The chemical context of life
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The Chemical Context of Life. Atomic structure The periodic table Chemical bonding Important elements in living organisms. A.Atomic Structure. Matter Anything that takes up space and has mass Atom The smallest stable particle of matter Composed of protons, neutrons, and electrons.

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The Chemical Context of Life

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The chemical context of life

The Chemical Context of Life

  • Atomic structure

  • The periodic table

  • Chemical bonding

  • Important elements in living organisms


A atomic structure

A.Atomic Structure

  • Matter

    • Anything that takes up space and has mass

  • Atom

    • The smallest stable particle of matter

    • Composed of protons, neutrons, and electrons


A atomic structure1

A. Atomic Structure

  • Protons

    • Positively charged

    • Atomic mass  1 atomic mass unit

    • Located in the nucleus of an atom

  • Neutrons

    • Electrically neutral

    • Atomic mass  1 atomic mass unit

    • Located in the nucleus of an atom


A atomic structure2

A. Atomic Structure

  • Electrons

    • Negatively charged

    • Atomic mass: very small, almost negligible

    • Located in electron shells (orbitals) around the nucleus

  • In a neutral atom, the number of electrons and protons is the same

  • Atoms can lose or gain electrons during chemical bonding


A atomic structure3

A. Atomic Structure

  • Element

    • A substance composed of only a single type of atom

    • Atomic number of an element

      • The number of protons in its atoms

      • The atomic number is the same for all atoms of an element

    • Mass number of an element

      • The number of protons plus the number of neutrons in its atoms

      • The atoms of an element may have a variable number of neutrons


A atomic structure4

A. Atomic Structure

  • Isotopes of an element

    • Different forms of an element with the same atomic number but with different mass numbers

    • The atoms of some isotopes are stable

    • Other isotopes are radioactive, having unstable atoms that spontaneously break apart (decay) to form other atoms

    • When radioactive atoms decay, energy is released


A atomic structure5

A. Atomic Structure

  • For example, carbon has three isotopes

    • Carbon-12, with 6 protons and 6 neutrons, is the most common form of carbon

    • Carbon-13, with 6 protons and 7 neutrons, is stable (non-radioactive) and rare

    • Carbon-14, with 6 protons and 8 neutrons, is unstable (radioactive) and rare


B the periodic table

B.The Periodic Table

  • In the periodic table

    • Elements are listed in order of their atomic numbers

    • Elements are designated by standard one or two-letter abbreviations

    • Elements in the same vertical column often have very similar chemical bonding properties


C chemical bonding

C.Chemical Bonding

  • Chemical bonding occurs when two or more atoms combine

  • Atoms combine by exchanging or sharing electrons in their outermost electron shell

  • Chemical compound

    • Formed when the atoms of two or more different elements combine by chemical bonding

    • Properties of a compound are usually very different than those of its elements


C chemical bonding1

C.Chemical Bonding

  • Ionic bonds

    • Formed when electrons are completely transferred from one atom to another

    • The atom that gains electrons becomes a negative ion (anion)

    • The atom that loses electrons becomes a positive ion (cation)

    • Example: Sodium chlorideNa + Cl  Na+ Cl–


C chemical bonding2

C.Chemical Bonding

  • Covalent bonds

    • Form when two atoms share one or more pairs of electrons

    • Molecule: consists of two or more atoms that are joined by covalent bonding

    • Covalent bonds are generally more stable than ionic bonds in aqueous (water) solution


C chemical bonding3

C.Chemical Bonding

  • Other types of atomic & molecular interactions

    • Polar interactions

      • Attraction between partially charged (polar) molecules and other polar or charged molecules

      • Similar to ionic bonding

    • Hydrogen bonding

      • Interaction between a hydrogen atom and two strong electronegative groups

    • Hydrophobic interactions

      • Attraction between molecules that are insoluble in water


D important elements

D.Important Elements

  • See table in the textbook

  • Major covalent constituents of biomolecules:C H N O P S


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