Transcript of Chapters 3 - 4 – The Chemical Context of Life. Matter: takes up space and has mass.
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.