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Electrons and Chemical Bonding

Electrons and Chemical Bonding. Elements are compounds what letters are to words 26 letters make up all the words we know. Chemical bonding Joining of atoms to form new substances (molecules or chemical formulas

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Electrons and Chemical Bonding

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  1. Electrons and Chemical Bonding

  2. Elements are compounds what letters are to words • 26 letters make up all the words we know

  3. Chemical bonding • Joining of atoms to form new substances (molecules or chemical formulas • The new compounds (Substances) have different properties than the elements they are made up of

  4. Chemical bond • An interaction that holds 2 atoms together • Chemical bonds form when electrons are shared, gained, or lost

  5. Remember… • # of electrons = # or protons (atomic #) • Each energy level needs to be complete in order to be called stable • Valance electrons • Electrons in the outermost energy level • Can be shared or traded to become stable

  6. Drawing Valance Electrons “Lewis Dot Diagrams” • Magnesium • Neon • Aluminum • Sulfur • Argon

  7. Within a group or family elements have similar characteristics based on their # of valance electrons • See page 4 for rules • Group 1-1 • Group 2-2 • Group 3-12 no rule • Group 18- 8 (except helium 2)

  8. The # of electrons in outermost energy level determines whether an atom will form bonds • Atom in group 18 (noble gases) usually don’t form bonds • Why? • Stable outer energy level is full

  9. Atoms with less than 8 valance electrons: • Gain lose or share electrons to become stable • Sulfur (6 valance electrons) • Can share 2 or gain 2 • H, He, and Li are stable with 2 electrons in the 1st energy level • Be can lose 2 electrons and become stable

  10. Ionic Bonds • Bonds that form when electrons are transferred from one atom to another • Metals give electrons (becomes positive ion) • Nonmetals take electrons (becomes negative ion)

  11. Ions: • Charged particles that form when atoms gain or lose electrons • Draw NaCl

  12. The # of electrons lost from a metal element must balance with those gained by the nonmetal • These charges cancel out • The oppositely charged ions bond and become a 3D crystal lattice (strong attraction)

  13. Energy is needed to pull electrons from atoms • Nonmetals have nearly full energy level • They gain electrons to be stable • Oxygen needs 2 electrons • If gains 2 it becomes -2 oxide ion • “ide” is ending of ions that change by gaining electrons and have a negative charge

  14. Covalent and Metallic Bonds • Covalent Bonds: • Bonds formed when atoms share electrons to become stable • Form between nonmetals • They share because it takes a lot of energy to remove an electron from outermost energy level

  15. Compounds with covalent bonds have low melting and boiling points, brittle in solid state (can be liquid, solid, or gas)

  16. Form molecules: 2 or more atoms joined in a definite ratio. • Smallest unit of a compound that has all the properties of that compound

  17. Simplest molecules: • Molecules made of 2 covalently bonded atoms of the same element are called diatomic molecules • Elements found in nature of diatomic molecules are called diatomic elements • H2, O2, N2 and halogens (Cl2, F2, B2, I2) • They share valance electrons to become stable

  18. Complex molecules: • Carbon atoms form the base of many complex molecules because it can form up to 4 bonds with other elements. • Plastics, carbohydrates, petroleum

  19. Metallic Bonds: • A bond formed by attraction between positively charged metal ions and the electrons in the metal • Positive metal ions form when atoms lose electrons

  20. Metal atoms are packed so closely their outer energy levels overlap allowing valance electrons to move throughout the metal • The electrons cancel the + charge of the ions • Metallic bonds give metals their properties • Conductivity, malleability, ductility • Bonds remain even if shape changes

  21. Questions:1. Which of the following type of bonds deals mostly with metals?a) Ionic Bondsb) Metallic Bondsc) Covalent Bondsd) Polar Covalent Bonds2. What is the difference between an ionic bond and a covalent bond?3. Ionic bonds can be basically explained as:a) an attraction between two oppositely charged ionsb) an attraction between two like charged ionsc) sharing between a pair of electronsd) electrons are very tightly bound with the nucleus

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