MEETS Bohr and Lewis Covalent & Ionic

Other Atoms Why Do Ions Form WE ALREADY KNOW ITS TO “FILL” THEIR VALENCE! Atoms will gain or lose electrons in order to fill or empty their valence depending on which is easier. BUT WHERE DO THESE ELECTRONS COME FROM OR GO Other Atoms

Bonding Types: Covalent Bonds: Recall – Non-metals form negative ions This means they “want” to gain electrons to stabilize How can two atoms both gain electrons at the same time? THEY SHARE Covalent Bonds: Formed between two or more non-metals Electrons are shared between atoms

BUT if a Metal were to meet a Non-Metal at the bar ? When two atoms get close together, their valence electrons interact. Ok so what if two metals walk into a bar? Well there would be a bar fight between the metals! Metals “need” to get rid of electrons and there would be no way for them to strike a mutual deal BUT if a Metal were to meet a Non-Metal at the bar ?

It would be love at first sight It would be love at first sight. Well not quite, but they would be able to make each other happy since one “wants” to gain and the other “wants” to lose electrons Ionic Bonds: Formed between metals & non-metals Electrons are transferred between atoms

No but seriously the analogy can help Covalent Molecules – are attached and sharing electrons – this is like marriage. It is a strong connection that is difficult to break.  low reactivity Ionic Compounds – are attracted to each other – this is like dating. The bond is “electric” but if another comes along you might move on. Ionic bonds are not as strong  high reactivity

Pause – Lets Take a Brain Break Complete Part 1 of the Worksheet https://www.wlwv.k12.or.us/cms/lib8/OR01001812/Centricity/Domain/1638/bonding%20practice%20both%20types.pdf

Lewis Diagrams: Like simplified Bohr diagrams Only valence electrons are shown Dots representing electrons are placed around the element symbols (on 4 sides, imagine a box around the symbol) Electron dots are placed singularly, until the fifth electron is reached, then they are paired. Example: Nitrogen atom

Lewis Diagrams: Note: the Lewis diagrams are the same (except for the symbols) for elements in the same family because they have the same number of valence electrons

Lewis Diagrams for Ions: For positive ions: one electron dot is removed from the valence shell for each positive charge of the ion. For negative ions: one electron dot is added to each valence shell for each negative charge of the ion. Square brackets and the charge are placed around each ion Example: Nitrogen ion

Lewis Diagrams For Ionic Bonds: Let’s Try – Sodium and Chlorine Lewis Diagrams For Ionic Bonds: 1) Draw each of their Lewis Diagrams 2) Show the transfer of electrons and then the resulting Ions and their charges

Lewis Diagrams For Ionic Bonds: Now Let’s Try Magnesium and Oxygen Draw each of their Lewis Diagrams The Ionic Compound

Lewis Diagrams For Ionic Bonds: Now Let’s Try Calcium and Chlorine Draw each of their Lewis Diagrams The Ionic Compound ?

Lewis Diagrams For Covalent Bonds: valence electrons are drawn to show sharing of electrons. Remember: All atoms “like” to have a full valence shell The shared pairs (“bonding pairs”) of electrons are usually drawn as a straight line “lone pairs” are the electrons not shared

Extension: IntRAmolecular Forces In the bonds What holds a molecule together IntERmolecular Forces Attraction between one molecule and its neighboring molecules What keeps matter in solid and liquid phases Have you ever wondered why some elements and molecules are solid at room temperature, but others are liquids or gasses?

WHAT IS HAPPENING ATOMICALLY IONIC COVALENT METAL (+) AND NON-METAL (-) Positive and negative ions ATTRACT to one another WEAK intramolecular Forces * Tend to be very reactive Recall the “just dating” analogy – these ions are attracted to each other, but if another ion come a long they are likely to form a bond with it = chemical reaction has occurred Two or more NON-METALS (no ions form) Bond of ATTACHMENT where electrons are shared STRONG intramolecular Forces * Tend to be very unreactive Recall that these are the “married” couple. It take a lot of energy to divorce and meet a new spouse so chemical reactions are less likely

BOHR MODELS IONIC COVALENT Not very useful and not often used Arrows show transfer of ions and then brackets show resulting charged ions that are attracted to each other Useful for determine the shape, arrangement and bod types in the molecules Lone pairs  bonds. For most elements, you are looking to satisfy the OCTET RULE  total of 8 shared electrons per atom Ex. Carbon Dioxide

PROPERTIES IONIC COVALENT BAG OF MAGNETS High Melting and Boiling Points It takes a lot of NRG to separate the molecules from each other STRONG Intermolecular Force BAG OF GOLF BALLS Low Melting and Boiling Points It is easy to separate the molecules WEAK Intermolecular Forces

WHEN DISSOLVED IN WATER* IONIC COVALENT Ions are attracted to the water’s negative and positive poles = DISSOCIATE Ions Separate FYI Pure Water does not conduct Electricity. There are no ions in it to conduct a charge Molecules do not separate, but they spread out from one another = DISSOLVE

WATER IS POLAR WATER IS A COVALENT COMPOUND WATER IS NEUTRAL OVERALL OXYGEN AND HYDROGEN DO NOT SHARE ELECTRONS EVENLY ONE END OF THE WATER IS MORE NEGATIVE THAN THE OTHER

Online Quiz via Classroom before next class!