Ionic Bonding Noadswood Science, 2012

Ionic Bonding To understand and be able to represent ionic bonding Thursday, December 07, 2017 To understand and be able to represent ionic bonding

Periodic Table Groups Complete the following statements As you go down group 7 the non-metals… As you go down group 1 the metals… As you go down group 7 the non-metals get less reactive as there is less pull on new electrons to the positive nucleus because there are more shells shielding it As you go down group 1 the metals get more reactive as there is less pull on the electrons in the outer shell because of the shields so they can be easily lost

Reactivity F S Which is less reactive? The sulfur is less reactive than the fluorine – there is less pull on new electrons to the positive nucleus because there are more shells shielding it

Reactivity Li Na Which is more reactive? The sodium is more reactive than the lithium – there is less pull on the electrons in the outer shell because of the shields so they can be easily lost

Ions Ions are electrically charged particles formed when atoms lose or gain electrons This loss or gain leaves a complete highest energy level, so the electronic structure of an ion is the same as that of a noble gas - such as a helium, neon or argon +ve (cation) -ve (anion)

Ions Atoms can obtain completely full outer electron shells by either gaining or losing electrons when they react with other atoms – when this happens, atoms become ions Unlike atoms, ions have an electrical charge because they contain an unequal number of protons and electrons: - Atoms that lose electrons have more protons than electrons and so have a positive charge – they are called positive ions or cations Atoms that gain electrons have more electrons than protons and so have a negative charge – they are called negative ions or anions

Charges I II III IV V VI VII VIII Na Mg Al C N O Cl He 1+ 2+ 3+ * 3- Element example Na Mg Al C N O Cl He Charge 1+ 2+ 3+ * 3- 2- 1- ** Ion symbol Na+ Mg2+ Al3+ N3- O2- Cl- *Carbon and silicon (group IV) usually form covalent bonds (sharing electrons) **Elements within group VIII do not react with other elements to form ions

Metal Ions Lithium – group I (it has one electron in its highest energy level) When this electron is lost, a lithium ion Li+ is formed

Metal Ions Sodium – group I (it has one electron in its highest energy level) When this electron is lost, a sodium ion Na+ is formed

Metal Ions Magnesium – group II (it has two electrons in its highest energy level) When these electrons are lost, a magnesium ion Mg2+ is formed

Metal Ions Calcium – group II (it has two electrons in its highest energy level) When these electrons are lost, a calcium ion Ca2+ is formed

Non-metal Ions Fluorine – group VII (it has seven electrons in its highest energy level) When it gains one electron, a fluoride ion F- is formed

Non-metal Ions Chlorine – group VII (it has seven electrons in its highest energy level) When it gains one electron, a chloride ion Cl- is formed

Non-metal Ions Oxygen – group VI (it has six electrons in its highest energy level) When it gains two electron, an oxide ion O2- is formed

Ionic Bonding When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions – the resulting compound is an ionic compound Consider reactions between metals and non-metals, e.g. sodium + chlorine → sodium chloride magnesium + oxygen → magnesium oxide calcium + chlorine → calcium chloride In each of these reactions, the metal atoms give electrons to the non-metal atoms – the metal atoms become positive ions and the non-metal atoms become negative ions

Ionic Bonding – Demo There is a strong electrostatic force (generated by differences in electric charge) of attraction between these oppositely charged ions, called an ionic bond Many ionic bonds in an ionic compound are arranged in giant lattice structures (a regular grid-like arrangement of atoms)

Building An Ion

Ionic Bonds

Ion Diagrams Dot and cross diagrams are used to show the ions… Draw a dot and cross diagram for sodium chloride… Sodium chloride, NaCl – sodium ions have the formula Na+, while chloride ions have the formula Cl-

Ion Diagrams Draw a dot and cross diagram for magnesium oxide… Magnesium oxide, MgO – magnesium ions have the formula Mg2+, while oxide ions have the formula O2-

Ion Diagrams Draw a dot and cross diagram for calcium chloride… Calcium chloride, CaCl2 – calcium ions have the formula Ca2+, while chloride ions have the formula Cl- Two chloride ions are present, because two chloride ions are needed to balance the charge on a calcium ion

Ionic Formula A formula uses chemical symbols and numbers to show the ratio of atoms of each element present in the compound – to work out the formula of an ionic compound the following needs to take place: - Write down the symbol for each atom Calculate the charge for each ion Balance the number of ions so the positive and negative charges equal zero – this gives a ratio of ions Write down the formula without the ion charges – the metal is always written first

Ionic Formula What is the formula for sodium fluoride?

Ionic Formula What is the formula for aluminium bromide?

Ionic Formula What is the formula for aluminium oxide?

Ionic Compounds Ionic bonds form when a metal reacts with a non-metal – metals form positive ions; non-metals form negative ions Ionic bonds are the electrostatic forces of attraction between oppositely charged ions (+ve and –ve) The oppositely charged ions are arranged in a regular way to form giant ionic lattices (ionic compounds often form crystals as a result)

Lattice In an ionic compound, millions and millions of ions are packed together in a regular cubic arrangement, joined by ionic bonds forming a giant 3D structure called an ionic lattice

Ionic Properties Ionic compounds have the following properties: - High melting and boiling points - ionic bonds are very strong (a lot of energy is needed to break them) causing ionic compounds have high melting and boiling points Conductive when liquid - ions are charged particles, but ionic compounds can only conduct electricity if their ions are free to move so ionic compounds only conduct electricity when dissolved in water or melted

Ionic Properties Ionic compounds do not conduct electricity when they are solid because the ions are packed together and cannot move When molten, however, the lattice breaks up and the ions are free to move (as there are charged particles they can carry an electric current) Ionic compounds are usually soluble in water because water molecules have a slight electrical charge and can attract the ions away from the lattice – when dissolved, the ions are free to move and can carry an electric current

Ionic Properties Ionic compounds are brittle – they shatter when they are hit When the lattice is hit, a layer of ions is shifted so that ions with the same charges are lined up together These like charges repel each other, thereby splitting the lattice

Ionic Properties Ionic Compound Properties Sodium Chloride NaCl High melting point: 800ºC Non-conductive in its solid state, but when dissolved in water or molten NaCl will conduct electricity Magnesium Oxide MgO High melting point: 2,800ºC Mg2+ and O2- ions have a greater number of charges, so they form stronger ionic bonds than the Na+ and Cl- ions in sodium chloride As magnesium oxide stays solid at such high temperatures it remains non-conductive (high-temperature electrical insulation)

Salt Water Conductivity Your task is to design an experiment to test if water / sugar water / salt water is a good conductor of electricity… Explain using a diagram how you would test this Taking a beaker add either the water, sugar water or salt water to it – stir the mixture and connect a circuit up – if the bulb lights the solution is able to conduct…

Salt Water Conductivity Water and sugar water do not conduct, however salt water does – explain why this is the case… Consider what is needed for the flow of electrical current…

Salt Water Conductivity Salt dissociates into ions when it dissolves in water allowing conduction of an electrical current (the large salt crystals separates into smaller ions) This process produces ions which can freely move, transferring electrical charges (and the flow of electrical current) A solution can only conduct an electric current it it contains freely moving ions – water and sugar are both lacking in these

Properties Quiz

Properties Quiz

Anagrams