Topic 2 - Bonding, Structure and the Properties of Mattter

• What are ions? Charged particles formed when electrons are lost or gained by an atom or molecule
• What type of ions do metals form and how? Metal atoms lose electrons and form positive ions
• What type of ions do non-metals form and how? non-metals gain electrons and become negative ions
• What is the electronic structure of an ion? A full outer shell, like a noble gas
• When does ionic bonding take place? Between oppositely charged ions
• Give an example of when ionic bonds might be formed? When a metal and a non-metal react the metal loses electrons and the non-metal gains them. They form a positive and negative ions and become ionically bonded
• What are ionic bonds? Ionic bonds are the strong electrostatic forces of attraction that hold oppositely charged ions together in an ionic compound
• How do you draw a dot and cross diagram for ionic bonding? Work out what elements are involved e.g. if the question asks to draw the dot an cross diagram for calcium chloride you know calcium and chlorine are the elements involvedFind out what ions each of the elements formed make by looking at their group on the periodic table e.g calcium forms Ca2+ and chlorine forms Cl- Balance it to find out how many of each element is involved. In the examples above two chlorine are needed to balance the 2+ charge of the calciumDraw out the ionic electronic configurations for the elements after they have gained/lost electrons. use dots for one type of element and crosses for the other.If you used dots for the metal's electrons then use dots to represent the electrons it gave to the non metal(s) tooDraw big sqaure brackets around all of the ions and write their charge at the top right
• What is an ionic compound? A giant structure of ions, held together in a lattic by strong electrostatic forces between the oppositely charged ions known as ionic bonds
• Give three ways used to represent ionic compounds Dot and cross diagrams3D ModelsBall and stick models
• Give an advantage of a dot and cross diagram It shows what the ionic compound is formed from
• Give three limitations of a dot and cross diagram Doesnt show the structure of the compounddoesnt show the relative sizes of the ionsdoesnt show how the ions are arranged
• Give 2 advantages of 3D models in showing the structure of ionic compounds show the relative sizes of ionsshow the regular pattern of an ionic compound
• Give a limitation of a 3D model in showing the structure of an ionic compound They only show the outer layer of the compound
• Give three advantages of a ball and stick model in displaying the structure of an ionic compound They show the regular pattern of an ionic compoundThey often suggest that the compound extends beyond the diagaramSometimes shows the relative sizes of the ions
• Give two limitations of a ball and stick model in displaying the structure of an ionic compound They sometimes do not show the relative sizes of the ionsthey suggest there are gaps between the ions when in reality there is not
• What is an empirical formula? The simplest whole number ratio of atoms in a compound. For example, MgCl2 is an empiracal formula showing that in the compound there is twice as many chloride ions as magnesium ions
• How do you find the empirical fomula from a dot and cross diagram? Count how many atoms there are of each element
• What is the empirical formula: CaCl2
• How do you work out the empirical formula from a 3D model or a ball and stick model? Look at the diagram to see which ions are present in the compoundBalance the charges to work out exactly how many of each are in the compound
• What is the empirical formula of the following compound: Balance the charges of potassium and oxygen to get K2O
• Do Ionic compounds have high or low boiling points? Ionic compunds have high boiling points
• Do Ionic compounds have high or low melting points? High
• Why do ionic compounds have high melting and boiling points? The strong electrostatic forces of attraction between the ions require lots of energy to overcome
• Are ionic compounds soluble? ionic compounds dissolve in water
• Do ionic compounds conduct electricity? Not when solid. They conduct electricity when melted or dissolved
• Why do ionic compounds not conduct electricity when solid? When they are soild the ions are held in fixed positions and cannot move to carry electrical charge
• Why can ionic compounds conduct electricity when melted or dissolved? When they are melted or dissolved the ions can move freely and carry electrical charge
• When is a covalent bond formed? A covalent bond is formed when a pair of electrons is shared between two atoms
• What is a covalent bond? A covalent bond is a strong electrostatic force between the positive neclei of the atoms and the pair of electons they share
• Covalent bonds form between a non-metal and another non- metal
• Give three ways covalent bonding can be represented dot and cross diagramsdisplayed formulas3Dmodels and ball and stick diagrams
• 1 Displayed formula
• Give a disadvantage of using 3d models or ball and stick diagrams for showing covalent bonds They can quickly get confusing for large molecules
• Give a disadvantage for displayed formulas They dont show the 3d structure of the molecule
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• What are simple molecules? A few atoms joined by covalent bonds
• Dot and cross diagram for H2
• Dot and cross diagram for Cl2
• displayed formula for H2