Bonding
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Bonding. Formulas. Chemical formulas Tell us what elements a compound contains and the exact number of the atoms of each element in a unit of that compound Examples: SiO 2 1 atom of Silicon 2 atoms of Oxygen CH 3 COOH 2 atoms of Carbon 4 atoms of Oxygen 2 atoms of Oxygen.

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Formulas
Formulas

  • Chemical formulas

    • Tell us what elements a compound contains and the exact number of the atoms of each element in a unit of that compound

  • Examples:

    • SiO2

      • 1 atom of Silicon

      • 2 atoms of Oxygen

    • CH3COOH

      • 2 atoms of Carbon

      • 4 atoms of Oxygen

      • 2 atoms of Oxygen


Electron dot structures
Electron Dot Structures

  • Show only the electrons in the outer energy level of an atom

    • Electrons also called valence electrons

  • Chemical symbol surrounded by dots representing its outer electrons


How do you know how many dots to make
How do you know how many dots to make?

  • Group 1 – 1 outer electron

  • Group 2 – 2 outer electrons

  • Group 3 – 12 – varies

  • Group 13 – 3 outer electrons

  • Group 14 – 4 outer electrons

  • Group 15 – 5 outer electrons

  • Group 16 – 6 outer electrons

  • Group 17 – 7 outer electrons

  • Group 18 – 8 outer electrons


Chemical stability
Chemical Stability

  • An atom is chemically stable when its outer energy level is complete.

  • Atoms need 8 electrons to become stable.

    • Exception – Hydrogen and Helium need only 2 electrons.

  • Noble gases

    • Stable since they have a complete outer energy level


Chemical bonding
Chemical Bonding

  • Atoms with partially stable outer energy levels can gain, lose, or share electrons to obtain a stable outer energy level.

  • They combine with other partially stable outer energy levels to get 8 electrons

    • They become stable.

  • An attraction forms between the atoms, pulling them together to form compounds

  • Chemical bonds – the force that holds atoms together in a compound


Ions

  • Atoms lose or gain electrons which are called ions.

  • Ion

    • Charged particle since it has more of fewer electrons than protons

    • Loss of electrons – more protons

      • Called cations

    • Gain of electrons – less protons

      • Called anions



Ionic bonding the givers and takers
Ionic Bonding – The Givers and Takers

  • Transfer of electrons between a metal and a nonmetal

    • Metals – lose electrons and become a positive ion

    • Nonmetals – gain electrons and become a negative ion

  • The positive charge of the metal and the negative charge of the atom must be balanced.

    • The compound is neutral.


Covalent bonding the happy couple
Covalent Bonding – The Happy Couple

  • The sharing of electrons between two nonmetals

  • This sharing of electrons is called covalent bonding.

  • Types of bonds

    • Single bond – 2 shared electrons or 1 pair of electrons between atoms

    • Double bond – 4 shared electrons or 2 pairs of electrons between atoms

    • Triple bond – 6 shared electrons or 3 pairs of electrons between atoms


Metallic bonding sea of electrons
Metallic Bonding – “Sea of Electrons”

  • The positively charged metallic ions are surrounded by a cloud of electrons

    • Metallic ions are positively charged since metals tend to lose electrons.

  • Electrons move freely among the positively charged ions


Unequal sharing
Unequal Sharing

  • Electrons are not always shared equally between atoms in a covalent bond.

  • Strength of the attraction is related to

    • the size of the atom

    • the charge of the nucleus

    • the total number of electrons the atom has

  • Electrons that are unequally shared are held more closely to the atoms with the larger nucleus.


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