Presentation on theme: "Identify the elements present in each of the following compounds and the number of each element atom present. Common salt: NaCl Nitric acid: HNO 3 Carbon."— Presentation transcript:
Identify the elements present in each of the following compounds and the number of each element atom present. Common salt: NaCl Nitric acid: HNO 3 Carbon dioxide: CO 2 Sodium Hydroxide: NaOH Sodium carbonate: Na 2 CO 3 Copper sulfate: CuSO 4 Sodium bicarbonate: NaHCO 3 Ammonium sulfate: (NH 4 ) 2 SO 4 Potassium permanganate: KMnO 4 Sodium thiosulfate: Na 2 S 2 O 3 Calcium bicarbonate: Ca(HCO 3 ) 2 Calcium Nitrate: Ca(NO 3 ) 2
Properties of Ionic Compounds They have high melting and boiling points They are hard and brittle They do not conduct electricity in the solid state Will conduct electricity when in solution (dissolved in water) or molten (liquid state) Will often dissolve in water to form ions
Ions – Charged atoms or molecules An ion is an atom or molecule which has lost or gained one or more electrons, making it positively or negatively charged. Anions are negatively charged ions because they have more electrons in its electron shells than it has protons in its nuclei. They gain electrons e.g. Cl atom Cl - Cations are positively charged ions because they have more protons than electrons. Cations lose electrons e.g. sodium Na + The number of electrons an atom gains or loses is called its valency Cations and anions only form when cations transfer their outershell electrons to the anions
Getting stable – Bonding The noble gases have a full outer shell and are very unreactive or stable Atoms are most stable when their outer shell is full like the noble gases How do you get a full outer shell? gain or lose or share electrons when forming compounds and molecules A covalent bond is formed when electrons are shared between atoms. An ionic bond is formed when electrons are transferred from one atom to the other
Ionic Bonding Where does the Chlorine ion get that extra electron from? From Sodium who wants to give one away! In ionic bonding, electrons are completely transferred from one atom to another. It happens between a metal and a non metal Why? Because metals form positive ions (cations) and non metals form negative ions (anions) The oppositely charged ions are attracted to each other by electrostatic forces
During a reaction of sodium with chlorine, sodium loses its one valence electron to chlorine.
Resulting in a positively charged sodium ion and negatively charged chlorine ion.
Some important things to know Where do you find the charges for ions? Look at your valency table? Subscript is set below a word Hello Yr 11 Superscript is set above the Hello Yr 11
Rules for writing chemical formulas 1.Write the symbols and charge for ions involved. Write charge as superscript. 2.Determine the subscripts that will produce no charge 3.Check that the total positive charge and negative charge equal 0 4.Write final chemical formula without the charges just subscripts Mg 2+ Cl - Mg 2+ 2Cl - 2+ 2- = 0 MgCl 2
Polyatomic Ions For polyatomic ions you cannot change the formula of the ion. For polyatomic ions if there is more than one of them you must put them in brackets and place the subscript outside Na + SO 4 2- Al 3+ SO 4 2- 2 Na + SO 4 2- 2 Al 3+ 3SO 4 2- 2+ 2- =0 6+ 6- = 0 Na 2 SO 4 Al 2 (SO 4 ) 3
Fill in the table Iodide I - Oxide O 2- Copper Cu 2+ Potassium K + Aluminium Al 3+
Form an ionic bond between the following Na and Cl Cl and F Na and Mg Mg and Br NH 4 + OH - NH 4 + SO 4 2-
Naming Ionic Compounds 1. Name the positive ion first by writing full name of metal For metals that can have more than one charge (valency) the name of the metal is followed by the valency in capital Roman numerals in brackets e.g. Iron(II) Chloride 2. Name the anion second. Negatively charged elements have the suffix or ending -ide Examples are oxide (O 2- ), sulfide (S 2- ), fluoride (F - ), chloride (Cl - ), bromide (Br - ), iodide (I - ), nitride (N 3- ), hydride (H - )
Naming Ionic Compounds 3. Polyatomic ions which include oxygen in the anion have the suffixes -ate or -ite. "ate" means there is more oxygen in the anion than one ending in "ite" Examples: sulfate (SO 4 2- ) has more oxygen than sulfite (SO 3 2- ), nitrate (NO 3 - ) has more oxygen in the anion than nitrite (NO 2 - ) Other examples are carbonate (CO 3 2- ), phosphate (PO 4 3- ) and permanganate (MnO 4 - ) Exception: OH - is named hydroxide
Fill in the names of the following compounds Iodide I-Oxide O 2- Copper Cu 2+ Copper (II) Iodide Potassium K + Aluminium Al 3+
The ionic bonding model Positive metal ions (cations) and negative non metal ions (anions) are arranged in a regular arrangement, called a lattice The 3D lattice is held together strongly by electrostatic forces Electrostatic forces are the forces between particles that are caused by their electric charges
Explaining properties of ionic compounds Why do ionic compounds have relatively high melting points? Remember the melting point of a compound is when it goes from being a solid to a liquid The bond between the cations and anions are very strong and hence a large amount of energy is required to separate the bonds.
Why are ionic compounds brittle? When an external force distorts the crystal this causes ions of like charge (e.g. ++) to come close together (align) and the repulsion between these ions shatters the crystal. Why are ionic compounds hard? The bonds between the cations and anions are very strong.
Why do ionic compounds conduct electricity when in solution or molten? When molten (liquid) ions are able to slide past each other. While in solution (meaning in water) ions dissociate (move out) from the lattice and can move freely so are able to conduct electricity Why do ionic compounds not conduct electricity when solid? When solid, the ions are not able to move.
Why do ionic compounds dissolve in water? Water molecules are able to move between ions and free them by disrupting the rigid crystal structure
Uses of Ionic compounds Read the pages 103 – 104 and summarize Yr 11 Camp Homework Due Date: Wednesday Week 3 Complete Ionic compound sheets. Add words to the glossary at the back of your workbook (look at pg 51, 70, 90 and 107 of your Chemistry textbook at key terms). Read Chapter 7: Covalent molecules, networks and layers (pages 110 – 131).