Chapter 2: The Chemistry of Life

Fill-in-the-blank flashcards covering core concepts from atomic structure, isotopes, bonding, and water chemistry (Chapter 2).

All matter is composed of __.

atoms

Electrons have a __ mass.

negligible

Electrons have a __ charge.

negative

The atomic nucleus contains protons and __.

neutrons

Neutrons have a __ charge.

no charge

In a neutral atom, the number of protons equals the number of __.

electrons

The number of protons identifies an element and is called its __.

atomic number

The total number of protons and neutrons gives the element's __.

mass number

Isotopes are forms of an element with different numbers of __.

neutrons

Mass number is the sum of protons and __.

neutrons

Radioisotopes give off energy in the form of __ radiation.

alpha, beta, and gamma

A molecule is a stable association of __.

atoms

The number of electrons in an atom determines how it will __ with other atoms.

react

The first shell (innermost) holds __ electrons.

2

The second shell holds up to __ electrons.

8

Additional shells each hold up to __ electrons.

8

The outermost shell is the __ shell.

valence

Reactive atoms can share electrons or __ electrons.

lose

The Octet rule states that atoms tend to form stable molecules by achieving full __ shells.

valence

A chemical bond is an attractive force that links atoms together to form __.

molecules

A covalent bond involves atoms sharing one or more pairs of electrons so that the outer shells are filled. Each atom contributes one member of each electron __.

pair

A pure substance made up of two or more different elements bonded together in a fixed ratio is a __.

compound

In water, two hydrogen atoms are bonded to one __ atom.

oxygen

The molecular weight of a compound is the sum of the __ weights of all atoms in the molecule.

atomic

Hydrogen's usual covalent bond count is __.

1

Oxygen's usual covalent bond count is __.

2

Sulfur's usual covalent bond count is __.

2

Nitrogen's usual covalent bond count is __.

3

Carbon's usual covalent bond count is __.

4

Phosphorus's usual covalent bond count is __.

5

Single covalent bonds share __ pair(s) of electrons.

one

Double covalent bonds share __ pairs of electrons.

two

Triple covalent bonds share __ pairs of electrons.

three

Bond energies are higher in __ covalent bonds.

multiple

Sharing of electrons in a covalent bond is not always __.

equal

Electronegativity is the attractive force that a nucleus exerts on __.

electrons

Electronegativity depends on the number of __ and the distance between the nucleus and electrons.

protons

Nonpolar covalent bonds occur when electrons are shared __.

equally

Polar covalent bonds form when one atom has greater __ than the other.

electronegativity

Water is a classic example of a __ molecule.

polar covalent

Ionic bonds are formed by the electrical attraction between positive and negative __.

ions

Cations are __.

positive

Anions are __.

negative

Hydrogen bonds are an attraction between the hydrogen end of one molecule and the __ end of another molecule.

electronegative

Molecules that form hydrogen bonds with water are __.

hydrophilic

Nonpolar molecules such as hydrocarbons are __.

hydrophobic

Van der Waals forces are attractions between nonpolar molecules that are __.

close

Chemical reactions occur when atoms collide with enough energy to __ or change their bonding partners.

combine

The products of propane combustion are __ and water.

carbon dioxide

In redox reactions, the oxidizing agent gains electrons and becomes __.

reduced

The reducing agent loses electrons and becomes __.

oxidized

Ice floats because water forms a rigid crystalline structure due to __ bonds.

hydrogen

To melt ice, a lot of energy is required to break __ bonds.

hydrogen

Water has a high heat of __.

vaporization

Cohesion is the attraction between water molecules that causes them to __.

stick together

Adhesion is the attraction of water molecules to other molecules of a __ type.

different

The substance dissolved in a solution is the __.

solute

The liquid that dissolves the solute is the __.

solvent

Acids release __ ions in water.

hydrogen

Bases accept __ ions.

H+

pH is the negative log of the __ concentration of free H ions in the solution.

molar

Buffers help maintain constant __.

pH

Living organisms maintain constant internal conditions, a state known as __.

homeostasis