Your SlideShare is downloading. ×
02  chemistry text
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

02 chemistry text

2,349

Published on

Basic Chemistry, Bonds, etc.

Basic Chemistry, Bonds, etc.

Published in: Education
0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
2,349
On Slideshare
0
From Embeds
0
Number of Embeds
10
Actions
Shares
0
Downloads
101
Comments
0
Likes
3
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. 1
    Chapter 2
    The Chemical Context of Life
  • 2. 2
    Matter
    Takes up space and has mass
    Exists as elements (pure form) and in chemical combinations called compounds
  • 3. 3
    Elements
    Can’t be broken down into simpler substances by chemical reaction
    Composed of atoms
    Essential elements in living things include carbon C, hydrogen H, oxygen O, and nitrogen N making up 96% of an organism
  • 4. 4
    Other Elements
    A few other elements Make up the remaining 4% of living matter
    Trace Elements
    Table 2.1
  • 5. 5
    Deficiencies
    (b) Iodine deficiency (Goiter)
    (a) Nitrogen deficiency
    If there is a deficiency of an essential element, disease results
    Figure 2.3
  • 6. 6
    Trace Elements
    Trace elements Are required by an organism in only minute quantities
    Minerals such as Fe and Zn are trace elements
  • 7. 7
    Compounds
    +
    Sodium
    Chloride
    Sodium Chloride
    Are substances consisting of two or more elements combined in a fixed ratio
    Have characteristics different from those of their elements
    Figure 2.2
  • 8. 8
    Properties of Matter
    An element’s properties depend on the structure of its atoms
    Each element consists of a certain kind of atom that is different from those of other elements
    An atom is the smallest unit of matter that still retains the properties of an element
  • 9. 9
    Subatomic Particles
    Atoms of each element Are composed of even smaller parts called subatomic particles
    Neutrons, which have no electrical charge
    Protons, which are positively charged
    Electrons, which are negatively charged
  • 10. 10
    Subatomic Particle Location
    Protons and neutrons
    Are found in the atomic nucleus
    Electrons
    Surround the nucleus in a “cloud”
  • 11. 11
    Simplified models of an Atom
    Cloud of negative
    charge (2 electrons)
    Electrons
    Nucleus
    This model represents the
    electrons as a cloud of
    negative charge, as if we had
    taken many snapshots of the 2
    electrons over time, with each
    dot representing an electron‘s
    position at one point in time.
    (a)
    In this even more simplified
    model, the electrons are
    shown as two small blue
    spheres on a circle around the
    nucleus.
    (b)
    Figure 2.4
  • 12. 12
    Atomic Number & Atomic Mass
    Atoms of the various elements Differ in their number of subatomic particles
    The number of protons in the nucleus = atomic number
    The number of protons + neutrons = atomic mass
    Neutral atoms have equal numbers of protons & electrons (+ and – charges)
  • 13. 13
    Atomic Number
    Is unique to each element and is used to arrange atoms on the Periodic table
    Carbon = 12
    Oxygen = 16
    Hydrogen = 1
    Nitrogen = 17
  • 14. 14
    Atomic Mass
    • Is an approximation of the atomic mass of an atom
    • 15. It is the average of the mass of all isotopes of that particular element
    • 16. Can be used to find the number of neutrons (Subtract atomic number from atomic mass)
  • 15
    Isotopes
    Different forms of the same element
    Have the same number of protons, but different number of neutrons
    May be radioactive spontaneously giving off particles and energy
    May be used to date fossils or as medical tracers
  • 17. 16
    Energy Levels of Electrons
    An atom’s electrons Vary in the amount of energy they possess
    Electrons further from the nucleus have more energy
    Electron’s can absorb energy and become “excited”
    Excited electrons gain energy and move to higher energy levels or lose energy and move to lower levels
  • 18. 17
    Energy
    Energy
    Is defined as the capacity to cause change
    Potential energy
    - Is the energy that matter possesses because of its location or structure
    Kinetic Energy
    - Is the energy of motion
  • 19. 18
    Electrons and Energy
    (a)
    A ball bouncing down a flight
    of stairs provides an analogy
    for energy levels of electrons,
    because the ball can only rest
    on each step, not between
    steps.
    Figure 2.7A
    The electrons of an atom
    Differ in the amounts of potential energy they possess
  • 20. 19
    Energy Levels
    Third energy level (shell)
    Second energy level (shell)
    Energy
    absorbed
    First energy level (shell)
    Energy
    lost
    Atomic
    nucleus
    (b)
    An electron can move from one level to another only if the energy
    it gains or loses is exactly equal to the difference in energy between
    the two levels. Arrows indicate some of the step-wise changes in
    potential energy that are possible.
    Figure 2.7B
    Are represented by electron shells
  • 21. Thermodynamics and Biology
    First law of thermodynamics
    In any process, the total energy of the universe remains the same.
    It can also be defined as: for a thermodynamic cycle the sum of net heat supplied to the system and the net work done by the system is equal to zero.
    Second law of thermodynamics
    The entropy (useless energy) of an isolated system will tend to increase over time.
    In a simple manner, the second law states that "energy systems have a tendency to increase their entropy" rather than decrease it.
    20
  • 22. 21
    Periodic table
    Helium
    2He
    Atomic number
    2
    He
    4.00
    Hydrogen
    1H
    Element symbol
    Atomic mass
    First
    shell
    Electron-shell
    diagram
    Beryllium
    4Be
    Carbon
    6C
    Oxygen
    8O
    Neon
    10Ne
    Lithium
    3Li
    Boron
    3B
    Nitrogen
    7N
    Fluorine
    9F
    Second
    shell
    Aluminum
    13Al
    Chlorine
    17Cl
    Argon
    18Ar
    Sulfur
    16S
    Sodium
    11Na
    Magnesium
    12Mg
    Silicon
    14Si
    Phosphorus
    15P
    Third
    shell
    Figure 2.8
    Shows the electron distribution for all the elements
  • 23. 22
    Why do some elements react?
    Valence electrons
    Are those in the outermost, or valence shell
    Determine the chemical behavior of an atom
  • 24. 23
    Electron Orbitals
    An orbital
    Is the three-dimensional space where an electron is found 90% of the time
  • 25. 24
    Covalent Bonds
    Hydrogen atoms (2 H)
    In each hydrogen
    atom, the single electron
    is held in its orbital by
    its attraction to the
    proton in the nucleus.
    +
    +
    1
    2
    3
    When two hydrogen
    atoms approach each
    other, the electron of
    each atom is also
    attracted to the proton
    in the other nucleus.
    +
    +
    The two electrons
    become shared in a
    covalent bond,
    forming an H2
    molecule.
    +
    +
    Hydrogen
    molecule (H2)
    Sharing of a pair of valence electrons
    Examples: H2
    Figure 2.10
  • 26. 25
    Covalent Bonding
    Name
    (molecular
    formula)
    Electron-
    shell
    diagram
    Space-
    filling
    model
    Structural
    formula
    Hydrogen (H2).
    Two hydrogen
    atoms can form a
    single bond.
    H
    H
    Oxygen (O2).
    Two oxygen atoms
    share two pairs of
    electrons to form
    a double bond.
    O
    O
    Figure 2.11 A, B
    A molecule
    Consists of two or more atoms held together by covalent bonds
    A single bond
    Is the sharing of one pair of valence electrons
    A double bond
    Is the sharing of two pairs of valence electrons
  • 27. 26
    Compounds & Covalent Bonds
    Name
    (molecular
    formula)
    Electron-
    shell
    diagram
    Space-
    filling
    model
    Structural
    formula
    (c)
    Water (H2O).
    Two hydrogen
    atoms and one
    oxygen atom are
    joined by covalent
    bonds to produce a
    molecule of water.
    H
    O
    H
    (d)
    Methane (CH4).
    Four hydrogen
    atoms can satisfy
    the valence of
    one carbon
    atom, forming
    methane.
    H
    H
    H
    C
    H
    Figure 2.11 C, D
  • 28. 27
    Covalent Bonding
    In a nonpolar covalent bond
    The atoms have similar electronegativities
    Share the electron equally
  • 29. 28
    Because oxygen (O) is more electronegative than hydrogen (H),
    shared electrons are pulled more toward oxygen.
    d–
    This results in a
    partial negative
    charge on the
    oxygen and a
    partial positive
    charge on
    the hydrogens.
    O
    H
    H
    d+
    d+
    H2O
    In a polar covalent bond
    The atoms have differing electronegativities
    Share the electrons unequally
    Figure 2.12
    Covalent Bonding
  • 30. 29
    Ionic Bonds
    In some cases, atoms strip electrons away from their bonding partners
    Electron transfer between two atoms creates ions
    Ions
    Are atoms with more or fewer electrons than usual
    Are charged atoms
  • 31. 30
    Ions
    An anion
    Is negatively charged ions
    A cation
    Is positively charged
  • 32. 31
    Ionic Bonding
    The lone valence electron of a sodium
    atom is transferred to join the 7 valence
    electrons of a chlorine atom.
    Each resulting ion has a completed
    valence shell. An ionic bond can form
    between the oppositely charged ions.

    +
    1
    2
    Cl
    Na
    Na
    Cl
    Cl–
    Chloride ion
    (an anion)
    Na+
    Sodium on
    (a cation)
    Na
    Sodium atom
    (an uncharged
    atom)
    Cl
    Chlorine atom
    (an uncharged
    atom)
    Sodium chloride (NaCl)
    An ionic bond
    Is an attraction between anions and cations
    Figure 2.13
  • 33. 32
    Ionic Substances
    Na+
    Cl–
    Figure 2.14
    Ionic compounds
    Are often called salts, which may form crystals
  • 34. 33
    Weak Chemical Bonds
    Several types of weak chemical bonds are important in living systems
  • 35. 34
    Hydrogen Bonds
    H
    Water
    (H2O)
    O
    A hydrogen
    bond results
    from the
    attraction
    between the
    partial positive
    charge on the
    hydrogen atom
    of water and
    the partial
    negative charge
    on the nitrogen
    atom of
    ammonia.
    H
     +
     –
    Ammonia
    (NH3)
    N
    H
    H
    d+
    H
    +
    Figure 2.15
    A hydrogen bond
    Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom
     –
     +
     +
  • 36. 35
    Van der Waals Interactions
    Van der Waals interactions
    Occur when transiently positive and negative regions of molecules attract each other
  • 37. 36
    Weak Bonds
    Weak chemical bonds
    Reinforce the shapes of large molecules
    Help molecules adhere to each other
  • 38. 37
    Molecular Shape and Function
    Structure determines Function!
    The precise shape of a molecule
    Is usually very important to its function in the living cell
    Is determined by the positions of its atoms’ valence orbitals
  • 39. 38
    Orbitals & Covalent Bonds
    Hybrid-orbital model
    (with ball-and-stick
    model superimposed)
    Ball-and-stick
    model
    Space-filling
    model
    Unbonded
    Electron pair
    O
    O
    H
    H
    H
    H
    104.5°
    Water (H2O)
    H
    H
    C
    C
    H
    H
    H
    H
    (b) Molecular shape models. Three models representing molecular shape are shown for two examples; water and methane. The positions of the hybrid orbital determine the shapes of the molecules
    H
    H
    Methane (CH4)
    Figure 2.16 (b)
  • 40. 39
    Shape and Function
    Molecular shape
    Determines how biological molecules recognize and respond to one another with specificity
  • 41. 40
    Nitrogen
    Carbon
    Hydrogen
    Sulfur
    Oxygen
    Natural
    endorphin
    Morphine
    (a) Structures of endorphin and morphine. The boxed portion of the endorphin molecule (left) binds toreceptor molecules on target cells in the brain. The boxed portion of the morphine molecule is a close match.
    Natural
    endorphin
    Morphine
    Endorphin
    receptors
    Brain cell
    (b) Binding to endorphin receptors. Endorphin receptors on the surface of a brain cell recognize and can bind to both endorphin and morphine.
    Figure 2.17
  • 42. 41
    Chemical Reactions
    Chemical reactions make and break chemical bonds
    A Chemical reaction
    Is the making and breaking of chemical bonds
    Leads to changes in the composition of matter
  • 43. 42
    Chemical Reactions
    +
    2 H2O
    2 H2
    O2
    +
    Reactants
    Reaction
    Product
    Chemical reactions
    Convert reactants to products
  • 44. 43
    Chemical Reactions
    Photosynthesis
    Is an example of a chemical reaction
    Figure 2.18
  • 45. 44

×