BIO110 Chapter 2: The Chemistry of Life

2.1 What is the basic structure of all atoms?

A very dense nucleus at its core that hosts 2 subatomic particles (protons and neutrons) with a surrounding cloud consisting of another subatomic particle (electrons).

2.1 What one element is an exception to the basic atomic structure?

Hydrogen; it has no neutrons.

2.1 How are atoms characterized?

By its atomic number (proton number) or mass number (the number of protons and neutrons in the nucleus).

2.1 Why are electrons associated with energy?

They have potential energy because it takes energy to oppose their natural attraction to the nucleus.

2.1 What are electron shells?

The layers of energy surrounding the nucleus.

2.1 What are orbitals?

The space within an electron shell where electrons are most likely to be found.

2.1 Why do atoms with incomplete electron orbitals tend to be more reactive?

Because atoms will lose, gain, or share electrons in order to fill completely their outermost electron shell.

2.1 When electrons move to a lower energy level, do they move closer or farther from the nucleus?

Closer.

2.1 When electrons move to a lower energy level, do they absorb or release energy?

Release.

2.1 When electrons move to a higher energy level, do they move closer or farther from the nucleus?

Farther.

2.1 When electrons move to a higher energy level, do they absorb or release energy?

Absorb.

2.1 Why do electrons absorb energy when they move to farther energy levels?

Because moving electrons farther out from the nucleus requires energy to overcome the attraction to the positive charge of the nucleus.

2.2 What are ions?

Atoms that have gained or lost one or more electrons, in other words, the number of electrons doesn’t equal the number of protons; they carry an electrical charge.

2.2 What are isotopes?

Atoms that have the same amount of protons but a different number of neutrons.

2.3 What is a chemical bond?

The energy holding atoms together, of which there are 3 main types.

2.3 What are the 3 main types of chemical bonds?

1) Ionic 2) Covalent 3) Hydrogen.

2.3 What are ionic bonds?

A chemical bond formed between ions as a result of opposite electrical charges.

2.3 What are covalent bonds?

A chemical bond formed by the sharing of one or more pairs of electrons.

2.3 What are some characteristics of covalent bonds?

They are stronger than ionic bonds and may be polar or nonpolar.

2.3 What are polar covalent bonds?

Covalent bonds where one nucleus attracts the shared electrons more than the other; it is caused by the atom’s electronegativity and results in partial charges in the molecule, making it polar.

2.3 What are hydrogen bonds?

A molecular bond formed by the attraction of the partial positive charge of a hydrogen atom of a water molecule to the partial negative charge of the oxygen atom of another.

2.4 Why is water highly polar?

The oxygen in water attracts shared electrons more strongly than the hydrogen.

2.4 What are hydrophilic molecules?

Molecules that are attracted to water and easily dissolve in it.

2.4 What are hydrophobic molecules?

Molecules that are repelled by water and don’t dissolve in it.

2.4 Are hydrophobic molecules polar or nonpolar?

Nonpolar, and don’t form hydrogen bonds.

2.4 What is cohesion?

The molecular attraction between the surfaces of like bodies in contact, such as that between water molecules.

2.4 What is an example of cohesion?

Surface tension.

2.4 What is adhesion?

The molecular attraction between the surfaces of different bodies in contact.

2.4 What is an example of adhesion?

Capillary action.

2.4 What is heat storage as a property of water?

Water temperature changes slowly and can hold temperature well.

2.4 Why does it take so long for water to become warm?

It takes a large amount of energy to disrupt the organization of liquid water due to hydrogen bonding.

2.4 What is ice formation as a property of water?

Water becomes less dense as it freezes because hydrogen bonds stabilize and hold water molecules further apart.

2.4 Why do hydrogen bonds stabilize when forming ice?

Few hydrogen bonds break at low temperatures.

2.4 What is the high heat of vaporization as a property of water?

Water requires a lot of energy to vaporize due to its hydrogen bonds.

2.4 Why can water vaporize?

At high temperatures, hydrogen bonds can be broken.

2.5 What happens when the covalent bonds within a water molecule break spontaneously?

The proton (hydrogen atom nucleus) dissociates and its charge is no longer counterbalanced, resulting in a positively charged hydrogen ion (H⁺) and a negatively charged hydroxide ion (OH^-).

2.5 What is the process of spontaneous ion formation called?

Ionization.

2.5 What is pH?

The measure of hydrogen ions in a solution.

2.5 What is the pH of pure water?

7.

2.5 Why is the pH of water what it is?

There are an equal amounts of hydrogen ions relative to hydroxide ions.

2.5 What is an acid?

Any substance that dissociates in water and increases the amount of hydrogen ions; pH = below 7.

2.5 What is a base?

Any substance that combines with hydrogen ions when dissolved in water; pH = above 7.

2.5 What is a buffer?

A chemical substance that takes up or releases hydrogen ions.

2.5 Do buffers remove the acid/base affecting pH?

No, they just minimize their affect on it.

2.5 What do most buffers consist of?

A pair of substances: one acid & one base.