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General Biology: Atoms, Molecules, and Chemical Bonds

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  • What determines the chemical reactivity of an atom?

    The electrons in the outermost or valence shell determine an atom's chemical reactivity.
  • What is the maximum number of electrons in the first three electron shells?

    Shell 1 holds up to 2 electrons, Shell 2 up to 8 electrons, and Shell 3 up to 8 electrons.
  • What makes an atom stable?

    An atom is stable when its valence shell is full: 2 electrons in shell 1, 8 in shell 2, and 8 in shell 3.
  • What defines an element?

    The atomic number, which is the number of protons in the nucleus, defines an element.
  • What is the relationship between protons and electrons in a neutral atom?

    In a neutral atom, the number of protons equals the number of electrons.
  • How do atoms achieve stability through chemical bonds?

    Atoms with incomplete valence shells interact by sharing, donating, or receiving electrons to complete their outer shells.
  • What are ionic bonds?

    Ionic bonds form between ions with full positive or negative charges due to electron transfer.
  • What are covalent bonds?

    Covalent bonds involve sharing of outer electrons between atoms; they can be polar or nonpolar.
  • What is the difference between polar and nonpolar covalent bonds?

    Polar covalent bonds have unequal electron sharing with partial charges; nonpolar covalent bonds share electrons equally.
  • What is electronegativity?

    Electronegativity is an atom's ability to attract shared electrons; higher electronegativity means stronger pull.
  • Which atoms are highly electronegative?

    Oxygen and Nitrogen are highly electronegative atoms.
  • What type of bond forms between hydrogen (H) and chlorine (Cl) with electronegativities 2.1 and 3.0 respectively?

    A polar covalent bond forms due to an electronegativity difference of 0.9.
  • What is the octet rule?

    Atoms tend to gain, lose, or share electrons to have 8 electrons in their valence shell for stability.
  • How many covalent bonds can carbon form and why?

    Carbon has 4 valence electrons and forms 4 covalent bonds to complete its octet.
  • What is a double bond in covalent bonding?

    A double bond involves sharing two pairs of electrons between two atoms.
  • What is a triple bond in covalent bonding?

    A triple bond involves sharing three pairs of electrons between two atoms.
  • What is the difference between oxidation and reduction in redox reactions?

    Oxidation is the loss of electrons; reduction is the gain of electrons.
  • What is the significance of valence electrons in chemical bonding?

    Valence electrons determine how atoms interact and bond to form molecules.
  • What is the structure of a water molecule (H2O)?

    Two hydrogen atoms and one oxygen atom are joined by single covalent bonds forming a polar molecule.
  • What is the composition of sodium chloride (NaCl)?

    NaCl is formed by ionic bonding between sodium cations (Na+) and chloride anions (Cl-).