BISC 104Lxg Lecture Notes - Lecture 3: Ionic Bonding, Valence Electron, Covalent Bond

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1 Feb 2017

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Valence electrons are electrons that create a covalent bond. Atoms share electrons so that each gets to complete its valence shell. Two atoms share one pair of electrons in a single covalent bond, two pairs are shared in a double covalent bond. Covalent bonds commonly involve carbon, oxygen, nitrogen, or hydrogen - elements predominant in life. Covalent bonds are more important than ionic bonds to living tissue. Most covalent bonds in human body are non polar. Ions are atoms or a group of atoms with a positive or negative electrical charge. The charge results from an uneven number of protons and electrons. An ionic bond results from the mutual attraction of oppositely charged ions. Ionic bonds are weaker than covalent bonds since they do not share electrons. When the electrons of a covalent bond are shared unequally, the bond is called polar - the resulting molecules are called polar molecules, water is an example.

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Ionic bonds are formed when two opposite charged ions (formed when atoms lose or gain electrons) encounter each other. These bonds can be viewed as âextreme polar covalent bondsâ as one atom is in total control of the otherâs electron(s). Why are ionic bonds so much weaker when they are in water?

A.	Ionic compounds such as salts are hydrophilic, so they prefer to form bonds with water molecules over other compounds.

B.	Water molecules readily form covalent bonds to charged particles and, as these bonds are stronger than ionic bonds, the ionic bonds are pulled apart.

C.	Water molecules shorten the size of covalent bonds and this weakens ionic interactions.

D.	Water molecules readily donate electrons and nullify the positively charged ions.

E.	Polar water molecules can physically interfere with the polar (positive/ negative) charged attraction between ions and thus the ionic bonds are disrupted and weakened.

Fill in the following chart with the appropriate subatomic particle and state whether each is located in the nucleus of the orbital

Particle	Charge	Location (Nucleus or Orbital)
	Positive (+)
	Negative (-)
	Neutral Charge

Fill in the following chart using the lowercase letter of the statements below. Please be aware that some letters should be used more than once because they are true for more than one type of bond.

Covalent Bonds	Ionic Bonds	Hydrogen Bonds

Electrons are transferred from one atom to another atom

Valance electrons are shared between atoms

Involves positive and negative ions

A weak bond between 2 or more polar molecules

A bond between 2 or more atoms

The type of bond used to make NaCl (table salt)

The type of bond used to make CH₄ (Methane)

What does it mean when a molecule is described as âpolar?â Be detailed in your answer.

State and explain two reasons that water molecules are essential to life because of their hydrogen bonds.

Fill in the chart with the missing information about macromolecules

Macromolecule	Dietary source	Function	Example	Defining Characteristics
Carbohydrate			Cellulose and glucose
Lipid	Fats, Oils
Protein
Nucleic Acid	Sardines, beans, spinach			Made of nucleotides (contain a base, sugar and phosphate)

greydinosaur410

2. Inductive reasoning in science:

a) is often part of the discovery process

b) proceeds from specific observations to general conclusions

c) is complementary to deductive reasoning

d) often relies on descriptive science

e) all of the above

3. A proton is a subatomic particle with:

a) a negative charge and an atomic mass of 1

b) a negative charge and a negligible mass

c) a positive charge and an atomic mass of 1

d) no charge and an atomic mass of 1

e) no charge and a negligible mass

4. Nonpolar covalent bonds are formed when:

a) electrons are shared equally by atoms

b) electrons are shared unequally by atoms

c) electrons are transferred completely from one atom to another

d) two atoms both lose electrons

e) a negative pole of one atom is attracted to a positive pole of another atom

5. Hydrogen bonds are formed when:

a) electrons are shared equally by atoms

b) electrons are shared unequally by atoms

c) electrons are transferred completely from one atom to another

d) two atoms both lose electrons

e) a negative end of one molecule is attracted to a positive end of another molecule

6. Compared with a solution of pH = 4, a solution with pH = 6 is:

a) 2 times less acidic

b) 10 times more acidic

c) 100 times more acidic

d) 10 times less acidic

e) 100 times less acidic

7. Nucleotides are formed from:

a) 3 fatty acids and a glycerol

b) 3 monosaccharides and a glycerol

c) a fatty acid, a pentose sugar, and 1 or more phosphate groups

d) a nitrogenous base, a pentose sugar, and 1 or more phosphate groups

e) an amino acid, a pentose sugar, and 1 or more phosphate groups

8. Which nucleotide base is found in RNA, but not in DNA?

a) adenine

b) cytosine

c) guanine

d) thymine

e) uracil

9. The correct sequence for the levels in the taxonomic hierarchy is:

a) domain â class â order â kingdom â phylum â genus â family â species

b) kingdom â domain â class â phylum â order â family â genus â species

c) domain â kingdom â phylum â class â order â family â genus â species

d) domain â kingdom â phylum â class â order â genus â family â species

e) phylum â kingdom â domain â order â class â genus â family â species

10. The outer (valence) shell of an atom can hold a maximum of:

a) 4 electrons

b) 6 electrons

c) 8 electrons

d) 12 electrons

e) 18 electrons

11. Which of the following is not true of lipids?

a) they are a diverse group of biological molecules

b) they are hydrophobic

c) they are less oxidized than carbohydrates

d) they are strongly polar

e) they can store more energy than carbohydrates

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BISC 104Lxg Lecture Notes - Lecture 3: Ionic Bonding, Valence Electron, Covalent Bond

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