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Atoms, Bonding, and the Periodic Table: Exploring Chemical Bonds

This chapter explores the concepts of atoms, bonding, and the periodic table. It covers valence electrons, electron dot diagrams, chemical bonds, groups of elements, metalloids, ionic bonds, covalent bonds, bonding in metals, alloys, and metallic bonding.

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Atoms, Bonding, and the Periodic Table: Exploring Chemical Bonds

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  1. Chapter 5 Elements and Bonding

  2. 5.1 Atoms, Bonding, and the Periodic Table • Look at your table of elements… • With your partner, list 3 trends that you see. • Predict how elements actually combine to make compounds.

  3. Valence Electrons Valence Electrons: The electrons of an atom that are at the highest energy level, and are held onto the most loosely. *They determine the what the atom can bond to and what the atom cannot bond to.

  4. Electron Dot Diagram • Includes the given element and dots referring to each valence electron that the atom of that element has.

  5. Chemical Bond • Chemical Bond: When two atoms of an element or elements are attracted together by the rearrangement of electrons. • GOAL: to have 8 electrons in an atoms outer shell

  6. Chemical Bond/Chemical Reaction • When atoms bond, electrons may be transferred from one atom to another or shared between two atoms.

  7. Investigate • You now know characteristics of the Periodic Table. Predict the Groups on the table that would: • Transfer electrons • Share electrons • Never transfer or share electrons

  8. Groups of Elements • Elements within a group have similar characteristics, because they all have the same number of valence electrons.

  9. Investigate • How many valence electrons do the following have? • Alkali Metals • Alkaline Metals • Halogens • Noble Gases • What would you predict they would do to chemically react with other atoms?

  10. Metalloids • Have 6 valence electrons, so they can lose, gain, or share. Quartz crystal: made of silicon and oxygen. Vibrates at 32,000 vibrations per second.

  11. (5.2) Ionic Bonds • Ion: an atom that has an electric charge, either positive or negative. • What happens when Sodium (Na) loses an electron? • What if Na gained an electron?

  12. Ionic Bonds • Polyatomic charge: ions that are made of more than one atom.

  13. Ionic Bonds • Notice that Sodium Chloride (NaCl) is made when two elements become ions.

  14. Chemical Formula • Chemical Formula: The combination of symbols that show the ratio of elements in a compound. • Subscript • Reading (-ide –ate –ite)

  15. Ionic Bonds Calcium Carbonate

  16. Properties of Ionic Compounds • In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.

  17. (5.3) Covalent Bonds • Covalent Bond: Chemical bond formed when two atoms SHARE electrons.

  18. Covalent Bonds

  19. Double/Triple Bonds

  20. Molecular Compounds • Compared to ionic compounds, molecular compounds generally have lower melting points and boiling points, and they do not conduct electricity when dissolved in water.

  21. Unequal Sharing of Electrons • Atoms of some elements pull more strongly on electrons than do atoms of other elements. This causes a slight electrical charge. • Polar bond: covalent bond which shares electrons unevenly. • Nonpolar bond: covalent bond which shares electrons evenly.

  22. (5.4) Bonding in Metals • Guggenheim Museum in Bilbao, Spain • With your partner: why are metals used on buildings, furniture, automobiles, etc. What characteristics make them essential? Guggenheim Museum in Bilbao, Spain Titanium

  23. Bonding in Metals • Metals consist of positively charged metal ions in a “sea” of valence electrons.

  24. Characteristics • What can metals do? • Change of Shape • Conduct Electricity • Luster • Heat Conductivity

  25. Metals and Alloys • Alloy: a mixture made of two or more elements that has the properties of metal. In every alloy, at least one of the elements is a metal. • Alloys are less reactive with air and water than true metals. Trumpet: brass is a combination of copper and zinc

  26. Physical Properties • Alloys have different physical properties than pure metals. • Example: pure gold is very shiny, but soft. Gold is mixed with copper or silver to make it stronger.

  27. Chemical Properties • What happens to pure iron when left out too long? • Stainless steel: Iron with a mix of carbon, nickel, and chromium.

  28. Metallic Bonding • Most metals have 1, 2, or 3 valence electrons. • What would you predict the electrons of metals would do in order to bond with other elements? (talk to your partner) • When electrons are lost, the metal element becomes positively charged… Which is called a ??? • These positive and negative charges give metals their characteristics • “Sea of Electrons”

  29. Characteristics • Based on your knowledge of pure metals, and the charges that make them up, how do metals change shape and conduct electricity? (talk with partner)

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