Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
IB Topic 3: Periodicity 3.1: The periodic table • 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. • 3.1.2 Distinguish between the terms group and period. • 3.1.3 Apply the relationship between the electron arrangement of elements and their position in the periodic table up to Z = 20. • 3.1.4 Apply the relationship between the number of electrons in the highest occupied energy level for an element and its position in the periodic table. 1 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. Development of the Periodic Table • Johan Dobereiner Grouped similar elements into groups of 3 (triads) such as chlorine, bromine, and iodine. (1817-1829). • John Newlands Found every eighth element (arranged by atomic weight) showed similar properties. Law of Octaves (1863). • Dmitri Mendeleev Arranged elements by similar properties but left blanks for undiscovered elements (1869). 2 Dmitri Mendeleev 1834 – 1907 • Russian chemist and teacher • given the elements he knew about, he organized a “Periodic Table” based on increasing atomic mass (it’s now atomic #) • he even left empty spaces to be filled in later At the time the elements gallium and germanium were not known. These are the blank spaces in his periodic table. He predicted their discovery and estimated their properties. 5 Henry Moseley 1887 – 1915 • arranged the elements in increasing atomic numbers (Z) – properties now recurred periodically Design of the Table • Groups are the vertical columns. – elements have similar, but not identical, properties • most important property is that they have the same # of valence electrons • valence electrons- electrons in the highest occupied energy level • all elements have 1,2,3,4,5,6,7, or 8 valence electrons IB prefers this one. 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. 3.1.2 Distinguish between the terms group and period. Development of the Periodic Table • Henry Mosley Arranged the elements by increasing atomic number instead of mass (1913) • Glen Seaborg Discovered the transuranium elements (93102) and added the actinide and lanthanide series (1945) Elements arranged by increasing atomic number into • periods (rows) and • groups or families (columns), which share similar characteristics 11 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. Metals • Left side of the periodic table (except hydrogen) • Good conductors of heat and electricity • Malleable: capable of being hammered into thin sheets • Ductile: capable of being drawn into wires • Have luster: are shiny • Typically lose electrons in chemical reactions 12 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. Metals • Alkali metals: Group 1 (1A) • Alkaline earth metals: Group 2 (2A) • Transition metals: Group B, lanthanide & actinide series 13 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. Nonmetals • • • • Right side of the periodic table Poor conductors of heat and electricity Non-lusterous Typically gain electrons in chemical reactions • Halogens: Group 17 (7A) • Noble gases: Group 18 (0) 14 3.1.1 Describe the arrangement of elements in the periodic table in order of increasing atomic number. Metalloids • Between metals and non-metals, along the stair step (except aluminum) • Have properties of metals and nonmetals • Some are semi-conductors • Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Astatine (At) 15 Green = Metals Blue = Metalloids Yellow = Nonmetals http://www.windows2universe.org/earth/geology/metals.html 16 • B is 1s2 2s2 2p1; – 2 is the outermost energy level – it contains 3 valence electrons, 2 in the 2s and 1 in the 2p • Br is [Ar] 4s2 3d10 4p5 How many valence electrons are present? Classification of the Elements 18 19 4f 5f 20 ns2np6 ns2np5 ns2np4 ns2np3 ns2np2 ns2np1 d10 d5 d1 ns2 ns1 Ground State Electron Configurations of the Elements Electron Arrangement Core Electrons: electrons that are in the inner energy levels Valence Electrons: electrons that are in the outermost (highest) energy level 21 3.1.4 Apply the relationship between the number of electrons in the highest occupied energy level for an element and its position in the periodic table. Arrangement of the Periodic Table • Valence Electrons: electrons in the outermost (highest) energy level – – – – – Group 1 elements have 1 v.e.s Group 2 elements have 2 v.e.s Group 3 elements have 3 v.e.s So on and so forth Group 8 have 8 v.e. (except for helium, which has 2) 22 Lewis Dot-Diagrams/Structures • valence electrons are represented as dots around the chemical symbol for the element Na Cl 2 1 3 2 5 8 3.1.4 Apply the relationship between the number of electrons in the highest occupied energy level for an element and its position in the periodic table. Electron dot diagrams Group 1A: 1 dot X Group 5A: 5 dots X Group 2A: 2 dots X Group 6A: 6 dots X Group 3A: 3 dots X Group 7A: 7 dots X Group 4A: 4 dots X Group 0: 8 dots (except He) X 26 Look, they are following my rule! Electron Dot Diagram Using the symbol for the element, place dots around the symbol corresponding to the outer energy level s & p electrons (valence electrons). Will have from one to eight dots in the dot diagram. Draw electron dot diagrams for the following atoms H Be H Be O Al Ca Zr O 28 Electron Dot Diagram Using the symbol for the element, place dots around the symbol corresponding to the outer energy level s & p electrons. Will have from one to eight dots in the dot diagram. Draw electron dot diagrams for the following atoms Al Ca Zr Al Ca Zr 29 2.3.4 Deduce the electron arrangement for atoms and ions. Write electron configuration, orbital filling diagrams, and electron dot diagrams. Kr Tb 30 3.1.3 Apply the relationship between the electron arrangement of elements and their position in the periodic table. Arrangement of the Periodic Table • Group = Sum of electrons in the highest occupied energy level (s + p) = Number of valence electrons 31 3.1.3 Apply the relationship between the electron arrangement of elements and their position in the periodic table. Arrangement of the Periodic Table • Na = 1s22s22p63s1 • Since the sum of electrons in the highest occupied energy level is 1, it will be in the 1st group and have 1 valence electron 32 3.1.3 Apply the relationship between the electron arrangement of elements and their position in the periodic table. Arrangement of the Periodic Table • Na = 1s22s22p63s1 • It is in the 1st group because it has 1 valence electron 33 • B is 1s2 2s2 2p1; – 2 is the outermost energy level – it contains 3 valence electrons, 2 in the 2s and 1 in the 2p • Br is [Ar] 4s2 3d10 4p5 How many valence electrons are present? • Periods are the horizontal rows – do NOT have similar properties – however, there is a pattern to their properties as you move across the table that is visible when they react with other elements 3.1.3 Apply the relationship between the electron arrangement of elements and their position in the periodic table. Arrangement of the Periodic Table • Period = The highest occupied energy level = number of energy levels 36 3.1.3 Apply the relationship between the electron arrangement of elements and their position in the periodic table. Arrangement of the Periodic Table • Na = 1s22s22p63s1 • Sodium is in the 3rd period because it has 3 energy levels The highest occupied energy level is 3 37 IB Topic 3: Periodicity 3.2: Physical properties • 3.2.1 Define the terms first ionization energy and electronegativity. • 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points for the alkali metals (Li Cs) and the halogens (F I). • 3.2.3 Describe and explain the trends in atomic radii, ionic radii, first ionization energies and electronegativities for elements across period 3. • 3.2.4 Compare the relative electronegativity values of two or more elements based on their positions in the periodic table. 38 Periodic Trend Definitions • Atomic Radius: half the internuclear distance between two atoms of the same element (pm) • Ionic radius: the radius of an ion in the crystalline form of a compound (pm) 39 Periodic Trend Definitions • First ionization energy: The energy required to remove one electron from each atom in one mole of gaseous atoms under standard thermodynamic conditions (kJ mol-1) • Electron Affinity: The energy released when one electron is added to each atom in one mole of gaseous atoms under standard thermodynamic conditions (kJ mol-1) 40 Periodic Trend Definitions • Electronegativity: a measure of the tendency of an atom in a molecule to attract a pair of shared electrons towards itself • Melting Point: the temperature at which a solid becomes a liquid at a fixed pressure (degrees Kelvin) 41 Trends in the table IB loves the alkali metals and the halogens • many trends are easier to understand if you comprehend the following • the ability of an atom to “hang on to” or attract its valence electrons is the result of two opposing forces – the attraction between the electron and the nucleus – the repulsions between the electron in question and all the other electrons in the atom (often referred to the shielding effect) – the net resulting force of these two is referred to effective nuclear charge This is a simple, yet very good picture. Do you understand it? 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points Group 1A: Alkali Metals • • • • • Have 1 valence electron Shiny, silvery, soft metals React with water & halogens Oxidize easily (lose electrons) Reactivity increases down the group Group 7A: Halogens • • • • Have 7 valence electrons Colored gas (F2, Cl2); liquid (Br2); Solid (I2) Oxidizer (gain electrons) Reactivity decreases down the group 45 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points Atomic Radii • The radius of an atom, measured in pm (picometers) • Periodic trend (Period 3 Trend) – Atomic size decreases as you move across a period. – The increase in nuclear charge increases the attraction to the outer shell so the outer energy level progressively becomes closer to the nucleus • Group trend for Alkali metals & Halogens – Atomic size increases as you move down a group of the periodic table. – Adding higher energy levels 46 47 Atomic Radii 48 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points Ionic Radii The radius of the ion form of atoms (cations and anions) • Positive ions are smaller than their atoms. • Negative ions are larger than their atoms • Periodic trend (Period 3 Trend) • Group trend for Alkali metals & Halogens – Ions get larger down a group – More energy levels are added – – – – – – Fewer electrons so nucleus attracts remaining electrons more strongly One fewer energy level since valence electrons removed. More electrons so nucleus has less attraction for them Greater electron-electron repulsion Decrease as you move across a period, then spike and decrease again This increase in nuclear charge increases the attraction to the outer shell so the outer energy level progressively becomes closer to the nucleus 49 51 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points First Ionization Energies The energy required to remove the first electron from a gaseous atom. Second ionization removes the second electron and so on. Can be used to predict ionic charges. • Periodic Trend (Period 3 Trend) • Group trend for Alkali metals & Halogens – Generally decreases as you move down a group in the periodic table – Since size increases down a group, the outermost electron is farther away from the nucleus and is easier to remove. – Increases as you move from left to right across a period. – Effect of increasing nuclear charge makes it harder to remove an electron. 52 Filled n=1 shell Filled n=2 shell Filled n=3 shell Filled n=4 shell Filled n=5 shell 53 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points Electronegativity Tendency for the atoms of the element to attract electrons when they are chemically combined with atoms of another element. Helps predict the type of bonding (ionic/covalent). • Periodic Trend (Period 3 Trend) – Increases as you move from left to right across a period. – Nonmetals have a greater attraction for electrons than metals & there is a greater nuclear charge that can attract electrons • Group trend for Alkali metals & Halogens – Generally decreases as you move down a group in the periodic table. – For metals, the lower the number the more reactive. – For nonmetals, the higher the number the more reactive. 54 Electronegativity 55 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points Reactivity The relative capacity of an atom, molecule or radical to undergo a chemical reaction with another atom, molecule or radical. • Don’t worry about the periodic trend!!! • Group trend for Alkali metals – Increases as you move down group 1 in the periodic table – Since alkali metals are more likely to lose an electron, the ones with the lowest 1st ionization energy are the most reactive since they require the least amount of energy to lose a valence electron. • Group trend for Halogens – Decreases as you move down group 7 in the periodic table – Since halogens are more likely to gain an electron, the ones with the greatest electronegativity are the most reactive since they are most effective at gaining a valence electron. 56 3.2.2 Describe and explain the trends in atomic radii, ionic radii, first ionization energies, electronegativities and melting points Melting Points The temperature at which a crystalline melts depends on the strength of the attractive forces and on the way the particles are packed in the solid state • Don’t worry about the periodic trend!!! • Alkali Metals: Melting point decreases down the group – Li (181 oC) to Cs (29 oC) – As the atoms get larger the forces of attraction between them decrease due to the type of bonding (metallic) • Halogens: Melting point increases down the group – F2 (-220 0C) to I2 (114 oC) – Weak attractive forces increase as the molecules get larger due to the type of bonding (non-polar covalent) 57 IB Topic 3: Periodicity 3.3: Chemical properties • Discuss the similarities and differences in the chemical properties of elements in the same group. • Discuss the changes in nature, from ionic to covalent and from basic to acidic, of the oxides across period 3. 58 3.3.1 Discuss the similarities and differences in the chemical properties of elements in the same group. Alkali Metals React with water & react with many substances because… They have the same number of valence electrons 59 3.3.1 Discuss the similarities and differences in the chemical properties of elements in the same group. Alkali Metals 2Na(s) + 2H2O(l) 2NaOH (aq) + H2(g) In the reaction of alkali metals and water, all will: • move around the surface of the water, • give off hydrogen gas, • create a basic solution. 60 3.3.1 Discuss the similarities and differences in the chemical properties of elements in the same group. Alkali Metals In the reaction of alkali metals and water, the reactivity will increase down the group because they get better at getting rid of their valence electron (the 1st ionization energy decreases) So, alkali metals lower down will: • React more vigorously • React faster • Give off a flame 61 3.3.1 Discuss the similarities and differences in the chemical properties of elements in the same group. Alkali Metals Reaction with halogens 2M(s) + X2 (g) 2MX(s) where M represents Li,Na,K,Rb, or Cs Where X represents F,Cl,Br, or I 2Na(s) + Cl2(g) 2NaCl(s) Reactivity decreases down the group 62 3.3.1 Discuss the similarities and differences in the chemical properties of elements in the same group. Halogens Halogens are diatomic as gases (two atoms bond together) and called halides when they form ions… These are BrINClHOF Halogens want to get one electron to fill its outer shell. Reactivity decreases down the group because electronegativity decreases Cl2 reacts with Br- and ICl2(aq) + 2Br-(aq) 2Cl-(aq) + Br2(l) Cl2(aq) + 2I-(aq) 2Cl-(aq) + I2(s) Br2 reacts with I- Br2(aq) + 2I-(aq) 2Br-(aq) + I2(s) I2 non-reactive with halide ions 63 Reactivity of Elements… in action Alkali Metals: http://www.youtube.com/watch?v=m55kgy ApYrY Halogens: http://www.youtube.com/watch?v=tk5xwS5b ZMA&feature=related 64 3.3.2 Discuss the changes in nature, from ionic to covalent and from basic to acidic, of the oxides across period 3. Metallic Oxides in Period 3 Sodium oxide: Na2O Magnesium oxide: MgO Aluminum oxide: Al2O3 ionic ionic ionic Metalloid oxide in Period 3 Silicon dioxide: SiO2 covalent Nonmetallic oxides in Period 3 Tetraphosphorus decoxide: P4O10 Sulfur trioxide: SO3 Dichlorine heptoxide: Cl2O7 covalent covalent covalent 65 3.3.2 Discuss the changes in nature, from ionic to covalent and from basic to acidic, of the oxides across period 3. Acidic/Basic Metallic oxides in Period 3 are basic Sodium oxide: Na2O + H2O 2 NaOH Magnesium oxide: MgO + H2O Mg(OH)2 Aluminum oxide: Al2O3 + H2O 2 Al(OH)3 basic basic amphoteric Metalloid oxide in Period 3 is acidic Silicon dioxide: SiO2 + H2O H2SiO3 acidic Nonmetallic oxides in Period 3 are acidic Tetraphosphorus decoxide: P4O10 + 6H2O 4H3PO4 Sulfur trioxide: SO3 + H2O H2SO4 Dichlorine heptoxide: Cl2O7 + H2O 2HClO4 Argon does not form an oxide acidic acidic acidic 66 Terms to Know • • • • • • • Group Period Alkali metals Halogens Ionic radius Electronegativity First ionization energy 67 Periodic Table of Video • http://www.periodicvideos.com/ 68