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
The Periodic Table The Old Table • 1869 – Mendeleev: method of organizing the elements according to both their masses and their properties. • Vertical Columns: Elements arranged in groups each group shares similar properties. • Horizontal Rows: Elements are arranged in periods Mendeleev’s table showed gaps, indicating missing elements (not discovered yet). Why was this important? • The location of missing elements allowed their chemical and physical properties to be predicted. The Modern Periodic Table • Elements arranged by atomic number (not mass) • (eg. K heavier than Ar…..due to isotopes) Periodic Law: “The properties of the elements recur along the rows” (i.e. an element has similar properties to the one below or above it) Division in the Periodic Table • Period: all elements in a given row of the periodic table. • Group or family: all elements in a given column of the periodic table. Rows = Periods Columns = Groups or families Particular groups, rows and blocks of elements Alkali metals group 1 (except hydrogen) Alkaline earth metals group 2 Transition metals block d Representative elements Halogens main group elements, s and p blocks 2nd last group (starts with F) Noble gases last group (these elements have full valence orbitals) Lanthanides row with atomic # 57 → # 71 Actinides below Lanthanides, atomic # 89 → #103 We can also divide P.T. into: Metals, Non-metals and Semiconductors • Elements become more __metallic______ from _right___ to __left_____ across the periodic table and from ___top_____ to _bottom__ of a group. Properties of METALS: • • • • • • shiny. opaque. good conductors of heat and electricity. usually flexible when in sheet form. malleable and ductile. solid at room temp. (except of Hg) Properties of NON-METALS: • gas, liquid, or brittle solids at room temp. • poor conductors of heat and electricity. • solids are not shiny 2 types of Non- metals: • 1. Low electrical conductivities. • 2. Moderate electrical conductivities. Some elements DO share properties of metals and non-metals Semiconductors (metalloids or moderate electrical conductivities ) • non-metal. • electrical conductivity increases when ↑T • eg) B, Si, Ge, As, Sb, Te, At Now You Try!! • Do the following questions with your partner orally (5 min) Homework p. 164 #35-39 Electrostatic Trends in P.T. • from right to left and top to bottom of the Periodic Table – elements become more metallic – atomic radius increases • from left to right and bottom to top of the P.T – electron affinity increases – ionization energy increases – Electronegativity increases Electronegativity Electronegativity Ionization Energy (I.E.) • I.E. is the energy required to remove one or more electrons from a neutral atom in the gas phase • • • • 1st I.E.: The energy required to remove the 1st valence electron 2nd I.E.: The energy required to remove the 2nd valence electron 3rd I.E.: The energy required to remove the 3rd valence electron 4th I.E.: The energy required to remove the 4th valence electron eg) 1st IE: Rb(g) Rb+(g) + e2nd IE: Rb+ (g) Rb2+ (g) + e3rd IE: Rb2+(g) Rb 3+ (g) + e- (∆Hº = 400 kJ/mol) (∆Hº = 580 kJ/mol) (∆Hº = 600 kJ/mol) Explaining I.E.’s 1. The positively charged nucleus attracts the electrons therefore the 1st I.E. of He is approx twice the 1st I.E. of H. This is because H has 1 proton and He has 2. Therefore the IE increases as nucleus size increases 2. Electrons in higher n feel less attraction to the nucleus because electrons in smaller n shield/block the attractive force of nucleus electrons in higher n are easier to remove. Therefore IE decrease as n increases. eg) Which has higher I.E.? a. Na b. Mg c. F or or or Mg Al Cl Now You Try • Do these questions • p. 168 #48, 49 and 51 Electron Affinity (E.A.) • E.A. is the ∆E that occurs when a neutral atom in the gas phase gains an electron. (or how much a neutral atom wants an electron) eg) F (g) + e- F- (g) E.A. increases as atom size decreases because the elecrons added is nearer the nucleus (lower n) the electrons repelled by fewer other electrons Atomic Radius • Atomic radius: distance from center of nucleus to outermost electron 1) Moving down a group, • • • 2) n increases orbital size increases atomic radius increases Moving left to right across a period – – – Number of protons increases orbital size decreases atomic radius decreases eg) Which is smaller? • • • • a) b) c) d) K Rb Sn O or or or or Ca Sb Pb S Now you try!! • Do these questions in your work book • P. 170-171 # 53(a,b,c,d,f) 54, 55(a,b,c,d,f) 56 Electronegativity (E.N.) • E.N. is the tendency of the atom to attract e-s from a neighbouring atom or how strongly an atom pulls on nearby electrons. • E.N. increases as you move from left to right () and from bottom to top(↑) of the P.T. Atoms with high Electronegativity • strongly attracts e-s from nearby atoms • strongly attracts its own valence e-s vice versa also true….. • Atoms with low E.N. – have little attraction for electrons from a nearby atom and for its own electrons • eg) Li and F • Li has low E.N. \gives away an e- easily) • F has high E.N. \attracts e- strongly) • If F and Li are near F takes an e- from Li In the P.T: Moving: Atom’s properties are affected by: Down a family… Increasing atom size and increasing distance between nucleus and valence e-s Across a period…. Differing valence, nuclear charge, and charge on species Chemical Reactivity • How likely or strongly an atom will react with other substances. This is determined by how easily electrons can be removed (ionization energy) and how badly they want to take other atom's electrons (electronegativity). Metals • Period - reactivity decreases as you go from left to right across a period. • Group - reactivity increases as you go down a group • Why? The farther to the left and down the periodic chart you go, the easier it is for electrons to be given or taken away, resulting in higher reactivity. Non-metals • Period - reactivity increases as you go from the left to the right across a period • Group - reactivity decreases as you go down the group. • Why? The farther right and up you go on the periodic table, the higher the electronegativity, resulting in a more vigorous exchange of electrons. Exception • Nobel gases are non reactive Now you try!! • Do these questions in your work book p. 173 #58 – 61