!! Unit*2.*Atomic*Theory*! Molar!mass!calculation!using!the!abundance!of!isotopes!of!an!element!!!! Electron!configuration!(both!full!notation!and!core!notation)!(HI!#12)! o Neutral!atom,!anion,!cation!(ensure!you!know!the!rules!associated!with!ions)! o What!does!isoelectronic!mean?!!! Periodic!Table!! o Four!Trends!(Atomic!Radii,!Metallic!Character,!Ionization!Energy,!and!Electronegativity)! # How!do!they!behave!as!you!go!down!(or!across)!the!periodic!table?!Explain!Why.!!! Chemical!Bond! o Ionic!and!covalent!bond!(M!+!NM!or!NM!+!NM)!(Complete!transfer!of!e S!or!sharing!of!e S )! o Electronegativity!difference!values!used!to!determine!the!type!of!bond!(Ionic!bond,!polar! covalent!bond,!nonspolar!covalent!bond)! o London!force!(Why!does!it!occur?!What!situation!causes!strong!London!force?)!!! Lewis!Diagram!(HI!#13)! o Ionic!compound!(Do!not!forget!to!write!square!brackets!and!charges!around!ions)! o Covalent!compound!(Review!the!step!by!step!method)!!!!
Chemistry 11 Early models of the atom 1 Structure of the Atom Democritus Developed the idea of Thought things were made of atoms that have different Aristotle Matter is made of different amounts of:,,, and John Dalton Elements are made up of very atoms. An element is made up of a group of atoms. A particular combination of specific types of atoms creates. Chemical reactions involve the re-shuffling of the atoms in a compound to make new compounds. JJ Thomson Atoms contain.. Model (Draw in the box)
Chemistry 11 Early models of the atom 2 Earnest Rutherford experiment. Most of the alpha particles (positively charged).! Atom is mostly with a positively charged.! Nucleus contains almost all the mass of the atom and consists of and.! The number of electrons surrounding the nucleus equals the number of protons in the nucleus, but electrons are much lighter than protons. Niels Bohr Electrons had rather than being randomly distributed. Quantum Model (Erwin Schrodinger), but they move around the nucleus in a random, but slightly predictable way.
Chemistry 11 Atomic Theory Study Guide 1 Subatomic Particles: Electrons, Protons, and Neutrons Rutherford-Bohr Model: Definitions: Proton: Neutron: Electron: Symbol Charge Mass (amu) Electron Proton Neutron Atomic Number and Mass Number Look at K for example: 19 K Potassium 39.098 Definition: Atomic Number: Of an element is the of its atoms. No two elements have the atomic number. This number defines an. Increases by as you go through the periodic table (refer to periodic table) Number of protons = (in neutral atoms) Therefore, for K: 19 protons = electrons in a neutral atom.
Chemistry 11 Atomic Theory Study Guide 2 So how do we fill the electrons in the shells? We follow the rule that certain shells can hold a certain number of electrons. 1 st shell: e - 2 nd shell: e - 3 rd shell: e - 4 th shell: e - etc. We will only focus on the first 20 elements for now! Bohr Diagram for K: Ions: Electrons can be from an atom if enough is applied to it. For example, Na atom Na + sodium atom remove e - sodium ion 11 protons 11 protons 11 electrons 10 electrons Ions usually form as a result of atoms having. +ve charged ions have electrons, while ve charged ions have electrons Bohr Diagram for Na + : How do we find out the number of neutrons in an atom? Definition: Mass number:..
Chemistry 11 Atomic Theory Study Guide 3 By convention, number 39 number 19K Example using K: How many neutrons are present in an atom of K that has mass number = 39? mass number = number of protons + number of neutrons number of neutrons = = = Isotopes Not all atoms of the same element contain the same number of (remember number of protons determines the identity of elements, NOT the number of neutrons). Definition: Isotopes: Example: Carbon, C has three naturally occurring isotopes: C-12, C-13, C-14 Electron Configuration Definition: Electron Configuration: 4 types of shells: s orbitals can hold e - p orbitals can hold e - d orbitals can hold e - f orbitals can hold e -
! Isotope Calculation Chemistry 11 Isotope Calculation Study Guide Complete the following table: # of p +!"!"!"!! or C-12!! or C-13!! or C-14 # of e - # of n Atomic # (# of p + ) Mass # (# p + + n) Atomic mass Why is the mass number of element different from the atomic mass? The mass number is a whole number which represents sum of # of p+ and n but atomic mass is usually a decimal number which represents the molar mass of the element. Definition: Molar mass: e.g., Molar mass of Cl is. Where did this number come from? Scientific data tells us that there are two isotopes of chlorine Cl-35 and Cl-37. 75.77% of the element is Cl-35 and 24.23% of it is Cl-37.!"#$%!!!"##! =!!"#$%&'(!!"!!"#$#%&!!!(!"##!#!) e.g., What is the molar mass of boron, given that there are: 18.8% of B-10 Rest is all B-11 e.g., What is the molar mass of magnesium, given that there are: 78.99% of Mg-24 10.00% of Mg-25 Rest is all Mg-26!!
Chemistry 11 Atomic Theory Study Guide Electron Configurations for Neutral Atoms: Since we can t use the Bohr diagram to accurately describe the electrons in an atom, we need a new way to describe them. This is known as the electron configuration! Electron configuration: Shell number : Orbital: : There are 4 types of orbitals: s orbitals can hold e - p orbitals can hold e - d orbitals can hold e - f orbitals can hold e - Shell number What orbitals are available 1 2 3 4 E.g., He has 2 electrons! Be has 4 electrons! Ne has 10 electrons! Ar has 18 electrons! Zn has 30 electrons! Orbitals with the lower energy are filled before ones with higher energy. Remember the diagram to guide you figure out the order. (This WILL NOT be given to you on test/quiz.)
Chemistry 11 Atomic Theory Study Guide As you go further down the periodic table, you can see how much longer the configurations are! Your hands will suffer from tremendous stress and pain!!! Thus we need a shortcut notation called the Core Notation. Core Notation: E.g., Al has 13 electrons! Ti has 22 electrons! Ca has 20 electrons! How to write electron configurations for ions: For negative ion AKA 1. Write the electron configuration for the neutral atom first. Then add the extra electrons into the appropriate orbital. E.g., O 2-! Cl -! S 2-! For positive ion AKA 1. Write the electron configuration for the neutral atom first. Then remove electrons from the shell with the highest. 2. If there are multiple shells with the highest, then remove from orbital, then orbital then orbital. E.g., Al 3+! Cu 2+! Sn 2+!
Chemistry 11 Atomic Theory Study Guide How to predict the number of valence electrons using electron configurations: To find out which electrons actually take part in a chemical reaction (the valence electrons), we only look at the electrons that are:! AND! E.g., Aluminum atom!! has valence electrons. 2 electrons in the orbital, and 1 electron in the orbital. Gallium atom!! has valence electrons. The electrons in the orbital are NOT valence electrons. Isoelectronic: E.g., Which of the following are isoelectronic? (Write the electron configurations first.) He! F -! Be 2+! S 2-! Na +! P 3-! Mg 2+!
Chemistry 11 Atomic Theory Study Guide The Periodic Table and Its Trends The modern periodic table, which was designed by Mendeleev, contains all the elements that have been discovered. It organizes elements according to. Classifying elements according to their metallic character: There is a that separates the metals from non-metals On the left are the and on the right are the are elements that are found next to the zig-zag line and have properties of both metal and non-metal. (e.g., B, Si, Ge, As, Se, Sb, Te) Arrangement of elements on the periodic table: Definition: Period: Group (Family) : Some special groups of elements: Alkali Metals (Group 1) Have e- in the outermost shell and have ions Very (especially with water) Reactivity increases as you go of the family o This is generally true for all families More notes about other families on Family Ties worksheet. Other trends: Atomic Radii, Metallic Character, Ionization Energy, Electronegativity Definition: Atomic radius: As you go from to, the size of atom so atomic radii. As you go from to, atomic radii because of increase in between protons and electrons. (More protons can electrons tightly.)
Chemistry 11 Atomic Theory Study Guide Metallic character: OR : As you go from to, the metallic character. As you go from to, the metallic character. Why? Ionization Energy: OR : As you go from to, the ionization energy. As you go from to, the IE. Why? Electronegativity: OR : As you go from to, the electronegativity. As you go from to, the EN. Why? Summary:
Chemistry 11 Atomic Theory Study Guide Electron Configuration Introduction Inquiry Activity Column Element # e - Row Block within the Electron configuration block Li 3 1s 2 2s 1 Be 4 1s 2 2s 2 N 7 1s 2 2s 2 2p 3 F 9 1s 2 2s 2 2p 5 P 15 1s 2 2s 2 2p 6 3s 2 3p 3 Mn 25 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 Br 35 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 Y 39 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 1 Questions: 1. How is the # of e - for an element related to the number found in its electron configuration? 2. How is the location of the element (row) related to the number found in its electron configuration? 3. How is the location of the element (block) related to the number found in its electron configuration? 4. How is the location of the element (column) related to the letter found in its electron configuration? 5. The numbers in front of letters represent. 6. The letters represent. 7. The superscripts represent.
Chemistry 11 Isotope Calculation Study Guide Column Element # e - Row Block within the Electron configuration block Be 4 2 s 2 N 7 2 p 3 F 9 2 p 5 Mn 25 4 d 5 Y 39 5 d 1 Cr 24 4 d 4 Cu 29 4 d 9
Chemistry 11 Chemical Bonding Notes Why do chemical bonds form? Back in atomic theory, we remember that all atoms would like to have a full and complete of electrons. To do so, an atom would have to either their electrons away to another atom, or electrons from another atom. Thus, a relationship, or a has to form between atoms. What determines whether an atom gives or takes electrons? Earlier in the year, we also discussed about the concept of, where an atom has a certain degree of for electrons. If an atom has a electronegativity, it attracts electrons from another atom. Thus, it will tend to electrons away from another atom to their outer shell. These atoms are usually the. If an atom has a electronegativity, it to attract electrons from other atoms, nor like its electrons either. It would rather them away to another atom to obtain a full (inner) shell. These atoms are usually the. What kind of bonds can be formed between atoms? When a atom and a atom get together, an bond is formed between them. Electrons from the metal atom are to the non-metal atom, which creates a metal ion and a non-metal ion. The of these charges together forms the ionic bond. Ionic bond: If we draw a showing only the outer electrons for each atom, the following would represent an ionic bond between two atoms: Li + F Li + F F takes valence e from Li Ionic bonds are really, so compounds that are held together by ionic bonds have melting temperatures because they require a lot of energy to break those bonds. For example, LiF has a melting temperature of C.
What happens if two atoms both have high electronegativities? When two atoms get together, they both have tendencies to attract electrons from each other. Since both are not willing to part with their electrons, they decide to them in a bond. Covalent bond: Example: F + F F F Each F atom will share Each F can now say it has one e with each other 8 e at any given time. Covalent bonds tend to be quite, with some compounds having (eg. O2) and even (eg. N2) covalent bonds between their atoms. How do you predict the formula of covalent compounds? To predict the formula of a covalent compound made from two elements, we use the (or the ) of each element. Combining Capacity: The following are the combining capacities for the elements in each group or column on the periodic table: Group 1 2 13 14 15 16 17 18 Combining Capacity Two steps in predicting the formula: 1. Write the combining capacities above each element in the formula. 2. Crossover the combining capacities so they become subscripts in the formula Example: Predict the formula of the compound formed from P and O. P is in Group Combining capacity is O is in Group Combining capacity is P O
Is there another way to determine what type of bond two atoms will form with each other? An American scientist named devised a method of calculating the electronegativities of atoms in chemical bonds. He assigned each element an as shown on the table below: The between the electronegativities of two atoms in a bond can be used as a guide to determine if an ionic or covalent bond is formed. If the difference is: Greater than 1.7, an is formed between the two atoms Less than 0.2, a is formed (bonding e shared ) Between 0.3 and 1.6, a is formed (bonding e shared ) Example: Classify the bond that is formed in NaF. Na has an value of and F has a value of Difference is (Therefore, is formed!) Try to classify the bond formed in each of these compounds: HBr, Cl2 and MgI2
Are there any forces interacting between two molecules? So far we talked about the bond between two atoms within a molecule. These bonds are usually strong and are known as forces. There are also that act between two molecules that are close to each other. They are responsible for the molecules together especially in the and phases. These forces are called. One type of van der Waals force is called the. London Force: When two molecules are close together, the electrons on one molecule are by the electrons on another molecule (like repels like). Thus, the electrons to a different region on the molecule. This exposes the charged nucleus which the electrons are attracted to. The formation of a temporary and end of a molecule is known as a. London forces result when the dipoles of two molecules are to one another. e e +2 +2 δ δ + δ δ + e e e distribution in He atoms temporarily A temporary dipole is created more to one side in atom than the other London forces are present, but are the type of bonding force known when compared to ionic and covalent bonds. London forces are important between two atoms, and two molecules. [Eg. He (l), CH4 (l), H2 (l)] Also, the electrons an atom or molecule has altogether (greater the ), the the London forces will be! H H H H
Summary of bonds Atomic Theory Unit Chemistry 11 Occur between what? Intermolecular? Intramolecular? Strength (Weak or Strong) ΔEN Ionic bond Covalent bond London force Greater than = Polar covalent Less than = Non-polar covalent N/A Electrons are (Migrated within atoms, transferred or shared) Shared Shared Note Follow octet rule when drawing a Lewis diagram The more electrons there are, the stronger the London force NaCl, KBr ICl, H 2 O Cl 2, CS 2 Between 2 hydrogen molecules Example:
Chemistry 11 Lewis Structures Study Guide After discussing about ionic and covalent bonds, there are times when it is valuable to draw ( electron dot diagrams ) to visualize how electrons are distributed in an atom, ion or molecule. These structures will also allow us to determine the of certain molecules in solution which we will learn later in the course! Lewis Structures of Simple Ionic Compounds To draw the Lewis Structure for ionic compounds: 1. Determine the charge expected for each atom in the compound. 2. Arrange the nonmetal atoms symmetrically around the metal atom. 3. Fill in the valence electrons for each atom. 4. Remove the electrons from the outer shell of the metal atom to form the ion. 5. Distribute the electrons equally to each nonmetal atom to form the ion. Example: Draw the Lewis Structure of MgCl2 Mg has valence e ; will form ion. Cl has valence e ; will form ion. Cl Mg Cl Lewis Structures of Covalent Compounds that Obey the Octet Rule The octet rule states that most atoms (except hydrogen) tend to have electrons in its outer shell as a result of forming covalent bonds. To draw the Lewis Structure for covalent compounds: 1. Count up the total number of valence electrons for each atom in the molecule. 2. Adjust the total number by one electron for every positive charge, and one electron for every negative charge on the molecule (if applicable). 3. Determine which atoms are bonded together and show this bond by drawing a line connecting the two atoms. This bond reflects electrons. 4. Subtract the number of bonding electrons from the total number of valence electrons. 5. Place the remaining valence electrons on the atoms first to complete the octet. 6. Place all left over electrons around the atom if necessary. 7. If a central atom has less than an octet of electrons, have a neighbour share electrons with the deficient atom by putting of electrons into the bond (ie. Double and Triple bonds)
Example: Draw the Lewis Structure for CH4. (C is the central atom!) C has valence e. Each H has valence e. H Central Atom H C H 8 total e 8 bonding e = 0 e left! H Terminal Atom Example: Draw the Lewis Structure for NO2. (N is the central atom!) N has valence e. 5 e Each O has valence e. 12 e Add e for negative charge. 1 e 18 e total O N O 18 total e 4 bonding e = 14 e left! Place remaining e around O first. Then place left over e around N. [ O N O ] Notice that N only has 6 e around it. Have one of the O donate an extra pair of e to the bond to form a double bond! [ O N == O ] [ O == N O ] Depending on the oxygen you chose to donate an extra pair, you would have drawn a different structure. These interchangeable structures are known as structures. Exceptions to the Octet Rule Certain atoms a full octet of electrons after covalent bonding. can only have electrons in its outer shell. Other atoms such as (4 electrons), and (6 electrons) can only share a certain number of electrons due to the fact that they have. They are unable to pull extra electrons on a nearby atom into the covalent bonds.
A molecule in which one or more atoms (except hydrogen) don t possess a full octet of electrons is called an molecule. Example: Draw the Lewis Structure for BF3. (B is the central atom!) B has valence e. 3 e Each F has valence e. 21 e 24 e total F B F Note that B only has 6 e around it. No attempt is made to donate extra electron pairs to the bonds. F Some elements in the and of the periodic table may have valence e in the outer shell after covalent bonding. This is due to the fact that the extra electrons can fit in the of these atoms. Atoms that are able to have more than 8 electrons have an. Example: Draw the Lewis Structure for PCl5. (P is the central atom!) P has valence e. 5 e Each Cl has valence e. 35 e 40 e total Cl Cl \ / Cl P Cl Note that P has 10 e around it. No attempt is made to alter this arrangement. Cl
Date: Block: Name: Chemistry 11 Lewis Structures Funsheet Answer all questions on a separate sheet of paper showing all your work. Attach your answers to this sheet and hand it in at the end of class. 1. Give the Lewis Structure for the following atoms and ions: a) He f) Be b) Si g) Ga c) Al 3+ h) N 3 d) P 3+ i) O 2 e) Ca 2+ j) S 2 2. Give the Lewis Structure for the following covalent compounds: a) HCl k) I2 b) HCHO l) C2H6 O H H H C H H C C H H H c) BeF2 (F Be F) m) SCl2 (Cl S Cl) d) O2 n) NH2 (H N H) e) N2 o) ICl f) HPO2 (H O P O) p) SiO2 (O Si O) g) S2Cl2 (Cl S S Cl) q) CNO h) CH2CCCH2 r) SO4 2 H H O C C C C O S O H H O i) C4H4 s) NO3 H C C H O N O H C C H O j) HCN t) H2O (H O H)
Date: Block: Name: 3. Give the Lewis Structure for the following ionic compounds: a) KI d) MgBr2 (Br Mg Br) b) AlCl3 e) K3P Cl Al Cl K P K Cl K c) MgO f) Na2S (Na S Na)