Atomic Structure. OK, we know that all stuff is made up of the 92 naturally occurring. BUT what does each of these elements consist of?
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(2) Protons These are found at the centre or NUCLEUS of the atom (so they are nucleons). +. Electrons Are found at different distances around the nucleus. -. Neutrons Are also found in the nucleus of the atom (and are also nucleons). These are the simplest SUBATOMIC particles..
(3) The simple model of a hydrogen atom was proposed in 1913 by Niels Bohr. Extra: Investigate the life and work of this extremely influential physicist Things get more complicated with bigger atoms - which element is this an atom of?.
(4) Definitions: The PROTON NUMBER (AKA: Atomic Number) is the ___________________________________________________________ The proton number tells us which element the atom belongs to.. The NUCLEON NUMBER (AKA: Mass number) is the __________________________________________________________.
(5) Relative masses and charges of the simplest subatomic particles…. Sub-Atomic Particle. Relative Mass. Charge. Discovery. Proton. 1. +1. 1909 - Rutherford. Electron. 1/1836. -1. 1897 - JJ Thompson. 0. 1920 Rutherford suggests its existence/1932 James Chadwick discovers it. Approx 0. Neutron. 1. Discovery of the electron https://www.youtube.com/watch?v=Rb6MguN0Uj4 Discovery of the Nucleus https://www.youtube.com/watch?v=dNp-vP17asI. Videos: Basic Atomic Structure.
(6) Using symbols….. Write the symbols for the following elements…. Sodium. 23 11. Na. Helium. Calcium. IMPORTANT: By definition, an ATOM is always neutral so it must have the same number of _________________________ and __________________________ Video: Atomic Number Read pp22-23 Q1-3.
(7) ISOTOPES Why is Chlorine different from the rest of the elements in your periodic table?. Is reality, Chlorine exists as 2 different atoms…..
(8) Learn this definition: ISOTOPES of an element are atoms with the same proton number (same number of protons) and different nucleon numbers (different numbers of neutrons).. NB1. Isotopes of an element have the same chemical properties because chemical properties only depend on the number of electrons that an atom has! NB2. The physical properties of isotopes can be different, eg. density,. Explain why… _____________________________________________________________ ______________________________________________________________.
(9) ISOTOPES can be 2 types: radioactive and non-radioactive Radioactive isotopes are UNSTABLE and spontaneously break up to give other particles and radiation (which can be high energy and dangerous). Non-radioactive isotopes are STABLE (they do not change over time). Radioactive isotopes have very interesting properties and some important uses and applications: USES of Radioactive Isotopes Medical uses: To treat cancer - “radiotherapy”. Watch video: Isotopes in Medicine How are tracers used?.
(10) Non-medical uses - To find leaks in pipes - To kill germs and bacteria in food - Carbon dating - Fuel in nuclear power stations (U-235). Read pp24-25 Q1-3.
(11) Where do the electrons go in the atom? Electrons go into “shells” or “energy levels” around the nucleus. Each shell can take a maximum number of electrons, as shown in the following table: Shell *. How many electrons fit?. 1. 2. 2. 8. 3. 18. 4. 32. *This is the same as the PERIOD in the periodic table (the number down the left hand side or the number of the ROW that the element is in)..
(12) 1 2 3 4 5 6.
(13) At IGCSE level, we only have to be able to say where the electrons are for the first 20 elements. This is called the ELECTRONIC CONFIGURATION. 1. 2 2,2. 2,3. Etc. 2,1. 2,8 2,8,2. 2,8,3. Etc 2,8,8. 2,8,1 2,8,8,1. 2,8,8,2.
(14) NB1. The noble gases have a FULL OUTER SHELL of electrons and this makes them very STABLE and very UNREACTIVE. This is a important point! Name all of the noble gases. NB2. The electrons in the outer shell are called VALENCY ELECTRONS.
(15) You can easily see how many valency electrons an atom of an element has by looking at its GROUP NUMBER - the number at the top of the periodic table..
(16) Consider the following table:. Element. Symbol. # of Protons. # of # of Electronic configuration Electrons Neutrons. Hydrogen. H. 1. 1. 0. 1. Lithium. Li. 3. 3. 4. 2,1. K. 19. 19. 20. 2,8,8,1. Potassium. Read pp26-27 Q1-3 Video: Basic Atomic Structure Revision.
(17) Elements, Compounds and Mixtures Read pp28-29 Definition: What is an ELEMENT?. What are CHEMICAL BONDS?.
(18) What is a COMPOUND?. What is a MIXTURE?. YOU MUST LEARN THESE DEFINITIONS!. pp28-29 Q1-3.
(19) Put the following substances into the correct column in the table. Write their chemical formula if you know it… Hydrogen Water Cola Cao (or Nesquik as you prefer. Sobre los gustos…) Bromine Air Sodium Chloride Ammonia ELEMENT COMPOUND Crude Oil Petrol (Octane) Water Hydrogen Uranium Sodium Chloride Bromine Carbon dioxide Ammonia Uranium Nitrogen Petrol (Octane) Nitrogen Bleach Carbon dioxide Chlorine Chlorine Brass. MIXTURE. Cola Cao Air Crude Oil Bleach Brass.
(20) Metals and Non-Metals Read pp30-31 and compare and contrast the properties of metals and nonmetals in the following table… Metals. Non-Metals. Examples. Physical Properties. Chemical Properties. pp31-32 Q1-3/Questions pp32-33.
(21) Bonding - What holds stuff together Atoms usually form bonds with each other to become STABLE. There are exceptions to this in the periodic table. Which group of elements are already very stable? Why?. SO,…..when atoms take part in chemical reactions they do so in order to try to achieve the NOBLE GAS ELECTRONIC CONFIGURATION (NGEC).
(22) When chemicals react, new BONDS are formed between the particles involved. There are 3 types of bonding that we will come across: • Ionic Bonding • Covalent Bonding • Metallic Bonding.
(23) IONIC BONDING Ionic compounds form when metals (left hand side of periodic table) react with non-metals (right hand side of the periodic table). eg. Sodium and Chlorine What must Sodium do in order to achieve a stable NGEC?. A SODIUM ION is formed. NB. An ION is charged particle.
(24) What must Chlorine do to achieve a NGEC?. A CHLORIDE ION is formed. NB. When a non metal element forms a simple ion, it adopts the ending “ide”.
(25) So the electron from the Sodium atom is TRANSFERRED to the Chlorine atom. Once the oppositely charged ions have formed, what do they do?. NB: These diagrams are called “dot and cross diagrams” for obvious reasons. The use of dots and crosses is helpful to show where the electrons came from and where they have gone..
(26) Once lots of ions are formed, they come together to form a giant 3D structure…. This is called a crystal…...
(27) Now let’s do the same with another Group 1 and another Group 7 element. Lithium Fluoride, LiF is formed. Tricky example: Magnesium and Chlorine. Magnesium Chloride, MgCl2 is formed pp34-35 Q1-3.
(28) NB. In most cases you only need to show the outer shell of electrons - the valency shell - when you form ionic compounds IGCSE QUESTION:. The full diagram would look like this. But only outer shell electrons are required to get the marks.
(29) Key ideas: • Ions form when atoms lose or gain electrons to get a stable NGEC • Once the ions have formed the opposite charges attract to form an IONIC BOND • This causes the ions to line up to form a LATTICE of alternating positive and negative charges • Ionic bonds form between METAL IONS AND NON-METAL IONS. Once you can predict which ions will be formed by atoms of an element, you can use the information to work out the CHEMICAL FORMULAE of IONIC COMPOUNDS.
(30) In the following empty periodic table, fill in the ions formed by the elements…. 1. 0. H+ 2. 3. 4. 5. Al3+ P3Cu+ Zn2+ Cu2+. Ag+ Ba2+. 7. O2-. Na+ Fe2+ Fe3+. 6. Sn2+ Pb2+. Cl-.
(31) Try to predict the chemical formulae of the following: 1.Lithium Chloride. 2.Sodium Bromide. 3.Calcium Chloride. 4.Potassium Oxide. 5.Aluminium Fluoride. 6.Aluminium Oxide.
(32) The next type of bonding that exists in chemical elements and compounds is…. COVALENT BONDING In this type of bonding, atoms SHARE electrons with each other in order to achieve something closer to a NGEC. Hydrogen molecules. Chlorine Molecules. Definition: The VALENCY of an atom is the number of electrons that must be lost or gained in order to achieve a NGEC.
(33) Water molecules. Methane. Ammonia.
(34) Hydrogen Chloride. DEFINITION (LEARN):. pp36-37 Q1-3.
(35) More difficult covalent compounds…. Oxygen Nitrogen.
(36) Ethene. Methanol. Ethanol. Carbon Dioxide. Task - memorise the structures of the above molecules so that you can identify them in this online quiz.
(37) Structure and properties of IONIC and COVALENT COMPOUNDS We need to know the differences between ionic and covalent (sometimes called “molecular”) substances… Property. IONIC COMPOUNDS. COVALENT COMPOUNDS. Solubility in polar solvents (eg. water). High. Low. Solubility in non-polar (organic) solvents (eg. cyclohexane). Low. High. Volatility - is it volatile? (does it easily evaporate?). Low. High. Electrical conductivity when solid. Low. Low. Electrical conductivity when liquid or in solution. High. Low. Melting and boiling points. High. Low.
(38) Can we explain the differences in melting and boiling points of IONIC and COVALENT compounds?. A lot of energy is required to break down the strong ionic bonds in the giant 3D lattice so ionic compounds have a high melting point. Only weak intermolecular forces exist between covalent molecules so little energy is needed to melt and boil them!.
(39) pp40-41 Q1-3.
(40) MACROMOLECULES. “Giant covalent structures”. What are allotropes? Definition:.
(41) GRAPHITE Description:. Black shiny solid Layers of Carbon atoms Each C atom joined to 3 others Hexagons formed Properties:. DIAMOND Description:. Transparent colourless crystals Each C atom joined to 4 others A tetrahedral structure formed A 3D giant lattice created Properties:. High mpt and bpt Conducts electricity Layers can slide over each other Uses:. Dry lubricant(locks) Pencil “lead” Motors and generators. SILICON DIOXIDE Description:. Similar to diamond Tetrahedral structure Each Si atom joined to 4 O atoms Each O atom joined to 2 Si atoms 3D giant lattice created Properties:. High mpt and bpt Very hard. Uses:. Cutting an drilling tools Jewellery. High mpt and bpt Hard. Uses:. Glass manufacture pp42-43 Q1-3.
(42) The last type of bonding that we need to look at, and is perhaps the most special is…. Metallic Bonding. Each metal atom donates its valency electrons to form a DELOCALISED SEA OF ELECTRONS. This sea of mobile electrons flows around a LATTICE OF POSITIVELY CHARGED METAL IONS.. NB. It is the attraction between the lattice of metal ions and the sea of electrons that holds the metal together - this is Metallic Bonding, and acts in all directions.
(43) We can use these ideas to explain the curious and wonderful properties that metals have. They conduct electricity because…. They conduct heat because…..
(44) They are malleable and ductile because…. The layers of ions can slide over each other and adopt new shapes. This is possible because the metallic bonding acts in all directions so is not broken as the lattice changes shape.. Other properties…. Many metals have high melting and boiling points as lots of energy is required to overcome the metallic bonding. Many are also hard and dense. pp44-45 Q1-3 End of chapter questions.
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