chemistry of life
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Chemistry of Life. Biology Chapter 2. Elements. Substances that cannot be broken down chemically into simpler kinds of matter More than 100 types Organized on the periodic table of elements. Elements of Life. Approximately 27 are essential to life - PowerPoint PPT PresentationTRANSCRIPT
Chemistry of Life
Biology Chapter 2
Elements
• Substances that cannot be broken down chemically into simpler kinds of matter
• More than 100 types• Organized on the
periodic table of elements
Elements of Life
• Approximately 27 are essential to life• 90% of mass of living things are O, C, H, N• Elements of Life: CHONPS• Remember the Elephants in the Element
Song?
Atom
• Smallest unit of an element that retains all the properties of that element
Nucleus
• Central region of an atom• Contains the bulk of the mass of the atom• Consists of protons and neutrons
Proton
• Positively charged particle• Located in Nucleus• Mass approximately 1 AMU
http://www.fas.org/nuke/guide/usa/doctrine/dod/fm8-9/fig2-I.gifhttp://images.thecarconnection.com/med/proton-logo_100378711_m.jpg
Neutron
• Neutral charged particle, No Charge• Located in Nucleus• Mass approximately 1 AMU
http://www.chem4kids.com/files/art/atom_struct1.gif
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http://www.chem4kids.com/files/art/atom_neutron1.gif
Electron
• Negatively charged particle• Orbits the nucleus in the electron cloud• Mass practically zero
Orbitals
• Electrons orbit in specific regions called orbitals-
• 3D space higher probability location of orbital• Each orbital is associated with an energy level• Electrons in orbitals further from the nucleus
have more energy
Electron Orbitals & Energy Levels
• Each orbital can hold 2 electrons• Each energy level consists of different #s of
orbitals
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Build an Atom
Atomic Number
• Number of protons in an atom • Determines type of element• Elements are organized by atomic number on
the periodic table• Atomic Number for Carbon is 6
Mass Number
• Total number of Protons + Neutrons
• Protons have mass of 1 amu
• Neutrons have mass of 1 amu
• Mass Number – Atomic Number = # of neutrons
http://www.sawyerscience.com/assets/images/units/unit_2/atomic_Mass.jpg
Mass Number
http://chemwiki.ucdavis.edu/@api/deki/files/8320/He_Atom.png
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Compounds
• Made of atoms of two or more elements in fixed proportions
• Chemical formula shows kinds and proportions of atoms
• H2O -
• C6H12O6 –
• CO2- • CO - • O2- Compound?
Molecule
• Simplest part of a substance that retains all properties of that substance
• Can exist in a free state• Can be very large- carbohydrates, lipids, proteins, nucleic
acids (macromolecules)• H2O -
• C6H12O6 –
• CO2- • CO - • O2-
Chemical Bonds
• Attractive forces that hold atoms together• Covalent Bonds• Ionic Bonds• Hydrogen Bonds
Stable Atom = Highest energy level filled
Valence Electrons
• Number of electrons in the highest energy level for that atom
• Atoms are more stable when outer energy level is full (2 or 8 electrons depending on element)
Dot Diagrams
• Show the valence electrons on an atom• Hydrogen and helium only hold up to 2
valence electrons• Other elements (that we will look at) hold up
to 8 valence electrons
http://webgenchem.com/lewishcn.gifhttp://legacy.jyi.org/volumes/volume3/issue1/features/peterson.html
Covalent Bond
• Two atoms share one or more pairs of electrons
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/chemistry/chemistr.htm
Ion
• Some atoms only need to gain or lose 1 or 2 electrons to be stable
• Ions- Forms of an atom that have gained or lost electrons
• Fills the outer shell of electrons• If electrons are gained, Ion is NEGATIVE
(ANION)• If electrons are lost, Ion is POSITIVE (CATION)
Ion Example
• Sodium and Chlorine
Ionic Bonding
• Atoms form ions and become positive or negative
• Opposite charges attract