Lesson 51 – What will be ionic and what will be covalent.ppt

Lesson 51 – What will be ionic and what will be covalent ? How could you tell whether a substance would be ionic or covalent from its constitutent elements ? How could you give some possible formulae of a substance from its constituent elements ? How could you tell whether a substance would be ionic or covalent from its constitutent elements ? Ionic substances are usually comprised of both metal and non-metal elements. e.g. NaCl, Mg(OH)2, K2Cr2O7, NaH.Exception : NH4Cl Covalent substances are usually comprised of non-metal elements. e.g. O2, CO2, C2H5OH. Summary of different Formulae (化學式) Formula (化學式) Chemical Shorthand Different kinds of formula Empirical formula (實驗式) Ionic formula (離子式) Molecular formula (分子式) Structural formula (結構式) Sodium chloride Sodium chloride Empirical formula – showing the simplest whole number ratio of atoms present. i.e. NaCl Ionic formula – showing the simplest whole number ratio of ions present. i.e. Na+Cl- Water Water Empirical formula – H2O Ionic formula – not applicable Molecular formula – showing the actual number of different atoms in a molecule. i.e. H2O Structural formula – showing the connection of the atoms in a molecule. Ethane Ethane Empirical formula – CH3 Ionic formula – not applicable Molecular formula – C2H6 Structural formula – ? What do different kinds of formula show ? Empirical formula– ? Ionic formula – ?? Molecular formula – Structural formula – ? What do different kinds of formula show ? Empirical formula– showing the simplest whole no. ratio of atoms present.? Ionic formula – showing the simplest whole no. ratio of ions present. ?? Molecular formula – showing the actual no. of different atoms in a molecule. Structural formula – showing the connection of atoms in a molecule. Summary Summary Predication of formula of substances Step 1 – Classify the atoms present : metal or non-metal. Step 2 – Decide whether it is an ionic, covalent (simple molecular or giant covalent) substance. Step 3 – Use t