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+SBI4U
BIOCHEMISTRYAtoms, Bonding & Molecular Polarity
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+Sperm approaching an egg
“. . . Everything that living things can do can be understood in terms of the jigglings and wigglings of atoms.”
Richard P. Feynman, 1963
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Atoms, Bonding, and Molecular Polarity
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6 types of atoms make up 99% of all living organisms
Element Symbol Atomic #% of human body weight
Oxygen O 8 65.0
Carbon C 6 18.5
Hydrogen H 1 9.5
Nitrogen N 7 3.3
Calcium Ca 20 1.5
Phosphorus P 15 1.0
Potassium K 19 0.4
Sulfur S 16 0.3
Sodium Na 11 0.2
Chlorine Cl 17 0.2
Magnesium Mg 12 0.1
Naturally Occurring Elements in the Human Body
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Atoms and Elements
Matter is any substance in the universe that has mass and occupies space
All matter is composed of extremely small particles called atoms, which is the smallest unit of any given element.
Every atom has the same basic structure:Subatomic Particles
Core nucleus of protons and neutronsOrbiting cloud of electrons
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+
6
CCarbon12.011 Mass Number = protons + neutrons
The element carbon - 6th element in the periodic table
Symbol
Atomic Number = # of protons = # electrons
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Bohr model of a hydrogen and oxygen atom
Shells
Nucleus
Protons
Neutrons
Subatomic Particles
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Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14
6 electrons6 protons6 neutrons
6 electrons6 protons8 neutrons
6 electrons6 protons7 neutrons
Isotopes are atoms of the same element that vary in the number of neutrons.
Because they have the same number of electrons, all isotopes of an element have the same chemical properties.
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Why are electrons so important?• The chemical behaviour of an atom is determined by its electron configuration – that is, the distribution of electrons in the atom’s electron shells.
•The chemical behaviour of an atom depends mostly on the number of electrons in its outermost shell. (= valence electron/shell)
•All atoms with incomplete valence shells are chemically reactive.
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Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
C would like to N would like toO would like toH would like to
Gain 4 electronsGain 3 electronsGain 2 electronsGain 1 electron
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Atoms bond to form compounds
• Compounds are made up of at least 2 different kinds of atoms (e.g., H2O)
• Bonds are formed by the sharing or transfer of electrons
2 Types of Chemical Bonds
Ionic Bonds
Covalent bonds
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Ionic Bonds – occur when one atom donates or gives up one or more electrons
Ionic Compound ( Na+Cl-) Salt crystals
Opposite charges
attract to form ionic
bonds
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Covalent Bonds – involve a sharing of a pair of valence electrons between atoms.
Figure. 1.5, p.10
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Single covalent bond
Double covalent bond
Four single covalent bonds
Two single covalent bonds
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2 Types of Covalent Bonds
Polar Covalent Non-polar covalent
Equal sharing of electrons
Unequal sharing of electrons
Determined by the atoms
ELECTRONEGATIVITY
E.g., H2
O2
E.g., H2O
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Electronegativity
• the measure of the relative abilities of bonding atoms to attract electrons (Pauling Scale)
• In a non-polar covalent bond, there is no electronegative difference. Electrons are shared equally. E.g., O2 oxygen atoms have the same
elecronegativity
• In a polar covalent bond, there is an electronegative difference. Electrons are shared unequally. E.g., H2O oxygen atom is more
electronegative than the hydrogen atoms
Electronegativity = Stronger pull of shared electrons
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Water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.
Shared electrons spend more time near the the oxygen nucleus
As a result, the oxygen atom gains a slightly negative charge and the hydrogen atoms become slightly positive
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• Polar Molecules (like water) have an unequal distribution of charge.
• Since water is polar, it can attract other water molecules.
• The attraction betweenwater molecules are called hydrogen bonds.
Hydrogen bonds are weak forces between molecules
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Solubility of Substances in Water
Cl-
Water
Cl-
Na+
Water
Na+
Due to water’s polarity, it is a great solvent. A solvent is a substance in which a solute dissolves. A solute is what is being dissolved. What is happening in the example below?
Water is great at dissolving both ionic (+,-) compounds and polar (partialpositively, partial negatively charged molecules) molecules.
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Solubility of Substances in Water
Hydrophilic (means water-loving) compounds interact with water by dissolving in it.
E.g., Anions (chloride ions) in salt attracted to + poles of water
Hydrophobic (means water-hating) compounds do not interact with water because they cannot form hydrogen bonds
E.g., Non-polar compounds are insoluble in water
Oil – non-polar compound of carbon and hydrogen
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For Friday:
• Incorporate, at least, the following terms in your product:
• Include examples and/or diagrams where appropriate.
• Ensure that your product is self-explanatory (provide explanations for visual elements where appropriate)
Electron(s) Atom(s) Protons Neutrons
MoleculesValence shell or
valence electron
Covalent bond Ionic bond
Cation AnionElectronegativit
yNon-polar
covalent bond
Polar covalent bond
Hydrogen bond Polar moleculeReactivity or
reactive
Hydrophilic Hydrophobic Soluble Insoluble
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Choice Board
LOGICAL-MATHEMATICAL
Create a flow chart, or matrix
Be sure to study the criteria carefully before you select and as you
proceed.
BODILY-KINESTHETICConstruct a model, or
representation (include a written explanation)
VISUAL SPATIALDesign a graphic
organizer (e.g., concept map with
connecting phrases between )
WILD CARD
INTERPERSONAL Write a short story that incorporates characters
and a plot.
MUSICAL-RHYTHMICCreate a rap, jingle or
song
INTERPERSONAL Develop a role play, an oral presentation, or a
YouTube video
VERBAL LINGUISTICCreate a poem, poster or print advertisement
Choose a mode to express your understanding: