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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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