Chapters 3 - 4 – The Chemical Context of Life

Matter: takes up space and has mass

Matter3 states

Elements

Iron

Carbon

Tellurium

Elements

Atomic structureAtom is the smallest unit of

matter (an element) that still retains properties of an element

Atomic structure

Compound2 or more elements bonded together

Atomic structure

MoleculeSmallest particle of a substance composed of at least 2 atoms

water

oxygen

a sugar

Four elements make up 96% of living matter

Atomic structure

All matter is composed of atoms

Atomic structure

Atom are composed of subatomic particles

Protons (+)

Neutrons (0)

Electrons (-)

Atomic structure

Proton(Positive charge)

Neutron(No charge)

Electron(Negative charge)

Hydrogen1 Proton1 Electron

Oxygen8 Protons8 Neutrons8 Electrons

Atomic structure

Atomic number

Atomic mass

Atomic structure

Atomic number = # of protons

Atoms with the same atomic number belong to the same element, and thus have the same inherent properties.

Atomic structure

Nucleus

ElectronsCloud of negativecharge (2 electrons)

Electrons e-

Electrons

Potential Energy

Chemical reactions

Hydrogen - 1

Oxygen - 8

Electron shell

• Electron shell is an energy level in which electrons reside

• 1st shell: maximum 2 electrons• 2nd shell: maximum 8 electrons• 3rd shell: maximum 8 electrons• 4th & 5th shells: 18 electrons• Atoms are most stable when outer shell is

filled

Electron shell diagrams

Few openings in outer shell

Chlorine

More openings in outer shell

Carbon

Neon

10Ne

Argon

18Ar

Helium

2He

Filled outer shell

• Atoms tend to react in ways that allow them to fill their outer shell– Most elements found in living systems react to

gain 8 electrons in their outer shells

Octet rule

No open slots – very stable

Open slots – reactive

Electrons

Potential Energy

Chemical reactions

Third energy level (shell)

Second energy level (shell)

First energy level (shell)

Atomicnucleus

Energyabsorbed

Energylost

Electrons and energy

Electrons and energy

Potential energy

Potential energy released

Energy put to work

Electrons and energy

Electrons

Potential Energy

Chemical reactions

Chemical Bonds

• A. Covalent bond

• B. Ionic bond

• C. weak chemical bonds

Chemical Bonds

Hydrogen atoms (2 H)

Hydrogenmolecule (H2)

Covalent Bond

Covalent Bond

Hydrogen

Oxygen (O2)

Water (H2O)

Methane (CH4)

Covalent Bond

• Some atoms can form more than one bond.– Hydrogen: one bond– Oxygen: two bonds– Nitrogen: three bonds– Carbon: four bonds

Covalent Bonds

Polar covalent bondsbond in which electrons are

shared unequally.

Na+

Cl–

Ionic Bonds

Na

Sodium atom(an uncharged

atom)

Cl

Chlorine atom(an uncharged

atom)

Na+

Sodium ion(a cation)

Cl–

Chlorine ion(an anion)

Ions+ -

Na+

Sodium ion(a cation)

Cl–

Chlorine ion(an anion)

Ions+ -

Ion: A atom carrying a electric charge which is formed either by gaining or losing electrons.

Na+

Sodium ion(a cation)

Cl–

Chlorine ion(an anion)

Sodium chloride (NaCl)

Ionic bond

Na

Sodium atom(an uncharged

atom)

Cl

Chlorine atom(an uncharged

atom)

Na+

Sodium ion(a cation)

Cl–

Chlorine ion(an anion)

Sodium chloride (NaCl)

Ionic bonding

Weak chemical bonds

• Hydrogen bonds

• Van der Waals

Weak chemical bonds

–

+

OxygenHydrogen

Hydrogen

Bohr model

8+8n

+

+

–

+

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Hydrogen bonds

Unstable hydrogenbonds

Watermolecules

Liquid water

Hydrogen bonding

–

Water(H2O)

Ammonia(NH3)

Hydrogen bond

+

+

–

+

+

+

Hydrogen bonding

Water (H2O)

Methane (CH4)

104.5°

Molecules have shape

Naturalendorphin

Morphine

Structures of endorphin and morphine

Shape and Function

Naturalendorphin

Morphine

Brain cell

Endorphinreceptors

Shape and Function

Reactants Reaction Products

2 H2OO22 H2

Chemical Reactions

Energy and Chemical Reactions