp . w/ water d oxygen) , present as 1 alkaline earth metals : group 212 valence )Groups (thermal I electric) - columns 0 physical : lustrous metallic solids , conductive , more dense , - elements in the same group higher melting point , harder than alkali metals share similar chemical properties, ° chemical : reactive , oxidise easily , exothermic reaction w/ water same number of valence electrons transition metals : group 3- 12 , vary valencies eg . Group 1/7 01 valence electron , 0 physical : White , hard , lustrous, dense metallic solids , conductive , so highly reactive, us g. 8 who have high melting points a full shell / unreactive) o chemical : less reactive , other properties vary The Periodic table of elements ( cont ) halogens : group 17 , all elements have 7 valence electrons 0 physical : nonmetals , melting and boiling points increase going down the column , change state going down the column (T - - gas , to = liquid . ¥ -- solid ) , poor conductivity , unpleasant odours, very toxic 0 chemical : highly reactive , form ions w/ - I charge , diatomic molecules called noble gases due Noble gases : group 18 , all elements have full Valencies to their tendency not to be provoked into 0 physical properties : gases, low boiling point, low density reaction : ' turning up their nose at a commoner ' as a 0 Chemical : highly unreactive , mostly present as monatomic gases , very noble might do rarely ( almost never ) form compounds PERIODICITY (PERIODIC TABLE TRENDS) Three main periodic properties : Atomic Radius , Ionisation energy . Electronegativity Periodicity 3 main trends : Atomic radius , Ionisation energy , electronegativity Atomic radius nisation energy electronegativity Half the distance between the The energy required to remove one The measure of an ability of centres of two atoms of an valence electron from a gaseous an atom to attract electrons for element that are touching atom chemical bonding → increases right to left → more strongly bound = more energy → smaller atomic radius = → alkali metals have the required ; smaller radii = Valence electrons are more largest radius , increasing more strongly bound close to the nucleus = atom toward the bottom → ionisation energy increases can easily pull external elect - Because left → right there are as atomic radii decreases vous to it the same amount of electron → 1st Ionisation energy : → as atomic radius decreases shells but more protons so energy required to move electronegativity increases electrons are more attract - the first electron /2nd = , high electronegativity = ed to the nucleus and going 2nd electron etc ) ionic bond ; low = more Cova - down the table there are more → low 1st ionisation energy lent shells which expands the = metal radius → high 1st ionisation = utym " """ " " nonmetal → more energy required each time because the ratio between protons I1-1 It electrons gets shewed " NITE * (noble gases = very high) Atomic Radius ttst Ionisation) (2nd ionisation) affects all other ✗ → ✗ + + c- ✗ + →✗2++5 properties Bonding Inquiry question: What binds atoms together in elements and compounds? Students: ‘* investigate the role of electronegativity in determining the ionic or covalent nature of bonds between atoms & ‘* investigate the differences between ionic and covalent compounds through: — using nomenclature, valency and chemical formulae (including Lewis dot diagrams) (ACSCHO29) — examining the spectrum of bonds between atoms with varying degrees of polarity with respect to their constituent elements’ positions on the periodic table — modelling the shapes of molecular substances (ACSCH056, ACSCH057) ‘© investigate elements that possess the physical property of allotropy & ‘© investigate the different chemical structures of atoms and elements, including but not limited to: = ionic networks — covalent networks (including diamond and silicon dioxide) — covalent molecular = metallic structure ‘© explore the similarities and differences between the nature of intermolecular and intramolecular bonds and the strength of the forces associated with each, in order to explain the: — _ physical properties of elements — physical properties of compounds (ACSCH020, ACSCH055, ACSCH058) & IONIC VS COVALENT Ionic : from the electrostatic attraction between oppositely charged ions in a chemical compound → the valence electrons of one atom are transferred permanently to another atom . eg . NaCl covalent : the sharing of an electron pair between two atoms → stable balance of attractive and repulsive forces between atoms Bonding Types Forming compounds . non - metal → gains electrons and forms a negative ' atoms of elements bond together w/ outer e- ion (high electronegativity ) - outer electrons = valence electrons example - type of bonding depends on elements involved An electron from Na is transferred to CI . This causes a & difference in electronegativity charge imbalance in each atom . The Na becomes (Nat ) and the C1 becomes (( I -1 , charged particles or ions The ionic compound is a big lattice - like structure . The ions ' stich ' together because the ions have opposite charges as so are attracted by electrostatic attraction . Form crystals . Chemical formula for ionic compounds shows the ratio of each atom present in the compound . What drives a reaction ? summary ' atoms ' wants the same number of electrons as noble gases → ionic formulas are formed from positive and negative ions → stable electron configurations ( 8 in outer shell ) → positive ions are formed by metals that lost electrons • atoms can lose or gain electrons on their valence shell to get → negative ions are formed by non - metals that gained a full shell electrons → this means atoms in these compounds are no longer neutral → the overall charge of ionic compounds must equal zero but are charged - known as ions COVALENT COMPOUNDS IONIC BONDING - non - metals also form compounds by bonding to each • usually formed between a metal element and a non - other → have different properties to ionic metal element → electrons are shared between atoms • metal → loses its outer electrons and form a positively → electronegative - ties are closer together charged ion low electronegativity ) → molecules , not lattice structures Intermolecular forces Dipole - Dipole polar molecule = dipole → separation of charges → relatively weak → Hoo of intramolecular → stronger with more polar molecules → stronger = higher boiling point tlydrogenbonds → special dipole - dipole force → need specific conditions → OFN : oxygen , fluorine , nitrogen → requires a lone pair of OFN in a neighbouring molecule (OFN because small and electromagnetic) → 10x stronger than dipole - dipole Dispersion → always some dispersion forces → temporary dipole created by chance → destroyed and reformed many times → electrons are constantly in motion ion - dipole forces 3 factors : size and shape → electrostatic attraction between an ion and a molecule that has a - size : more electrons = easier to dipole make a dipole → common in solutions - shape : more effective bonding when linear Chemical structures IONIC NETWORK Ionic compounds form lattice structures , where each cation is surrounded by 6 anions , and each anion is surrounded by 6 cations , - forming something like a cube line NaCl does : Although sodium only gives an electron to one chlorine , the attraction is equal in all directions , so the bond is non - directional • this makes the bonds very strong , so ionic compounds have high melting and boiling points A single molecule of an ionic compound cannot exist , they always exist in lattices - so they are referred to as Formula Units instead of molecules , and are always in the simplest ratio Two methods of electrical conductivity : movement of electrons or the movement of ions • solid : poor electrical conductivity - no free electrons because they are locked into the oppositely charged atoms and ions are stuck in a lattice structure ' Molten : good conductivity - application of heat energy breaks the lattice , so the ions can move more and conduct electricity • aqueous ionic substances : very good electrical conductivity , as the solid dissociates into its ions , they have a large and easy range of movement to conduct electricity Ionic solids are britte (break upon impact) when an impact displaces some of the lattice layers , two or more of the same ion may align . Since they have the same charge , the ions that are in line repel each other , and the solid breaks Chemical structures COVALENT MOLECULAR Sometimes , covalent compounds exist as discrete molecules , with weak intermolecular forces between each molecule Depending on the strength of the intermolecular , covalent molecular compounds can be liquids , solids , gases - thus , they have a wide range of melting and boiling points . Covalent molecular substances do not conduct electricity because there are no ions or free floating electrons COVALENT NETWORK Can come as 2D or 3D networks - most prominent eg : Graphite (2D) vs Diamond (3D) - both carbon allotropes , have different structures → diff . properties • graphite : stacked layers of carbon in a 2D hexagonal lattice structure . Within the layers, there are strong covalent bonds , but between there are weak intermolecular forces (layers slide easily) /why graphite is used in pencils , or solid lubricant) - diamond : tetrahedral , strong covalent bonds everwhere . Very hard, not malleable/ conductive , high melting and boiling points METALLIC A lattice of positive metal ions are held together by a sea of de localised electrons in metal lattices ' de localised electrons carry electricity very well, making metals great conductors of electricity • carry heat energy (kinetic/ by moving around and hitting the cooler parts of the lattice , making metals great conductors of heat • malleable , ductile due to de localised electrons (metal ions displaced, electron cloud acts like ' glue ' and stops ions from repelling and breaking apart