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Chemical Compounds

Chemical Compounds. Section 1: Ionic and Covalent Compounds Chemistry grade 9. Prepared by teacher: Ronak Ahmed Duhok International School 2012-2013. How compound forms?. When Ionic or molecules combine.

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Chemical Compounds

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  1. Chemical Compounds Section 1: Ionic and Covalent Compounds Chemistry grade 9 Prepared by teacher: Ronak Ahmed Duhok International School 2012-2013

  2. How compound forms? When Ionic or molecules combine The direct method to classify compounds depends on the type of chemical bonds in these compounds. What is Chemical bond? Is the force that bonds two or more atoms to form molecules or compounds

  3. Bonding can occur between valence electrons of different atoms What will determine if an Ionic compound or a covalent compound is formed? The behavior of valence electrons determine if an ionic compound or covalent compound is formed. Valence electrons: are electrons in the outermost energy level of an atom

  4. Ionic compound properties The properties of ionic compounds are a result of strong attractive forces called ionic bonds. Ionic bond : is an attraction between oppositely charged ions. Compounds that contain ionic bonds are called ionic compounds.

  5. How ionic compounds is formed? Ionic compounds can be formed by the reaction of metal with a nonmetal. • Example: The reaction between a metal (Na) and non-metal (Cl). The Sodium (Na) is the one who'll give the electron. The Chlorine (Cl) is the one who'll accept the electron.

  6. Metal atoms become positively charged ions when electrons are transferred from the metal atoms to the nonmetal atoms. Example: Sodium chloride (commonly known as table salt) is an ionic compound: (Na) will be Na+ (after give the electron) While (Cl) will be Cl- (after accept the electron)

  7. + - Cl Na reference

  8. Cl Na - + The attraction that occurred is ionic bond reference

  9. Brittleness • Ionic compounds tend to be brittle solids at room temperature. • They usually break apart when hit. • This property is due to the arrangement of ions in a repeating three-dimensional pattern called crystal lattice.

  10. Each ion in a lattice is surrounded by ions of the opposite charge. Hence, each ion is bonded to the ions around it. • What will happen to ionic compound when it hit? The pattern of ions changes. Ions that have the same charge line up & repeal one another, which causes the crystal to break.

  11. High melting points • Why most ionic compounds are solids at room temperature? ionic compounds have high melting points because of the strong ionic bonds that hold ions together. Example: solid sodium chloride must be heated to 801oC before it will melt.

  12. Solubility & Electrical conductivity • Many ionic compounds have a high tendency to be soluble. So they dissolved easily in water. • Water molecule attract each of the ions of an ionic compound and pull the ions away from one another. • The solution that forms when an ionic compound dissolves in water can conduct an electric current.

  13. Pure water Salt water

  14. How the solution can conduct electric current? Because ions are charged & are able to move freely past one another. However, an undissolved crystal of an ionic compound does not conduct an electric current.

  15. Covalent compounds and their properties • Most compounds are covalent compounds. • Covalent compound: a chemical compound formed by the sharing of valence electrons. • The group of atoms that make up a covalent compound is called a molecule Molecule: is the smallest particle into which a covalently bonded compound can be divided while retaining the same properties of the compound.

  16. Low solubility • Many covalent compounds do not dissolved well in water. • Did you ever notice that? • Ex: When you remove the cup of a soft drink. You will notice the carbon dioxide gas (CO2) that gives the soft drink its fizz eventually escapes, and the soft drink liquid goes “flat”.

  17. The attraction between water molecules is much stronger than their attraction to the molecules of most other covalent compounds. • Ex: During the preparation of salad dressing, you will see that oil & water don’t mix. • Note that the oil such as olive oil is made of covalent compounds.

  18. Low melting points why covalent compounds have much lower melting and boiling points than ionic compounds do? • The forces of attraction between molecules of covalent compounds are much weaker than the bonds holding ionic solids together. • Less heat is needed to separate the molecules of covalent compounds

  19. Electrical conductivity • Although most covalent compounds don’t dissolve in water, yet • Some do dissolve in water. Because the covalent compounds that dissolved in water form solutions composed of uncharged molecules. Such as Sugar ….…How? Are covalent compounds that dissolved in water can conduct electric current?

  20. Sugar is a covalent compound that dissolved in water and that does not form ions. So, a solution of sugar and water does not conduct an electric current. • However, some covalent compounds do form ions when they dissolve in water. Several acids, for example, form ions in water. These solutions, like ionic solutions, conduct an electric current.

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