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Chemistry C1a: Products from Rocks. Lesson 3: Molecules and Compounds Learning Objectives. Define a molecule and a compound Explain how chemical bond is formed Use molecular formulae to represent compounds. Definititions. A molecule ……………… A compound ………………. Bonding.
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Chemistry C1a: Products from Rocks
Lesson 3: Molecules and CompoundsLearning Objectives • Define a molecule and a compound • Explain how chemical bond is formed • Use molecular formulae to represent compounds
Definititions • A molecule ……………… • A compound ………………..
Bonding • Noble gases =unreactive found asatoms of elements • Some elements are found as molecules (e.g. oxygen O2, chlorine Cl2, bromine Br2, nitrogen N2 etc.) Atomsof the same elementchemically joined. • Most other elements (except……?) react to form COMPOUNDS • Compounds contain different types of atoms CHEMICALLY JOINED TOGETHER(BONDED) • Metal + non metal = IONIC BOND (metalTRANSFERSan electron to non metal) • Non metal + non metal = COVALENT BOND (atoms SHAREelectrons)
Demonstration Demonstration When sodium metalreacts with chlorine gas an _____ bond is formed. Sodium __________ an electron to chlorine . The sodium atom is missing an electron, so has a _______ charge. Chlorine has gained an extra electron and has a ________ charge. The IONS formed attract each other strongly. These bonds are very strong. negative transfers ionic positive
Bonding finding out about bonding.doc
Molecular formulae • When elements combine in a chemical reaction, they always combine in the same ratios • We can represent a compound with a molecular formula made up of the element symbols it is made from… • The number of atoms of an element is written as a SUBSCRIPT below the element symbol
Molecules, molecular formulae and displayed formulae • A molecule is a group of atoms joined together by chemical bonds. • A molecular formulashows the numbers of each type of atom in the molecule. • A displayed formulashows all the atoms and all the bonds in the molecule, (and which atoms are joined together.)
Lego Molecules Using the Lego bricks make the following compounds and write down their molecular formula.
CH4 N2 NH3 H2O ammonia water methane nitrogen Cl2 C2H6 CO2 chlorine ethane HCl O2 H2 carbon dioxide hydrogen chloride oxygen hydrogen