MODULE 3.pdf
Transcript
04/09/2024 1 04/09/2024 2 04/09/2024 Periodic Table Blocks The s Block The p Block The s block includes The p block consists of hydrogen and helium...
04/09/2024 1 04/09/2024 2 04/09/2024 Periodic Table Blocks The s Block The p Block The s block includes The p block consists of hydrogen and helium elements in Group 3A (13) to Group 8A (18). elements in Group 1A (1) elements in Group 2A (2) There are six p block elements in each period, Elements in the s block have because three p orbitals their final one or two can hold up to six electrons in an s orbital. electrons. 3 04/09/2024 The d Block The f Block The d block contains The f block contains inner transition elements, two rows transition elements. at the bottom of the periodic table. The f sublevel is two The d sublevels are less than the period number. one less (n – 1) than the period number. There are 14 elements in each f block, because there are There are 10 elements in each d block, because five d seven f orbitals that can hold up to orbitals can hold up to 10 electrons. 14 electrons. 4 04/09/2024 For Chem 16, we will label the subshells with negative values on the left. In the same way that we fill the positive ms (spin up) electrons first, when filling the orbital from left to right, we fill the negative ml first. -1 0 +1 -2 -1 0 +1 +2 n = 3, l = 1, ml = -1, ms = +1/2 -3 -2 -1 0 +1 +2 +3 5 04/09/2024 n=2 l=1 ml = -1 ms = -1/2 6 04/09/2024 Electron Configurations, Using the Guide to Writing Electron Periodic Table Configurations Using the periodic table, write the electron configuration for silicon. Solution Period 1 1s block 1s2 Period 2 2s → 2p blocks 2s2 2p6 Period 3 3s → 3p blocks 3s2 3p2 (Si) Writing all the sublevel blocks in order gives 1s2 2s2 2p6 3s2 3p2 7 04/09/2024 Sample Problem Sample Problem Use the sublevel blocks on the periodic table to write the Use the sublevel blocks on the periodic table to write the electron configuration for chlorine. electron configuration for chlorine. Step 1 Locate the element on the periodic table. Step 2 Write the filled sublevels in order, going Chlorine (atomic number 17) is in Group 7A across each period. (17) and Period 3. Sample Problem Period 4 Use the sublevel blocks on the periodic table to write the The 4s sublevel fills before the 3d sublevel because the electron configuration for chlorine. electrons in the 4s sublevel are slightly lower in energy Step 3 Complete the configuration by counting the than those in the 3d sublevel. electrons in the last occupied sublevel block. This order occurs again in Period 5, when the 5s fills before the 4d sublevel, and in Period 6, when the 6s fills before the 5d sublevel. The electron configuration for chlorine (Cl) is 1s2 2s2 2p6 3s2 3p5 8 04/09/2024 Period 4 Period 4 Some Exceptions in Sublevel Some Exceptions in Sublevel Block Order Block Order In filling the 3d sublevel, exceptions occur for chromium In Cu the 3d sublevel is close to being filled, which is and copper. more stable; thus one of the 4s electrons moves to the In Cr the 3d sublevel is close to being half-filled, 3d sublevel. which is more stable; thus one of the 4s electrons moves to the 3d sublevel. 4s 3d 4s 3d 9 04/09/2024 Learning Check Solution Use the periodic table to give the symbol of the element Use the periodic table to give the symbol of the element with each of the following electron configurations. with each of the following electron configurations. A. 1s2 2s2 2p6 3s2 3p6 4s2 3d7 A. 1s2 2s2 2p6 3s2 3p6 4s2 3d7 Element is cobalt (Co). B. [Ar] 4s2 3d10 4p5 B. [Ar] 4s 3d10 4p5 2 Element is bromine (Br). 10 04/09/2024 The Periodic Table History of the Periodic Table Antoine Lavoisier (1743 – 1794) – Published Elements of Chemistry in 1789 Included a list of “simple substances” (which we now know to be elements) Formed the basis for the modern list of elements – Only classified substances as metals or nonmetals History of the Periodic Table History of the Periodic Table Johann Döbereiner (1780 – 1849) – Classified elements into “triads” John Newlands (1837 – 1898) Groups of three elements with related – Law of Octaves (1863) properties and weights Stated that elements repeated their chemical properties every eighth element Began in 1817 when he realized Sr was Similar to the idea of octaves in music halfway between the weights of Ca and Ba and they all possessed similar traits – Döbereiner’s triads: Cl, Br, I S, Se, Te Ca, Sr, Ba Li, Na, K 04/09/2024 History of the Periodic Table Dmitri Mendeleev (1834 – 1907) Dmitri Mendeleev (1834 – 1907) – Russian chemist (“The father of the periodic table”) – Arranged elements based on accepted atomic masses and properties that he observed – Listed elements with similar characteristics in the same family/group Left blank spots for predicted elements (Ted-Ed Video) History of the Periodic Table Periodic Law Henry Moseley (1887 – 1915) – English physicist Periodic – occurring at regular intervals – Arranged elements based on increasing atomic – Relates to trends on the periodic table of number elements Remember: atomic number = # of p+ in nucleus Modern Periodic Law – Periodic table looked similar to – When elements are arranged in order of Mendeleev’s design since as increasing atomic number, there is a atomic number increases, so periodic repetition of their properties does the atomic mass Just like Mendeleev suspected!! 04/09/2024 Reading the Periodic Table A Different Type of Grouping Periods - “Horizontal Rows” Groups (or Families) - “Vertical Columns” Besides the 4 blocks (s,p,d,f) of the table, there is another way of classifying element: Metals Nonmetals Metalloids or Semi-metals. Metals Nonmetals Metals are lustrous Nonmetals are the (shiny), malleable, opposite. ductile, and are They are dull, brittle, good conductors of nonconductors heat and electricity. (insulators). They are mostly Some are solid, but solids at room temp. many are gases, What is one and Bromine is a exception? liquid. 04/09/2024 Reading the Periodic Table Metalloids Valence electrons are periodic! Metalloids, aka semi- Notice the similarities metals are just that. – Ex.) Write the noble gas configurations for: They have characteristics F [He]2s22p5 7 valence electrons of both metals and nonmetals. Cl [Ne]3s23p5 7 valence electrons They are shiny but brittle. Br [Ar]4s23d104p5 7 valence electrons And they are I [Kr]5s24d105p5 7 valence electrons semiconductors. What is our most – GROUPS have similar valence electron important semiconductor? configurations! Groups of Elements Groups of Elements Group 1 = Alkali Metals Group 17 = Halogens – Located in Group 1 (except Hydrogen) – Very active nonmetals – Extremely reactive Want to gain 1 e- to become like a noble gas Want to lose 1 e- to become “noble gas-like” Group 2 = Alkaline Earth Metals – Also very reactive – Both Group 1 & 2 occur naturally as compounds not elements 04/09/2024 Groups of Elements Groups of Elements Group 18 = Noble Gases Transition Metals – Sometimes called “inert gases” since they – Located in the center of the Periodic Table generally don’t react – 10 elements wide (“d” orbitals) Mainly true, but not always (Kr, Xe will – Semi-reactive, valuable, crucial to many life react sometimes) processes Have a full valence shell (8 e-) Lanthanides and Actinides – Located at the bottom of the Periodic Table – 14 elements wide (“f” orbitals) – Some are radioactive, though not all – Lanthanides = Period 6 (4f) Mythbusters Noble Gas Demo – Actinides = Period 7 (5f) 04/09/2024 04/09/2024 04/09/2024 Periodic Properties & Trends Periodic Properties & Trends Electronegativity Atomic Radius – Ability of an atom to pull towards itself e- – Distance between the nucleus and the – Increases going up and to the right furthest electron in the valence shell Across a period more protons in nucleus = more positive charge to pull electrons closer – Increases going down and to the left Down a group more electrons to hold onto = Down a group more e- = larger radius element can’t pull e- as closely Across a period elements on the right can pull e- closer to the nucleus (more electronegative) = smaller radius *Remember* – LLLL Lower, Left, Large, Loose 04/09/2024 Periodic Properties & Trends Ionization Energy – Energy required to remove an e- from the ground state – 1st I.E. = removing 1 e-, easiest – 2nd I.E. = removing 2 e-, more difficult – 3rd I.E. = removing 3 e-, even more difficult Ex.) B --> B+ + e- I.E. = 801 kJ/mol Ex.) B+ --> B+2 + e- I.E.2 = 2427 kJ/mol Ex.) B+2 --> B+3 + e- I.E.3 = 3660 kJ/mol Periodic Properties & Trends Ionization Energy Increases going up and to the right – Down a group more e- for the nucleus to keep track of = easier to rip an e- off – Across a period elements on the right can hold electrons closer (more electronegative) = harder to rip an e- off 04/09/2024 04/09/2024 Periodic Properties & Trends Metallic Character – How “metal-like” an element is Metals lose e- – Most Metallic: Cs, Fr – Least: F, O – Increases going down and to the left Think about where the metals & nonmetals are located on the periodic table to help you remember! Periodic Properties & Trends Ionic Radius – Radius of an atom when e- are lost or gained different from atomic radius – Ionic Radius of Cations Decreases when e- are removed – Ionic Radius of Anions Increases when e- are added 04/09/2024 Sizes of Ions Sizes of Ions + - Li,152 pm Li + , 78 pm F, 71 pm F- , 133 pm 3e and 3p 2e and 3 p 9e and 9p 10 e and 9 p CATIONS are SMALLER than the ANIONS are LARGER than the atoms atoms from which they are formed. from which they are formed. Size decreases due to increasing he Size increases due to more electrons in shell. electron/proton attraction. Overall Periodic Trends Property Group Trend Period Trend Increases going Increases to the left Atomic Radius down Increases going up Increases to the Ionization Energy right Increases going up Increases to the Electronegativity right Increases going Increases to the left Metallic Character down 04/09/2024 04/09/2024 Practice: Rank the elements from lowest to highest… Electronegativity - C, F, Mg Atomic Radius - Ir, Re, Bi Metallic Character - Rb, Mn, P Ionization Energy - B, Ga, In
