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Published byCurtis Nash Modified over 9 years ago
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Between different molecules Metal-Nonmetal Gain or loss of electrons Nonmetal-Nonmetal Sharing of electrons Within a compound (between elements) Unequal sharing of electrons Equal sharing of electrons Metals Surrounding sea of electrons When H bonds to N, O, F Occurs in proteins
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FORCES What is a chemical bond? The force that holds two atoms together
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● Intramolecular Force (stronger) holds elements together to make compounds ● Intermolecular Force (weaker) holds molecules together to form solids, liquids, and gases
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Intramolecular Force – The force within a compound between atoms. Example: the bond between O and H in a H 2 O molecule
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Example: the bond between Na and Cl in a NaCl molecules Na + Cl -
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● Ionic Bond (strongest) – electrostatic attraction between a metal and nonmetal that involves a gain or loss of electrons ● Covalent Bond – between two nonmetals that involves a sharing of electrons ● Metallic Bond – between metal atoms and the surrounding sea of electrons
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● Ionic Bond (strongest) – between a metal and nonmetal that involves a gain or loss of electrons ● When an atom loses a valence electron to another atom, it becomes a (+) ion. This is a CATION. ● When an atom accepts a valence electron from another atom, it becomes a (-) ion. This is an ANION.
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FULL OCTET
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Cl Na EXAMPLE 1 valence e- 7 valence e-
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Cl Na EXAMPLE 8 valence e- Cation – Na +1 Anion – Cl -1
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Ca 2+ S 2-
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Shows the # of valence elecrons the atom has What is the charge on Ca? 2+1- What is the charge on F? How many atoms of Ca and F are needed? DROP AND SWITCH THE CHARGES
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Ca 2+ F -1 Drop Ca 2 F 1 Switch CaF 2
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Drop Na 1 N 3 Switch Na 3 N 1+ 3-
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1. # of valence electrons in aluminum? 2. Change in electrons for octet? 3. Ionic charge of aluminum? 3 Lose 3 e - Al 3+
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● Sharing of electrons H-H = H 2
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● Polar Covalent Bond – electrons are unevenly shared; different EN values ● Nonpolar Covalent Bond – electrons are evenly shared; same or very close EN values
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Electronegativity is the tendency of an atom to attract other atoms’ valence electrons ● The more electronegative the atom, the stronger the attraction for electrons ● Fluorine is the most electronegative atom on the periodic table
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● Fluorine the Flirt likes to attract other atoms’ valence electrons Examples: H-F (polar) H-H (nonpolar)
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The O atom pulls on the shared electrons in each H causing a partial (+) charge on each H atom and partial (–) charge on the O atom Why is O pulling the electrons towards itself? O is more electronegative and attracts the electrons – unequal sharing of electrons Why does water act like a magnet? Because the (+) attracts the (-)
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● Free floating electrons among metals
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Intermolecular Force – The force between different molecules Example: an interstate highway runs between different states
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Intermolecular Force Intramolecular Force
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Intermolecular Force Intramolecular Force
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● Hydrogen Bond – when H bonds to N, O, or F o Important in DNA (genetic material), proteins, and water molecules ● Disulfide Bond – occurs in proteins to ensure proper functioning and prevent destruction from extreme environments ● Peptide Bond – occurs between amino acids in DNA.
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Single bond Share one pair of electrons Double bond Share two pairs of electrons
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● Why do atoms form chemical bonds? How? ● What does it mean when an atom is chemically unstable? ● What does the octet rule state? ● What subatomic particle is involved in forming chemical bonds? ● What is a molecule? ● How can the periodic table be used to determine the # of valence electrons? ● How can the periodic table be used to determine the # of energy levels? ● Most matter is electrically neutral, why? To become more stable by losing, gaining, or sharing electrons It does not have a full octet of electrons The outermost energy level has 8 valence electrons (full shell) Valence electrons Two or more elements chemically combined together Look at the group number (Transition Metals are different) Look at the period number The # of protons cancels out the # of electrons
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