1. SBI4U BIOCHEMISTRY
Atoms, Bonding &
Molecular Polarity

2. Brainstorm
What is a cell?
What is a cell made of?

3. Think back… What is an atom? What is a compound?
Bonus question: What is the difference between a molecule and a compound?

4. Atoms, Bonding, and Molecular Polarity

5. 6 types of atoms make up 99% of all living organisms
Naturally Occurring Elements in the Human Body
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
Magnesium Mg 12
0.1

6. 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 neutrons
Orbiting cloud of electrons

7. C 6 Carbon 12.011 Atomic Number = # of protons = # electrons Symbol
The element carbon - 6th element in the periodic table 6 C
Carbon
12.011
Atomic Number = # of protons
= # electrons
Symbol
Mass Number = protons + neutrons

8. Bohr model of a hydrogen and oxygen atom
Protons
Nucleus
Neutrons
Shells
Subatomic Particles

9. Isotopes are atoms of the same element that vary in the number of neutrons.
Nonradioactive carbon-12
Nonradioactive carbon-13
Radioactive carbon-14
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
6 electrons
6 protons
8 neutrons
Because they have the same number of protons, all isotopes of an element have the same chemical properties.

10. Why are electrons 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 largely on the number of electrons in its outermost shell. (= valence electron/shell)
All atoms with incomplete valence shells are chemically reactive.

11. C would like to N would like to O would like to H would like to
Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
C would like to
N would like to
O would like to
H would like to
Gain/lose 4 electrons
Gain 3 electrons
Gain 2 electrons
Gain 1 electron

12. Chemical Bonds

13. 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
Ionic Bonds
2 Types of
Chemical Bonds
Covalent bonds

14. Recall…
What is the difference between an ionic bond and a covalent bond?

15. Opposite charges attract to form ionic bonds
Ionic Bonds – occur when one atom donates or gives up one or more electrons
Opposite charges attract to form ionic bonds
Salt crystals
Ionic Compound ( Na+Cl-)

16. Covalent Bonds – involve a sharing of a pair of valence electrons between atoms.
Figure. 1.5, p.10

17. Single covalent bond
Double covalent bond
Four single covalent bonds
Two single covalent bonds

18. 2 Types of Covalent Bonds
Polar Covalent
Non-polar covalent
Unequal sharing
of electrons
Equal sharing
of electrons
E.g., H2 O2
E.g., H2O
Determined by the atoms
ELECTRONEGATIVITY

19. 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

20. Polar Covalent Analogy
The boy is not equally sharing with anyone else but rather taking all the food for himself.

21. The children are equally sharing the drink between themselves.
Non-Polar Covalent Analogy
The children are equally sharing the drink between themselves.

22. 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
Water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

23. Polar Molecules (like water) have an unequal distribution of charge.
Since water is polar,
it can attract other
water molecules.
The attraction between
water molecules are
called hydrogen bonds.
Hydrogen bonds are weak forces between molecules

24. Solubility of Substances in Water
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?
Cl-
Water
Na+
Na+
Water is great at dissolving both ionic (+,-) compounds and polar (partial positively, partial negatively charged molecules) molecules.

25. Solubility of Substances in Water:
LIKE DISSOLVES LIKE!
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

26. Mini-Task: Atoms, Bonding and Molecular Polarity
Homework Task:
Demonstrate your understanding of the relationship between electronegativity, bonding, and the polarity of molecules.
*Refer to pages 9-16 in your text as well as these notes to help you conceptualize this information!

27. 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)
Electron(s)
Atom(s)
Protons
Neutrons
Molecules
Valence shell or valence electron
Covalent bond
Ionic bond
Cation
Anion
Electronegativity
Non-polar covalent bond
Polar covalent bond
Hydrogen bond
Polar molecule
Reactivity or reactive
Hydrophilic
Hydrophobic
Soluble
Insoluble

28. LOGICAL-MATHEMATICAL
Choice Board
Choose a mode to express your understanding:
* me a copy of your product by Wed. October 2
LOGICAL-MATHEMATICAL
Create a flow chart, or matrix
Be sure to study the criteria carefully before you select and as you proceed.
BODILY-KINESTHETIC
Construct a model, or representation (include a written explanation)
VISUAL SPATIAL
Design 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-RHYTHMIC
Create a rap, jingle or song
Develop a role play, an oral presentation, or a YouTube video
VERBAL LINGUISTIC
Create a poem, poster or print advertisement