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Year 10 Science Revision Booklet ATOMIC STRUCTURE REVISION AND QUESTIONS 2015 Key words: element nucleus molecule neutron atom proton mass number electron energy level ion formula compound atomic number mass number Key definitions to learn: Element Atom Molecule Compound Atomic number Mass number An element consists of one type of atom. An atom is made of protons and neutrons in a nucleus surrounded by electrons which orbit the nucleus in energy levels (shells). An atom is the smallest particle that can take part in a chemical reaction without be permanently changed Group of non-metal atoms bonded (joined) together e.g. H2 or H2O Two or more different elements bonded together e.g.. NaCl or H2O The number of protons in the nucleus of an atom. The number of protons added to the number of neutrons in the nucleus Key Learning Points: What is an element? An element contains one type of atom. How do we represent elements? An element is represented by a symbol. The symbols are shown on the Periodic Table. The metals are on the left side and non-metals on the right. e.g. S = sulphur, Na = sodium, C = carbon, Cu = copper, Cl = chlorine, Ca = calcium Some elements exist in pairs as molecules and are represented by a formula e.g. F2, Cl2, Br2, I2, H2, N2 and O2 Molecules are made of 2 or more non-metal atoms joined together. What is the structure of an atom like? Atoms consist of a positively charged nucleus with negatively charged electrons orbiting the nucleus. Inside the nucleus there are positively charged particles called protons and particles called neutrons, which are neutral. x proton Model of an atom: Draw in the protons and neutrons Be able to There are 2 electrons neutron label it! electron in an energy level x nucleus Year 10 Science Revision Booklet Particles in an atom Proton Neutron Electron Relative mass 1 1 1/1836 negligible Relative charge +1 0 -1 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 proton number or atomic number So each element has its own proton number ie. atomic number. The proton number is the smaller number next to the element on the Periodic Table. 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 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 if the atom is neutral. No. of protons = no. of electrons How are the electrons arranged in an atom? Electrons are arranged in energy levels around the nucleus of an atom An atom can hold a maximum number of electrons in each energy level 1st energy level = 2 electrons 2nd energy level = 8 electrons 3rd energy level = 8 electrons Atom Atomic Number (Proton Number) and Symbol Electron Arrangement Electron Diagram Electron diagrams show the arrangement of electrons in energy levels inside the atom. Beryllium 4Be 2,2 Carbon 6C Aluminium 13Al Na Year 10 Science Revision Booklet Atom Atomic Number (Proton Number) and Symbol Electron Arrangement Electron Diagram Fluorine 9F Oxygen 8O Chlorine 17Cl 2,7 Calculating Numbers of Sub-atomic Particles – protons, neutrons and electrons Element Symbol Mass Atomic number No. No. of No. of No. of Electron protons neutrons electrons arrangement (Proton number) Lithium Neon Magnesium Sodium Potassium Fluorine 7 20 23 39 3 10 19 9 3 10 12 11 12 2,8 9 10 11 19 What happens when elements react? Elements can react to form ions. Ions are charged atoms. o Metals form positive ions e.g. Na+ o Non-metals form negative ions e.g. ClThe oppositely charged ions join together to form a compound. How are electrons arranged in ions? Metal atoms lose electrons to form ions: Metal atom → Metal ion + electron lost Electron arrangement Electron diagram Atom = Na 2,8,1 e.g. Na → Na+ + ē Ion = Na+ [2,8]+ Year 10 Science Revision Booklet Non-metal atoms gain electrons to form ions: Non-metal atom + electron gained → Non-metal ion e.g. e.g. Cl + ē → ClIon = Cl[2,8,8]- Atom = Cl 2,8,7 Electron arrangement Electron diagram What is a Compound? A compound contains 2 or more elements bonded together. E.g. Sodium chloride contains sodium and chlorine. The properties of a compound are different to the properties of the elements it is made from. A compound is represented by its formula. E.g. sodium chloride has the formula NaCl. The formula shows how many of each type of atom are in the compound. Representing Compounds by Formulae Chemical name Chemical formula Elements present Number of atoms of each element Total number of atoms in the formula Sulfuric acid (sulphuric acid) H2SO4 Hydrogen Sulphur Oxygen 2xH 1xS 4xO 7 Magnesium oxide MgO Sodium hydroxide NaOH Magnesium fluoride MgF2 Sodium nitrate NaNO3 Ammonium nitrate (NH4)2 SO4 Calcium hydroxide Ca(OH)2 Year 10 Science Revision Booklet Naming Compounds You should learn some common compound names - e.g. H2SO4 = sulphuric acid H2O = water NaOH = sodium hydroxide HCl = hydrochloric acid CO2 = carbon dioxide You can work out the names of others. If there is a metal in the formula, name it first. e.g CaO is calcium oxide The non-metal part changes slightly: The symbol O is oxygen. In a compound it becomes oxide The symbol Cl is chlorine. In a compound it becomes chloride. The symbol F is fluorine. In a compound it becomes fluoride. The symbol Br is bromine. In a compound it becomes bromide. The symbol I is iodine. In a compound it becomes iodide. The symbol S is sulphur or sulfur. In a compound it becomes sulphide or sulfide. e.g. NaS = sodium sulfide Some groups of atoms have a special name i.e SO4 is sulphate or sulfate NO3 is nitrate HCO3 is hydrogencarbonate CO3 is carbonate Formula KCl FeO CuCO3 MgSO4 Name Potassium chloride Formula NaF CuS NaNO3 Zn(OH)2 OH is hydroxide Name How do we write Formulae for Compounds? To be able to write the formula for compounds we need to know the charges on the ions that are bonding. See Table of Ions on the back of the Periodic Table. The positive metal ions and negative non-metal ions combine in a certain ratio so that a neutral compound forms. e.g. Ca2+ can combine with 2 Cl- ions to form CaCl2 Combining method: Ca2+ Cl(2+) x 1 ( 1-) x2 2+ = 2Ca Cl2 Using the crossover method: Using the lego block method Ca2+ Cl- Ca2+ Cl- Cl- Ca1 Cl2 State the ratio of each ion in the compound and name the compound. Compound Name Formula MgSO4 CaF2 Na2O KNO3 Ca(OH)2 Ratio of ions 1Mg2+ : 1SO421Ca2+ : 2F- Year 10 Science Revision Booklet Write formulae for: Compound Calcium chloride Lead oxide Sodium sulfide Ions Ca2+ ClPb2+ O2Na+ S2- Formula Compound Iron hydroxide Sodium sulfate Lead oxide Ions Fe3+ OHNa+ SO42Pb2+ O2- Formula Website URL for revision: http://www.bbc.co.uk/schools/gcsebitesize/chemistry/classifyingmaterials/atomic_structure1rev1. shtml Draw a mindmap for this unit: Add to it, as you develop your learning. Atoms 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? Year 10 Science Revision Booklet