+ SBI4U BIOCHEMISTRY Ms. Manning Atoms, Bonding & Molecular Polarity.
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Transcript of + SBI4U BIOCHEMISTRY Ms. Manning Atoms, Bonding & Molecular Polarity.
+SBI4U
BIOCHEMISTRY
Ms. Manning
Atoms, Bonding & Molecular Polarity
+
“. . . Everything that living things can do can be understood in terms of the jigglings and wigglings of atoms.”
Richard P. Feynman, 1963
Sperm approaching an egg
Atoms, Bonding, and Molecular Polarity
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
+MATTERMATTER
All MATTER is made up of tiny little particles called ATOMS.
Just like cells are the basic unit of life…
Atoms are the basic unit of matter.
+MATTERMATTER
Atoms are the basic unit of matter
An atom is made up of a central nucleus which contains protons and neutrons.
The nucleus is surrounded by a cloud of electrons, which are orbiting around the nucleus.
+
6
CCarbon12.011 Mass Number = protons + neutrons
The element carbon - 6th element in the periodic table
Symbol
Atomic Number = # of protons = # electrons
Bohr model of a hydrogen and oxygen atom
Shells
Nucleus
Protons
Neutrons
Subatomic Particles
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.
Why are electrons so important?• The chemical behavior 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.
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
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 electrons2 Types of Chemical Bonds
Ionic Bonds
Covalent bonds
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
Reaction between Na and Cl to form ionic sodium chloride
(salt)
Covalent Bonds – involve a sharing of a pair of valence electrons between atoms.
Figure. 1.5, p.10
Single covalent bond
Double covalent bond
Four single covalent bonds
Two single covalent bonds
Covalent bond between H2 and O to form one molecule of water
(H2O)
2 Types of Covalent Bonds
Polar Covalent Non-polar covalent
Equal sharing of electrons
Unequal sharing of electrons
All bonding types aredetermined by the atoms
ELECTRONEGATIVITY
E.g., H2
O2
E.g., H2O
Electronegativity
• the measure of the relative abilities of bonding atoms to attract electrons (Pauling Scale)Electronegativity = Stronger pull of shared electrons
The periodic table has electronegativity values.
•We can determine the nature of a bond based on ΔEN (electronegativity difference).
Electronegativity
• In a non-polar covalent bond, there is relatively 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
Calculating the Electronegative Difference
ΔEN = higher EN – lower EN
NBr3: ΔEN = 3.0 –2.8 = 0.2 (for all 3 bonds).
• Basically: a ΔEN…
below 0.5 = covalent (equal é sharing)
0.5 -1.7 = polar covalent (unequal é sharing)
above 1.7 = ionic (loss/gain of é)
Calculate electronegativity(ΔEN):
Determine the ΔEN and bond type for:HClBr2
CrOCH4
H2OKCl
The boy is not equally sharing with anyone else but rather taking all the food for
himself.
Polar Covalent Bond Analogy
Non-Polar Covalent Bond Analogy
The children are equally sharing the drink between themselves.
Ionic Bond Analogy
Parents giving up their money to keep stable when their children beg to gain
cash
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
• 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
Electronegativity and Physical Properties
Electronegativity can help to explain properties of compounds like those in the lab.
Lets look at HCl: partial charges keep molecules together.
The situation is similar in NaCl, but the attraction is even greater
(ΔEN = 2.1 vs. 0.9 for HCl.
Which would have a higher melting/boiling point?
Electronegativity and Physical Properties
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.
Solubility of Substances in WaterHydrophilic (means water-loving) compounds interact with water by dissolving in it.
E.g., Anions (chloride ions) in salt attracted to + poles of water (causes sodium cation to dissociate)
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
Choice Board Task: Atoms, Bonding and Molecular Polarity
Task:
Demonstrate your understanding of the relationship between electronegativity, bonding, and the polarity of molecules.
Success Criteria: • 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)• Prepare to present to a group of your peers• References (APA)
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 bondElectronegative
differenceReactivity or
reactive
Hydrophilic HydrophobicSoluble/Solubility
Insoluble
Isotope CompoundIntra- and inter-
molecular forces
Polar molecule
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 words )
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:
+Credits
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