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Year 9 Science Revision Unit: Elements NGA PUMOTU O PAPATUANUKU/ ELEMENTS OF THE EARTH’S CRUST Key words: element atomic number molecule mixture neutron nucleus compound proton atom electron Key definitions to learn: element compound molecule mixture physical property atom electron proton neutron a pure substance composed of only one type of atom a pure substance composed of more than one type of atom two or more atoms chemically combined in a fixed ratio two or more elements or compounds that are easily separated can be seen or tested without changing the substance the smallest particle of matter to exist on its own a negative sub-atomic particle that orbits the nucleus a positive sub-atomic particle that is found in the nucleus a neutral sub-atomic particle that is found in the nucleus Key Learning Points: All Matter is made up of atoms. Each element differs from another by having a unique number of protons and electrons. Elements and their symbols. The symbols and names of the first 20 elements plus the common metals Fe, Cu, Zn, Ag, Sn, W, Pt, Au, Hg, Pb need to be MEMORISED. Here is a Periodic Table from which to get them . 1 Year 9 Science Revision Unit: Elements The Periodic Table 1. Each column in a periodic table is called a group. Elements in a group have similar chemical reactions. 2. Each row in a periodic table is called a period. As you move across a period, the number of electrons increases until the electron shell is full at the end of the period. Distinguishing between metals and non-metals 3. Metals are found on the left hand side of the Periodic Table, while non-metals are found on the right hand side of the Periodic Table. A line which steps down the periodic table divides the metals from the non-metals. The line starts between Beryllium and Boron. 4. Physical properties are used to distinguish between elements that are metals and elements that are non-metals. These properties are summarised in the table. Physical Properties Metals Non-metals solid at room temperature, except Hg can be either solid or gas but only Br is a liquid shiny when scratched dull when scratched bendy (malleable) are brittle, not bendy can be pulled into wires (ductile) are not ductile good conductors of heat poor conductors of heat good conductors of electricity poor conductors of electricity grey in colour except for Au and Cu colourful Formulae of elements and compounds Elements Hydrogen gas Oxygen gas Magnesium metal Zinc metal Nitrogen Sulfur H2 O2 Mg Zn N2 S8 Compounds Water Carbon dioxide Hydrochloric acid Copper sulphate Sodium Chloride Magnesium oxide H2O CO2 HCl CuSO4 NaCl MgO Number of atoms in molecules of elements and compounds Molecule MgCl2 CaCO3 Al(OH)3 Number of each atom One Mg and two Cl atoms One Ca, one C, and 3 O atoms One Al, 3 O, and 3H atoms Total atoms 3 5 7 2 Year 9 Science Revision Unit: Elements Atomic structure Here is a diagram showing the structure of an Carbon atom Atomic notation Particles in an atom Proton Neutron Electron charge positive neutral negative Where in the atom is it found? nucleus nucleus orbiting in energy levels What does the number of protons tell us? Atoms of different elements have a specific number of protons in their nucleus. The number of protons inside an atom is called the atomic number The atomic number is the smaller number next to the element on the Periodic Table. e.g All atoms of Na have a proton number of 11 i.e. they have 11 protons 11Na How can we tell how many neutrons there are in a nucleus? The number of protons + the number of neutrons is called the mass number. To find the number of neutrons in an atom of an element: No. of neutrons = mass no. – no. of protons 23 Na The mass number is the larger number next to the element on the Periodic Table How can we tell how many electrons there are in an atom? The number of electrons is always equal to the number of protons so the atom is neutral. 3 Year 9 Science Revision Unit: Elements No. of protons = no. of electrons Using atomic notation to determine its parts Elements Atomic Number of Number Protons Hydrogen 1 1 Carbon 6 6 Neon 10 10 Aluminium 13 13 Potassium 19 19 Gold 79 79 Mass Number 1 12 20 27 39 197 Number of neutrons 1–1=0 12 – 6 = 6 20–10 = 10 27–13 = 14 39 -19 = 20 197-79 = 88 ELEMENT - is made up of only one type of atoms cannot be broken down into a simpler type of matter can exist as either atoms (e.g. Ar argon) or molecules (e.g N2 nitrogen). COMPOUND - Is made up of two or more types of atoms bonded together. Can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means), Has properties that are different from its component elements. NaCl(table salt), Na is a reactive silver metal, Cl2 a poisonous green gas always contains the same ratio of its component atoms. MIXTURE consists of two or more different elements and/or compounds physically intermingled, - can be separated into its components by physical means, and - often retains many of the properties of its components. Salty water tastes of salt. - 4 Year 9 Science Revision 1. Complete the table and give the Symbol Name H F N S O Unit: Elements Revision Questions: name for each element symbol: Symbol Name Li Cl Ne He Al 2.Give the Symbol for each of these elements Name Symbol Boron Beryllium Argon Magnesium Phosphorus Name Calcium Potassium Carbon Silicon Sodium Symbol 3. Make 7 sentences by combining a word from each of the first 2 columns with a phrase from the 3rd column. For example : Atoms are small particles be broken down into anything simpler. Atoms Molecules are two (or more) elements or compounds mixed, but not joined, together. small particles. Elements can made when atoms join together. Compounds Mixtures cannot made from the chemical combination of 2 or more elements. made from only one type of atom. be separated into pure substances. 1. ______________________________________________________________________________ 2. ______________________________________________________________________________ 3. ______________________________________________________________________________ 4. ______________________________________________________________________________ 5. ______________________________________________________________________________ 6. ______________________________________________________________________________ 7. ______________________________________________________________________________ 5 Year 9 Science Revision Unit: Elements 4. Label the following diagrams as Element, Compound or Mixtures 5. Draw a diagram for each of the 2 atoms Nitrogen 14 Sodium 23 N 7 Na 11 6. Use the Periodic Table and your knowledge to complete the table Element Symbol Atomic Number of Number of Mass Number Protons electrons number Calcium 20 40 9 19 13 Potassium 19 39 Copper 29 7. Sort these elements into metal or non-metal: Na Ne K Cl Li F N Ca C Metals Non-metals Number of neutrons 14 35 Br 8. Calculate the number of atoms in each of the molecules Molecule Number of each atom NaCl NH4OH Al2(CO3)3 Total atoms 9. a. Decide whether the following two elements are metal or non-metal Magnesium: ____________________ Oxygen:______________________ b. Give 3 physical properties of Magnesium or Oxygen that helps you to decide 1. ________________________________ 2.________________________________ 3_______________________________________________________ 6 Year 9 Science Revision Unit: Elements Draw a mind map for this unit: Add to it, as you develop your learning. Elements Well done you have completed another revision unit. Now reflect on how you can improve further: Which aspects of the unit do I need to revise more carefully? Which aspects of the unit do I need help with? How will I seek this help? 7