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Biology 120 Notes (Part 2) Continuing the Discussion of Atoms and Other Molecules

Isotopes

  • Isotopes deal with neutrons in the atom.

  • They differ in the number of neutrons.

  • Some isotopes spontaneously decay and release radiation.

  • Electrons are attracted to the nucleus; it takes energy to hold electrons in place.

  • Electrons determine chemical behavior of atoms.

Valence Electrons

  • The outermost energy shell is called the valence shell.

  • The octet rule is a rule describing how a valence shell can only hold eight electrons (unless the atomic number is two or less.)

Molecules

  • Molecules are atoms held together by chemical bonds.

Chemical Bonds

  • Molecular bonds contain energy.

  • Valence shells determine the bonding activity.

  • There are three types of covalent bonds which are called: ionic, covalent, and hydrogen.

Ionic Bonds

  • An ion is a charged atom.

  • An ionic bind forms when electrons are transferred from one atom to another.

  • Salts are sold substances that usually sperate and exist as individual ions in water.

Formation of Sodium Chloride

  • The first ring holds only two electrons

  • After the second ring and as more rings are created, they will hold eight electrons each.

Covalent Bonds

  • Covalent bonds are a type of bond that describes how electrons are shared.

  • Covalent bonds can either be polar or nonpolar.

Nonpolar and Polar Bonds

  • Electrons are not always shared equally.

  • Atoms may have different electronegativities.

  • Electronegatives describe the strength with which atoms pull electrons toward themselves.

  • In general, when moving up to the right on the periodic table, the higher the electronegativity.

Hydrogen Bonds

  • A hydrogen bond is a weak attraction between a slightly positive hydrogen atom and a slightly negative tom in another molecule.

Biology 120 Notes (Part 2) Continuing the Discussion of Atoms and Other Molecules

Isotopes

  • Isotopes deal with neutrons in the atom.

  • They differ in the number of neutrons.

  • Some isotopes spontaneously decay and release radiation.

  • Electrons are attracted to the nucleus; it takes energy to hold electrons in place.

  • Electrons determine chemical behavior of atoms.

Valence Electrons

  • The outermost energy shell is called the valence shell.

  • The octet rule is a rule describing how a valence shell can only hold eight electrons (unless the atomic number is two or less.)

Molecules

  • Molecules are atoms held together by chemical bonds.

Chemical Bonds

  • Molecular bonds contain energy.

  • Valence shells determine the bonding activity.

  • There are three types of covalent bonds which are called: ionic, covalent, and hydrogen.

Ionic Bonds

  • An ion is a charged atom.

  • An ionic bind forms when electrons are transferred from one atom to another.

  • Salts are sold substances that usually sperate and exist as individual ions in water.

Formation of Sodium Chloride

  • The first ring holds only two electrons

  • After the second ring and as more rings are created, they will hold eight electrons each.

Covalent Bonds

  • Covalent bonds are a type of bond that describes how electrons are shared.

  • Covalent bonds can either be polar or nonpolar.

Nonpolar and Polar Bonds

  • Electrons are not always shared equally.

  • Atoms may have different electronegativities.

  • Electronegatives describe the strength with which atoms pull electrons toward themselves.

  • In general, when moving up to the right on the periodic table, the higher the electronegativity.

Hydrogen Bonds

  • A hydrogen bond is a weak attraction between a slightly positive hydrogen atom and a slightly negative tom in another molecule.

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