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Odd-one-out. Combining elements. There are many different materials in the world, but only around 100 elements. These elements can be combined in many different ways to make thousands of compounds. Atoms in elements. An element is a substance made up of only one type of atom.
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Combining elements There are many different materials in the world, but only around 100 elements. These elements can be combined in many different ways to make thousands of compounds.
Atoms in elements An element is a substance made up of only one type of atom. Copper is made up of copper atoms only. Carbon is made up of carbon atoms only. Helium is made up of helium atoms only.
Molecules of elements hydrogen molecule = hydrogen atom = The atoms in some elements join together to make molecules. One of the elements that exists like this is hydrogen. Each hydrogen atom joins up with one other atom to make a hydrogen molecule. The formula of a hydrogen molecule is H2. Other elements such as nitrogen, oxygen, and chlorine also exist as molecules. What are the formulae of these elements?
Atoms joining to make compounds + hydrogen oxygen water + In a chemical reaction, the atoms in the reactants become joined in different ways and this is how new compounds are formed. When two or more elements react in a chemical reaction, the atoms do not just mix together, they become joined to one another to make compounds.
Molecules of compounds Some compounds exist as molecules: Water is made of hydrogen and oxygen atoms. What is the formula of water? Carbon dioxide is made of carbon and oxygen atoms. What is the formula of carbon dioxide?
A compound is not a mixture The molecules in a mixtureof hydrogen gas and oxygen gas look like this: But the molecules in water look like this… …because water is a compound, made when hydrogen and oxygen react and their atoms become chemically joined to each other.
Properties of elements and compounds Why is it safe to put sodium chloride on fish and chips… …but not safe to use sodium and chlorine?
Properties of a compound carbon (element) oxygen (element) carbon dioxide (compound) + Compounds have very different properties to the elements from which they are made. This is because the atoms are joined together differently.
Making a compound – iron sulfide + iron sulfur iron sulfide + Iron sulfide is produced from the reaction between iron and sulfur. One iron atom reacts with one sulfur atom to make one molecule of iron sulfide. Why does iron sulfide have different properties to the elements iron and sulfur?
Making a compound – water + hydrogen oxygen water + Water is produced from the reaction between hydrogen and oxygen. Two hydrogen atoms react with one oxygen atom to produce two molecules of water. Why are the properties of water different from the properties of hydrogen and oxygen?
Making a compound – magnesium oxide Magnesium oxide is produced from the reaction between magnesium and oxygen. + magnesium oxygen magnesium oxide + Two atoms of magnesium react with one molecule of oxygen to make two molecules of magnesium oxide. What are the differences in the properties of magnesium, oxygen and magnesium oxide?
Naming simple compounds To name simple compounds of metals and non-metals: 1. Write down the name of the metal. 2.Write down the name of the non-metal, changing the ending of the word to “-ide”. What is the name of the compound made when the following elements combine? • magnesium and oxygen • sodium and chlorine • oxygen and iron magnesium oxide sodium chloride iron oxide
Naming simple compounds What is the name of each compound formed by these metal and non-metal elements? element 1 element 2 compound iron (Fe) sulfur (S) iron sulfide (FeS) magnesium (Mg) nitrogen (N) magnesium nitride (Mg3N2) sodium (Na) chlorine (Cl) sodium chloride (NaCl) tin (Sn) oxygen (O) tin oxide (SnO) aluminium (Al) bromine (Br) aluminium bromide (AlBr3) nickel (Ni) iodine (I) nickel iodide (NiI2) zinc (Zn) sulfur (S) zinc sulfide (ZnS) lithium (Li) nitrogen (N) lithium nitride (Li3N)
Naming compounds containing oxygen element 1 element 2 element 3 compound nickel sulfur oxygen magnesium nitrogen oxygen sodium nitrogen oxygen copper sulfur oxygen aluminium bromine oxygen Many compounds contain more than two elements. For compounds containing two elements plus oxygen, the ending of the other non-metal usually changes to “-ate”. nickel sulfate magnesium nitrate sodium nitrate copper sulfate aluminium bromate
Writing a word equation + + reactant 1 reactant 2 product 1 product 2 A word equation can be used to describe any chemical reaction. The steps for writing a word equation are: 1. On the right-hand side, put the name(s) of the reactant(s). If there are two or more reactants, link them with a +sign. 2. In the middle, draw an arrow (). 3. On the right-hand side, put the name(s) of the product(s). If there are two or more products, link them with a +sign.
Composition of compounds two hydrogen atoms one oxygen atom A compound always contains a particular amount of each element. It has a fixed composition. For example, water molecules always contain twice as much hydrogen as oxygen. This is shown in its formula, H2O. What is the formula of carbon dioxide? How many of each atom does each carbon dioxidemolecule contain?
Writing a formula carbon atoms = 1 oxygen atoms = 2 formula = CO2 carbon dioxide hydrogen atoms = 2 oxygen atoms = 1 formula = H2O water A formula uses the symbols of the elements in a compound. When there is more than one atom of an element, the number is always written after the symbol. The formula shows the ratio of atoms in a compound.
What is the formula? What is the formula of each of these compounds? (remember when you write a formula,put the metal first) 1. Titanium oxide For every titanium atom there are two oxygen atoms. Formula = TiO2 2.Lithium oxide For every two lithium atoms there is one oxygen atom.Formula = Li2O 3.Aluminium chloride For every aluminium atom there are three chlorine atoms. Formula = AlCl3
Why do scientists use formulae? Elements and compounds have different names in different languages: • For example, sodium chloride is called: • Cloruro sódico in Spanish • Chlorek sodu in Polish • Хлорид натрия in Russian. This can lead to problems when scientists from different countries try to explain what they are investigating. However, because formulae are the same in every language, scientists can communicate their ideas easily using these instead of names.
