1.2 IONS UNDERSTANDING HOW THE ELECTRONS MOVE INSIDE AN ATOM ALLOWS SCIENTISTS TO CONTROL HOW ATOMS REACT WITH EACH OTHER.

VOCABULARY PREVIEW  Look up the following terms an provide a definition that you understand.  Anion  Cation  Ion  Ionic bond  Ionic compound  solubility A negatively charged ion A positively charged ion An atom which has either gained or lost an electron An attraction between two oppositely charged ions When anions and cations come together (sodium chloride) How easily something dissolves

USING VISUALS Discuss why lithium is likely to form a cation (positive) when it only has one loose electron around it. Compare this with oxygen or chlorine, which are more likely to gain an electron to complete their shells. Cl

ATOMS AND IONS  Atoms are electrically neutral (what does this mean?)  If an electron is removed or added, the atom becomes charged and is now called an?  When an electron is removed from an atom, that atom becomes a charged ion.  A positive ion is known as a?  If an electron is added to an atom, that atom becomes a charged ion.  A negatively charged ion is known as a? ion They contain an equal number of positive protons and negative electrons. positively cation negatively anion

CATIONS  A cation is formed when an atom loses electrons.  Do you think the outermost shell would be mostly empty or mostly full?  The atom will usually lose all the electrons in the outermost shell so that only filled shells remain.  Almost all cations come from metal atoms, why is this? Page 14- Top Paragraph Mostly empty

COMMON CATIONS  An important non-metallic cation comes from hydrogen (H). Hydrogen ions (H+) are formed whenever an acid is dissolved in water.  The symbols used to represent cations are made up of the atomic symbol and the charge of the ion.  For example: Since sodium (Na) loses one electron, the sodium ion has a charge of +1. This is represented by Na +. Magnesium (Mg) atoms lose two electrons and so the magnesium ion is represented as Mg 2+

ANIONS  An anion is produced when an atom gains electrons. This will occur if the outermost electron shell of the atom is almost full. In that case, the atom gains additional electrons until the shell is filled, as seen below

ANIONS  The name of a cation is the same as the atom, however anions are named differently. The chemical name for an anion is similar to the name of the atom but ends in –ide.  What would the following atoms be called when they become anions?  Chlorine  Oxygen  Nitrogen  Iodine  Fluorine  Sulfur  Bromine Chloride Oxide Nitride Iodide Fluoride Sulfide Bromide

IONIC COMPOUNDS  When anions and cations come together they form compounds made up of large crystal lattices. These compounds are known as ionic compounds.

RECAP What is a  Anion - A negatively charged ion  Cation - A positively charged ion  Ion - An atom which has either gained or lost an electron  Ionic bond - An attraction between two oppositely charged ions  Ionic compound - When anions and cations come together (sodium chloride) What ions are formed whenever an acid is dissolved in water? Hydrogen ions (H+)

CHEMICAL NAMES AND FORMULAS  Naming ionic compounds is very easy  Simply write the name of the cation followed by the name of the anion  Write the chemical name for the following compounds 1. Ca 2+ and O 2- = Calcium Oxide 2. Cu + and Cl - = Copper Chloride

CHEMICAL FORMULAS  Writing chemical formulas is slightly more difficult.  When writing the formula for an ionic compound you must ensure that there is an equal number of positive and negative charges so that the total charge is zero.  Sodium(Na + ) chloride (Cl - ) the chemical formula us just NaCl  Magnesium (Mg 2+ ) chloride (Cl - ) the chemical formula becomes MgCl 2  Charge is at the top, number of atoms is on the bottom.

WRITING IONIC FORMULAS

QUESTION TIME

IONIC BONDING  Cations and anions are attracted to each other because they have opposite electrical charges. When they come close to one another they stick together to form an ionic bond.  Ionic bonds holding crystal lattices together are very strong. Therefore, ionic compounds usually:  Are hard  Are brittle  Have high melting points

IONS IN SOLUTION  Some ionic compounds are soluble(dissolve) in water, while others are insoluble (do not dissolve)

19 NAMES OF SOME COMMON IONS Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

20 CHARGES OF REPRESENTATIVE ELEMENTS Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

21 Complete the names of the following ions. Ba 2+ Al 3+ K + _________ __________ _________ N 3  O 2  F  _________ __________ _________ P 3  S 2  Cl  _________ __________ _________ LEARNING CHECK

22 Ba 2+ Al 3+ K + barium aluminum potassium N 3  O 2  F  nitride oxide fluoride P 3  S 2  Cl  phosphide sulfide chloride SOLUTION

23 Formula IonsName cation anion NaClNa + Cl - sodium chloride K 2 SK + S 2- potassium sulfide MgOMg 2+ O 2- magnesium oxide CaI 2 Ca 2+ I - calcium iodide Al 2 O 3 Al 3+ O 2- aluminum oxide EXAMPLES OF IONIC COMPOUNDS WITH TWO ELEMENTS

24 Write the names of the following compounds. 1) CaO___________ 2) KBr___________ 3) Al 2 O 3 ___________ 4) MgCl 2 ___________ LEARNING CHECK

25 Write the names of the following compounds: 1)CaOcalcium oxide 2)KBrpotassium bromide 3)Al 2 O 3 aluminum oxide 4)MgCl 2 magnesium chloride SOLUTION

26 LEARNING CHECK Write the formulas and names for compounds of the following ions: Br − S 2 − N 3 − Na + Al 3+

27 SOLUTION Br − S 2 − N 3 − Na + Al 3+ NaBr sodium bromide Na 2 S sodium sulfide Na 3 N sodium nitride AlBr 3 aluminum bromide Al 2 S 3 aluminum sulfide AlN aluminum nitride

IONS IN SOLUTION  When ions are in a solution they can move freely through the liquid meaning they can create a flow of electric charge and therefor conduct electricity.  Only liquids that contain ions will allow an electrical current to flow.  Liquids such as oil or kerosene do not contain ions and therefore do not conduct electricity.

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