Chemistry Notes - Atoms, Elements, Compounds (PDF)

PRIOR LEARNING/STARTER Students have good understanding of the three states of matter. ATOMS ELEMENTS & COMPOUNDS GRADE C/B/A  KEY WORDS Atoms Elements Molecules Compound Symbols formula Heterogeneous Homogeneous  Learning objectives Define and explain the mea...

PRIOR LEARNING/STARTER Students have good understanding of the three states of matter. ATOMS ELEMENTS & COMPOUNDS GRADE C/B/A  KEY WORDS Atoms Elements Molecules Compound Symbols formula Heterogeneous Homogeneous  Learning objectives Define and explain the meaning of an atom and a molecule (Grade C) Define and explain the meaning of elements their characteristics with examples(Grade B) Explain the meaning of a compound, giving their characteristics with exam examples (Grade A)  Learning objectives 1: Define and explain the meaning of an atom and a molecule (Grade C) How does atoms look like. 6 of 19 © Boardworks Ltd 2012 How many different substances? How many different substances can you think of? There are millions of different substances! What are they all made of? 7 of 35 © Boardworks Ltd 2008 All substances are made of atoms All substances are made of tiny particles called atoms. Many substances are made up of different types of atoms. hydrogen and oxygen atoms carbon and hydrogen atoms iron, aluminium, silicon, carbon, nitrogen, hydrogen, oxygen and boron atoms oxygen and sulfur atoms 8 of 35 © Boardworks Ltd 2008 What atoms are you made of? Atoms are the smallest part of an element. Different elements join together in different ways to make all the materials in the Universe, from rocks to air. Just like all materials other (%) in the Universe, sulfur (0.25%) humans are also potassium (0.35%) made of atoms. phosphorus (1%) Which atoms calcium (2%) do you think are nitrogen (3%) most common in hydrogen (10%) the human body? carbon (18%) oxygen (65%) 9 of 35 © Boardworks Ltd 2008 How big are atoms? Atoms have a diameter of about 0.00000001 cm, which is far too small to be seen with your eyes. However, microscopes called Scanning Tunnelling Microscopes allow scientists to see the outlines of atoms. In one glass of water there are around: 12,000,000,000,000,000,000,000,000 oxygen atoms 24,000,000,000,000,000,000,000,000 hydrogen atoms. 10 of 35 © Boardworks Ltd 2008 Atomic zoom 11 of 35 © Boardworks Ltd 2008 Who discovered the atom? 12 of 35 © Boardworks Ltd 2008 What are molecules? Molecules are made up of two or more atoms. Molecules can be formed by two atoms of the same element, or by atoms from two or more different elements. Oxygen is an element made up of oxygen atoms only. How many atoms are there in one oxygen molecule? Other elements that form molecules include hydrogen, nitrogen, chlorine and bromine. 13 of 35 © Boardworks Ltd 2008 Molecules of compounds Some compounds exist as molecules: Water is made of hydrogen and Carbon dioxide is made of carbon and oxygen atoms. What is the formula of oxygen atoms. What is the formula of carbon water? dioxide? 14 of 46 © Boardworks Ltd 2008  Atoms in elements and compounds Elements are substances made up of one type of atom only. The element, hydrogen, exists as molecules. Each hydrogen molecule is made up of two hydrogen atoms joined together. H H 15 of 46 © Boardworks Ltd 2008 TASK 1 Refer to Worksheet AFL TIME L.O 1: Define and explain the meaning of an atom and a molecule (Grade C) GREEN? YELLOW? RED?  Learning objective 2 Define and explain the meaning of elements their characteristics with examples(Grade B) What is an element? An element is a substance that is made of only one type of atom. Elements are the simplest substances in the universe. Copper is an Carbon is an Helium is an element made element made element made up of copper up of carbon up of helium atoms only. atoms only. atoms only. 19 of 35 © Boardworks Ltd 2008 Who discovered the elements? Some elements, such as silver and gold, have been known about and used by people for centuries. However, many of the elements were only discovered in the 18th and 19th century. For example, British scientist Joseph Priestley discovered oxygen when he experimented with heating gases. Other scientists, such as Humphrey Davy, used electrolysis to isolate elements such as sodium and potassium for the first time. At the start of the 20th century, Marie Curie and other scientists discovered radioactive elements like polonium and francium. Which countries were these elements named after? 20 of 35 © Boardworks Ltd 2008 How many elements are there? There are currently 117 elements that have been discovered, 94 of which are naturally occurring. The remaining 23 elements only exist under laboratory conditions. How many naturally-occurring elements can you name? 21 of 35 © Boardworks Ltd 2008 How are artificial elements made? The first element to be artificially created was technetium, which was discovered in 1937 by Italian scientists working with the naturally-occurring element molybdenum. Since then, other artificial elements have been made in particle accelerators. CERN is one of the world’s largest particle accelerators. It is situated underground on the French-Swiss border and is run by scientists from all over Europe. Most artificial elements are very unstable and usually only exist for milliseconds before they decompose. 22 of 35 © Boardworks Ltd 2008  Examples of some elements METALS ◆NON- METALS S. NAME SYMBOL PHYSICAL NAME SYMBOL PHYSICAL No STATE STATE 1 Aluminium Al Solid Argon Ar Gas 2 Calcium Ca Solid Bromine Br Liquid 3 Copper Cu Solid Carbon C Solid 4 Iron Fe Solid Chlorine Cl Gas 5 Magnesium Mg Solid Silicon Si Solid 6 Mercury Hg Liquid Sulphur S Solid 7 Potassium K Solid Hydrogen H Gas 8 Sodium Na Solid Iodine I Solid 9 Zinc Zn Solid Nitrogen N Gas 10 Gold Au Solid oxygen O Gas ◆* Physical states are given at room temperature. 23 23 of 46 © Boardworks Ltd 2008 Characteristics of elements Element consist of unique type of atoms. Element cannot be further broken into simple substance by any chemical or physical means. Elements are building blocks of matter. Each element is given a unique chemical symbol (one or two letters). 24 24 of 46 © Boardworks Ltd 2008 25 Elements A sample of sodium atoms (Na). All atoms in the sample consist of sodium atoms, so the substance is homogeneous. A sample of chlorine molecules (Cl2). All atoms in the sample consist of chlorine atoms joined in pairs , so the substance is homogeneous. 25 of 46 © Boardworks Ltd 2008 The periodic table All the known elements are shown in the periodic table. Can you spot any patterns in how the elements are arranged in the periodic table? 26 of 46 © Boardworks Ltd 2008 TASK 2 Refer to Worksheet AFL TIME L.O 2: Define and explain the meaning of elements their characteristics with examples(Grade B) GREEN? YELLOW? RED?  Learning objective 3 Explain the meaning of a compound, giving their characteristics with examples (Grade A) Atoms joining to make compounds When two or more different elements react in a chemical reaction, the atoms do not just mix together, they become joined to one another 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. 30 of 36 © Boardworks Ltd 2008 Characteristics of a compound Compounds have very different properties to the elements from which they are made. This is because the atoms are joined together differently. carbon oxygen carbon dioxide (element) + (element) (compound) 31 of 46 © Boardworks Ltd 2008 Making a compound – iron sulfide Iron sulfide is produced from the reaction between iron and sulfur. iron + sulfur iron sulfide + 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? 32 of 46 © Boardworks Ltd 2008 Making a compound – water Water is produced from the reaction between hydrogen and oxygen. hydrogen + oxygen water + 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? 33 of 46 © Boardworks Ltd 2008 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? 34 of 46 © Boardworks Ltd 2008 Characteristics of compound It is a pure substance. It is always homogenous Compounds can be represented by a FORMULA, eg sodium chloride NaCl, methane CH4 and glucose C6H12O6 There must be at least two different types of atom (elements) joined together for a substance to be called a compound. Have a fixed composition and therefore a fixed ratio of atoms represented by a fixed formula Compounds are not easily separated by physical means.. 35 35 of 46 © Boardworks Ltd 2008 Examples of some compound S.No. COMPOUND FORMULA 1 Water H2O 2 Sodium hydroxide NaOH 3 Calcium carbonate CaCO3 4 Ethanol C2H5OH 5 Sulphuric acid H2SO4 6 Barium nitrate Ba(NO3)2 36 36 of 46 © Boardworks Ltd 2008 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 magnesium oxide sodium and chlorine sodium chloride oxygen and iron iron oxide 37 of 36 © Boardworks Ltd 2008 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) 38 of 36 © Boardworks Ltd 2008 Naming compounds containing 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”. element 1 element 2 element 3 compound nickel sulfur oxygen nickel sulfate magnesium nitrogen oxygen magnesium nitrate sodium nitrogen oxygen sodium nitrate copper sulfur oxygen copper sulfate aluminium bromine oxygen aluminium bromate 39 of 36 © Boardworks Ltd 2008 Writing a word equation 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. reactant 1 + reactant 2 product 1 + product 2 40 of 36 © Boardworks Ltd 2008 Completing word equations 41 of 36 © Boardworks Ltd 2008 Recognising elements and compounds 42 of 46 © Boardworks Ltd 2008 Element or compound? 43 of 46 © Boardworks Ltd 2008 TASK 3 Refer to Worksheet AFL TIME L.O 3: Explain the meaning of a compound, giving their characteristics with examples (Grade A) GREEN? YELLOW? RED? Plenary I am able to define an atom, element and a compound List 10 examples each of substances that are elements and compounds.