g'day great nines i'm miss babo and welcome to the physical sciences part of natural sciences today's lesson we will be doing a bit of revision and learning about compounds in this section we are going to do revision on the periodic table that was completed in grade 8 and we are going to teach you about compounds making compounds and naming compounds let's start with the periodic table firstly what is the periodic table it is a table of chemical elements that are arranged with elements with similar atomic structures and characteristics that are grouped together in the periodic table there are rows which are horizontal and columns which are vertical each block found on the periodic table can give you the following information in each tile or each block there will be the chemical symbol representing the element the atomic number which shows us the number of electrons and protons and we have the mass number how we use the periodic table each block or tile will give us symbol on top of the symbol is the atomic number now the atomic number will always be the same number of protons as they are electrons the reason for this is because on the periodic table it shows us the atomic information of a neutral atom neutral meaning there will be the same number of positive charges which are protons as the negative charges which are electrons the mass number will always be the slightly larger number on the periodic table the mass number will show us the amount of neutrons if we have the mass number minus the atomic number remember in an atomic structure the electrons orbits around the nucleus and within the nucleus the protons and the neutrons can be found now there is quite a bit of information we are able to obtain from the periodic table let's start with the groups they are the vertical columns on the periodic table all the elements in the same group have the same number of electrons in the outermost energy level those are called valence electrons elements of the same group will have similar physical and chemical properties but there are four groups that have specific names which you must remember group one on the periodic table is the alkali metals which is this group over here group two is known as the alkali earth metals which is next to group one then on the other side of the periodic table we have group seven which is this group over here and they are known as halogens and group eight which is the last group over here are known as noble gases with regards to periods periods are the horizontal rows of the periodic table all the elements in the same period have the same number of energy levels for the electrons if you have a look at this diagram over here this inner red circle is the nucleus and all the circles surrounding them are our energy levels with the electrons in that are orbiting around the nucleus so to sum it all up here on our periodic table the black arrows represent the periods and the blue arrows represent the groups starting with alkaline metals alkali earth metals halogens and noble gases with regards to metals and non-metals if we were to have a look at our periodic table to the left of the periodic table and below it represents the metals in this periodic table given to you the metals are represented in red to the right and above on the periodic table will be non-metals and they are represented in a bluish purple color and between the metals and non-metals will be our metalloids or another name for them will be semi-metals now when we look at properties of certain elements we separate them into metals non-metals and semi-metals metals are all solid except for mercury they are shiny in color they are ductile which means they are able to be drawn into thin wires they are malleable which means they can be hammered or manipulated into flat sheets all metals are good conductors of heat and electricity they give off electrons when during a reaction and they have a high melting point now with non-metals they are can be considered solid liquids or gases they are considered to be brittle which means they can break easily they are dull in color they are not ductile which means they cannot be drawn into thin wires they are not malleable which means they cannot be hammered into flat sheets they tend to be poor conductors of heat and electricity they tend to gain electrons during reactions and they have low melting points now are semi-metals or metalloids are all solids they can conduct electricity only when there is an increase in temperature they can be ductile as well as malleable and they tend to give electrons off during reactions some examples of metals we have copper lead nickel and steel some non-metals on our periodic table is sulfur carbon bromine and oxygen and three of our semi-metals that we can find on the periodic table is boron silicon and geranium now some important information or terminology to remember to help understand the information we will further discuss are the following terms the first one is an atom an atom is considered the smallest building block of matter and an atom cannot be broken down by chemical methods our next one is an element important to remember that an element is a substance made up of only one type of atom compounds compounds can be considered to be two or more different atoms or elements that are chemically bonded with one another an example is to form a new substance when they bond together a new substance will be able to be formed a diatomic molecule these are two of the same atoms which are bonded with one another in gaseous phase there are only seven diatomic molecules that are naturally bonded in a gaseous phase which is hydrogen oxygen nitrogen chlorine bromine iodine and fluorine the image presented below under diatomic molecules is an oxygen diatomic molecule as you can see there a hydrogen molecule will consist of two atoms in gaseous phase that have bonded together remember you must be able to identify the difference between the terminology that we have just discussed so atoms are our single particles or our building blocks of matter molecules can either be molecules of elements molecules of compounds and compounds it is the bonding of two or more atoms together to form a new substance something important to remember when we start discussing chemical reactions is the types of bonds that form during a chemical reaction starting with the first one over here we have a metallic bond a metallic bond occurs between two types of metals or two metals the electrons it forms a sea of electrons and an example is copper our next type of bond is a covalent bond and a covalent bond occurs between a non-metal and a non-metal that are bonding together the electrons in a covalent bond are shared between the two elements that play a role in the compound and an example can be carbon dioxide our last one which you must be able to identify is an ionic bond an ionic bond occurs between a metal and a non-metal and the electrons are transferred during this chemical reaction an example is sodium chloride now when we start with this section you must be able to name a compound given to you there are certain steps which you need to follow the first one is to write the name of each symbol found in the compound step two is to identify the bond that is present then step three we have two specific rules the first element's name does not change at all but the second element ends with a suffix of i d e if the bond is covalent there is a fourth rule that comes into play or a fourth step that comes into play the second element will receive a prefix of either mono die or try in this level of physical sciences that prefix is determined by the number of atoms found in the second elements in the compound let's have a look at how to name compounds so we have given you two examples here let's start with carbon dioxide step one is to write the name of each compound of each symbol we have carbon and we have oxygen the ratio to bring vaccine past knowledge is one carbon is bonded to two oxygen step two is to identify the bond carbon is a non-metal and oxygen is a non-metal so it is a covalent bond step three the first element does not change the first bit of our compound will be carbon the second element gets an i and the second element gets a prefix because there are two oxygens present so example one for co2 the name will be carbon dioxide our second example is nacl common name for nacl which we'll discuss later on is sodium chloride step one is to identify each element present so we have sodium and we have chlorine the ratio here is one sodium to one chlorine step two is to identify the bond the bond we have here is an ionic bond step three is the first element's name does not change so we keep it as sodium and the second element ends in an eye so example two here will be sodium chloride remember we do not add any prefix to the chloride because this is an ionic bond the only time a prefix is added is in a covalent bond so let's have a have a look at an example of naming covalent bonds so the example is so3 step one is to identify what type of bond is present this is a covalent bond because s is a non-metal and o is a non-metal step two is to give the names of the elements playing a role in this compound the s represents sulfur and the o represents oxygen step three is to give the second element the suffix of i'd so step three is sulfur oxide and step four is to give the prefix remember we are adding a prefix as they are three oxygen molecules present so it is sulfur trioxide if we have a look at a few examples of ionic compounds we'll start with the first one which is fe2o3 step one is to identify what type of bond is present this is an ionic bond step two is to identify the elements that play well in this compound we have fe which represents iron and we have o which represents oxygen step three is to write out the name of the second element ending in and this is our final step we are not adding a 3 or looking at the 3 or 2 at all in this example because it is an ionic compound if we have a look at another ionic compound an example here is kcl step one is to identify the bond which is an ionic bond reason for that is because we have a natal bonding with a non-metal step two is to identify the elements that play a role in this equation this compound and it is potassium for k and chlorine for cl step three is to give the second element the suffix of iide which gives us the results of potassium chloride now there are certain compounds which we give a common name to which means our naming rule does not apply to these certain compounds the first one is water if we were to make it a chemical name it would be hydrogen oxide but our common name for h2o is water for the rest of the examples as you can see nh3 the common name will be ammonia hcl is hydrogen chloride but we know it as hydrochloric acid h2so4 is known as sulfuric acid and hno3 is known as nitric acid now we are going to do the reverse of what we have just done and we are going to write the formula of a compound first step that we will do is write down the symbols the second step will be to identify the bond between the atoms that play a role in the compound step three is to identify what the valencies are the elements and that we can find on the periodic table and step four is to cross over the valencies of the elements let's have a look at an example let's have a look at an example on how to write the compounds so we have carbon dioxide step one is to write the symbols we have c for carbon and we have o4 oxygen step two is to identify the bond this bond is a covalent bond reason for this is because carbon and oxygen are both non-metals and they have bonded now step three is to determine the valency number of the atoms valency numbers will be above each group on the periodic table starting with group one with plus one group two is plus two group three is plus three group f four is plus or minus four group five is negative three group six is negative two and group seven is negative one or minus one group eight has a valency of zero as there are no outer um electrons in the outermost energy level to be able to bond with other electrons for a chemical compound to occur chemical reactions occur remember the transition metals which is this block over here will always be plus 2 except for iron which is f e and solvent mercury which is a g and h g which will have a valency of one so once you have identified where the valencies are we place it with the chemical symbol in the top right hand corner so carbon has a valency of plus four oxygen has a valency of negative two now step four is to cross over so what we are going to do we put this the symbols next to each other and um the two of oxygen gets crossed over to carbon and the four from um carbon gets crossed over to oxygen we simplify that which gives us c1 c1o2 remember the one can be omitted which means left out as it shows us there is only one carbon present and two oxygens if we go to another example which is sodium chloride the common name of sodium chloride is table salt which is normal salt that we would consume when cooking so first step is to write the symbols down which is n a and c alp this is an ionic bond which means it is the bond between a metal and a non-metal step three is to identify the valencies so sodium over here has a valency of plus one and chlorine has a valency of negative one so again the valences get written in the top right corner of our elements we cross them over so the one of n a goes this side and the 1 of cl goes that side so our chemical formula is na1 cl you will see that we write it as nacl as the 1 does not have to be written in it can be omitted as we know if there is no um number uh subscript underneath the elements it means that there is just one that is represented so let's have another look at an example this one is with magnesium and magnesium chloride so step one is to write out the elements that play a role in this compound so step one is ng and cl step two is to identify the bond this bond is an ionic bond as magnesium is a metal and chlorine is a non-metal step three is to write out our elements and including the valency number so magnesium has a valence number of plus two and chlorine has a valence number of negative one step four is to rewrite our symbols with their valencies and now we cross over so the plus two of magnesium crosses over to chlorine and the negative one of chlorine crosses over to magnesium so our final answer will look like this mg1 cl2 our last example involves lithium oxide so again step one is to identify the elements that play a role in this compound which is li and o step two is to identify the bond which again is an ionic bond because lithium is a metal and oxygen is a non-metal step three write out the element names including their valences so l i has a valency of plus one and oxygen has a valency of negative two step three rewrite the elements with the valences so we can now cross over l i with the positive one the positive one moves to oxygen and negative two of oxygen moves to lithium so our final product will be l i two o one thank you for coming to my lesson we'll see you for the next lesson