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Ch. 20 Chemical Bonds

Learn about the stability of elements on their own and in compounds, the formation of chemical bonds, and the properties of compounds. Understand the concepts of atomic stability and the octet rule.

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Ch. 20 Chemical Bonds

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  1. Ch. 20 Chemical Bonds Stability in Bonding Ch. 20 Section 1

  2. Bell Work • Good morning! Today is October 14. I hope you all had a great Fall Break! We are now on Chapter 20, Section 1 (page 602 in your book). Please get started on the Bell Work quietly. • 1). Explain why some elements are stable on their own while others are more stable in compounds? • 2). Describe why chemical bonding occurs. Give two examples of how bonds can form. • 3). Compare and contrast the properties of the individuals elements that combine to make salt with the compound salt. (NaCl)

  3. Answers • 1). If an element has eight electrons in its outer electron energy level, it has a tendency not to react. • 2). Electrons are either gained, lost, or shared between atoms. • 3). Sodium, as an elements, is a solid metal. Chlorine is a gas. When the two combine to form sodium chloride, they form a solid compound.

  4. Warm Up • Sodium is in group one of the periodic table. A sodium atom has one valence electron. Atoms with one electron in their outer energy levels will bond easily with atoms having 7 valence electrons. Name one element sodium could give its one extra electron to.

  5. Combining Elements • Many elements exist around you in their uncombined forms, but elements can unite chemically to form compounds when conditions are right

  6. Combining Elements • Compounds often have properties unlike the properties of their individual elements

  7. Combining Elements • A Chemical Formulatells what elements a compound contains and the exact number of atoms of each element in a unit of the compound

  8. Combining Elements • A subscript is written after and below the element’s symbol • Subscripts tell how many atoms are in each unit of a compound NH3

  9. Atomic Stability • An atom is chemically stable when its outer energy level is complete (like the Noble Gases) • Other elements are more stable when they can complete their outer energy levels by becoming part of a compound

  10. Atomic Stability • The Octet Rulesays that atoms tend to combine so they have 8 electrons in their outer energy level • Atoms can gain, lose, or share electrons to complete their outer energy levels and become stable • Gaining, losing, and sharing electrons forms an attraction between atoms

  11. Atomic Stability • The attraction is called a Chemical Bond, and atoms are pulled together, forming a compound

  12. Atomic Stability • Generally, ionic bonds are formed between a metal and a nonmetal, and covalent bonds are formed between two or more nonmetals • Electronegativity is the ability of atoms to attract electrons within a bond – this determines the bond type

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