Presentation on theme: "Bonding in chemicals VELS 6 Earth Metals Transition from metal to non-metals Alkali Group I Alkaline Group II Halogen Gases Group VII Noble Gases Group."— Presentation transcript:
Bonding in chemicals VELS 6
Earth Metals Transition from metal to non-metals Alkali Group I Alkaline Group II Halogen Gases Group VII Noble Gases Group VIII 1 H 1+ 1 2 He 2 3 Li 1+ 2,1 4 Be 2+ 2,2 5 B 2+ 2,3 6 C 4+ 2,4 7 N 3- 2,5 8 O 2- 2,6 9 F 1- 2,7 10 Ne 2,8 11 Na 1+ 2,8,1 12 Mg 2+ 2,8,2 13 Al 2+ 2,8,3 14 Si 4+ 2,8,4 15 P 3- 2,8,5 16 S 2- 2,8,6 17 Cl 1- 2,8,7 18 Ar 2,8,8 19 K 1+ 2,8,8,1 20 Ca 2+ 2,8,8,2
Valence Electrons The Outer Electron shell is the most important shell discussed in chemistry It is called the Valence Electron Shell The Electrons that occupied that shell are called Valence Electrons They are at the highest Energy state
The Most Important Thing The number of valence electrons determines how an atom bonds with other atoms. Valence electrons cause chemical bonding to occur. 1 2 2 3 4 5 6 7 8# of valence electrons So why do elements in the same group have similar chemical properties?
Elements and Compounds Elements are all the different materials in the periodic table they are one type of substance. ◦ If you can find it in the periodic table it is an element! Compounds are made up of more than one type of element. ◦ To make a compound, elements are chemically bonded together.
Element Vs Compounds Aluminium Water Boron Carbon Dioxide Helium
BONDING OPTIONS By transferring electrons (producing ions) (metals-nonmetals) By sharing electrons (nonmetal- nonmetal)
Valence Electrons Electrons in the -outermost energy level or -outermost electron shell or -outermost orbital (involved in chemical reactions) Input Time
IONIC BOND Bond formed between two ions by the transfer of electrons
Ionic Bonds: One Big Greedy Thief Dog!
Very Reactive Metals Earth Metals Transition from metal to non-metals Alkali Group I Alkaline Group II Halogen Gases Group VII Noble Gases Group VIII 1 H 1+ 1 2 He 2 3 Li 1+ 2,1 4 Be 2+ 2,2 5 B 2+ 2,3 6 C 4+ 2,4 7 N 3- 2,5 8 O 2- 2,6 9 F 1- 2,7 10 Ne 2,8 11 Na 1+ 2,8,1 12 Mg 2+ 2,8,2 13 Al 2+ 2,8,3 14 Si 4+ 2,8,4 15 P 3- 2,8,5 16 S 2- 2,8,6 17 Cl 1- 2,8,7 18 Ar 2,8,8 19 K 1+ 2,8,8,1 20 Ca 2+ 2,8,8,2
Forming Ionic Bonds Potassium (K) and Fluorine (F) Magnesium (Mg) and Chlorine (Cl) Sodium (Na) and Oxygen (O) Calcium (Ca) and Sulfur (S) Do you see something in common with these combinations? Hydrogen (H) and Chlorine (Cl) Hydrogen a metal or non-metal? Non-metal at normal temperature and pressure... But becomes theoretically a metal at very high pressures! REMEMBER “non-metals and metals form ionic bonds” Also Hydrogen is special as it can form ionic bonds with non- metals and metals as well even though it is a non-metal normally!
Exceptions to the Octet Rule Hydrogen (H) only has one electron on the outer shell, thus requires another one to form bonds so that it has 2 valence electrons.
IONIC BOND Substance formed when electrons are transferred between 2 or more substances making ions. Happens between Metals and Non-metals The ions have an electrostatic attraction with each other to form an Ionic Bond. Input Time
Octet Rule Atoms want 8 (or 0) valence electrons Wants to be a noble gas!! As in…wants to have a complete valence shell
Lets try to draw some covalent bonds! Potassium (K) and Chloride (Cl) Valency of K and Cl? Octet Rule Applied! Don’t Forget to write the formula too!!
Lets try to draw some ionic bonds! Magnesium (Mg) and Chlorine (Cl) Valency of Mg and Cl? Octet Rule Applied! Don’t Forget to write the formula too!! Input Time
COVALENT BOND Bond formed by the sharing of electrons between (non metal - nonmetal)
Two fluoride atoms share one electron each to forms a covalent bond. Covalent bonds also follow the Octet Rule (8 valence electrons each) (except for very special cases like hydrogen 2 valence electrons) Molecules are neutral groups of atoms held together by covalent bonds!
What are these two elements? Are they metal or non-metals? What type of bond would they form? Remember Hydrogen is special When bonding don’t worry about the inner electrons!!! New count the valence electrons! Make sure there is 8 or two for hydrogen Uh-oh not enough!!! Find another atom to complete the share! THIS IS A WATER MOLECULE!!!!! Covalent Bonds: Hydrogen Shares electron with oxygen and vice versa!
Sharing one pair creates Single Bonds Sharing four electrons creates Double Bonds Sharing one pair and a second separate pair Sharing four separate pairs Input Time
Summary of The Octet Rule REMEMBER! ◦ All elements want to be like noble gases ◦ Thus they want full electron shells. ◦ Full electron shell are 8 valence electrons. The Octet Rule ◦ Atoms form chemical bonds so that they have an octet of valence electrons. Either by Gaining, losing valence electrons or Sharing valence electrons. ◦ In other words: When atoms bond together, they each want a set of 8 valence electrons. (except for hydrogen who wants two) Input Time
DRAWING MOLECULAR STRUCTURES Electron Dot Diagram Lewis Dot Diagram Structural Formula
Electron Dot Diagrams Electron dot notation is a way of showing how many valence electrons an element has. LiBeBC NOFNe HHe
Lewis and Structural Lewis structures ◦ Lone pairs are unshared electrons, which are not involved in chemical bonding. (Dotted Pairs) ◦ Shared electrons are involved in chemical bonding. (Line) Structural formulas do not show dots for lone pairs of electrons. FF FF Input Time
How to Draw the Bonds FF Step 1: Figure out how many more valence electrons each atom needs to make an octet (F needs 1). Step 2: Make sure all elements in the molecule can have an octet. FF Step 3: Draw the Lewis structure. FF Step 4: Write the structural formula. FF
Hydrogen Fluoride (HF) Hydrogen Gas (H) 2 HFHF HF HH HH HH Lewis Structure Structural Formula Make sure all atoms have octets (H only wants 2 valence electrons). HFHH
Methane (CH 4 ) HC H H H H C H H H H CH H H
Nitrogen Trifluoride (NF 3 ) Draw the Lewis Diagram and Structural Formula Input Time
Nitrogen Trifluoride (NF 3 ) Draw the Lewis Diagram and Structural Formula N F FF N F FF NFF F N F FF
Will these molecules form??? CFF NH Input Time
Naming Compounds Number of atomsPrefix 1mono- (use only for oxygen) 2di- 3tri- 4tetra- 5penta- 6hexa- 7hepta- 8octa- Examples P 2 O 5 - this is named diphosphorus pentoxide, because there are two phosphorus atoms and five oxygen atoms. CO - this is carbon monoxide (you need the "mono-" because there's only one oxygen atom). CF 4 - this is carbon tetrafluoride, because there's one carbon atom and four fluorine atoms. Input Time
WHICH IS BOND STRONGER? Ionic bonds are a bit stronger than Covalent bonds but both are strong bonds
Strength of ionic compounds In an ionic compound the ionic bonds are spread evenly through the whole substance as a network so they are generally very strong with high melting points. They tend to made solids compounds Input Time
Strength of covalent molecules In a covalent molecule each molecule has strong covalent bonds inside it. It has weaker attractions between the molecule. Often simple molecular chemicals are gases and liquids. Though the intermolecular bonds are weak the molecular bonds are strong Input Time
Quiz 1.Draw the electron dot notation for Calcium (atomic number = 20). 2. Draw the Lewis structure for a molecule with 1 hydrogen atom and 1 chlorine atom, HCl (atomic numbers = 1, 17). 3. Book Exercises - Section 2.2 over to you questions, All of it!!!