Chapter 2

What are the fundamental components of living matter.

nucleic acids, proteins, carbohydrates, and lipids

At its most fundamental level, life is made up of?

matter

The four elements common to all living organisms are

oxygen (O), carbon (C), hydrogen (H), and nitrogen (N)

Atoms contain

protons, electrons, and neutrons, among other subatomic particles.

The most common isotope of hydrogen (H) is the only exception and is made of

one proton and one electron with no neutrons.

similar in mass, protons and neutrons differ in their?

electric charge.

the number of neutrons in an atom contributes significantly to its

mass, but not to its charge.

each electron has a

negative charge equal to the proton's positive charge

Atoms that vary in the number of neutrons found in their nuclei are called

isotopes

If xenon has an atomic number of 54 and a mass number of 108, how many neutrons does it have?

54

Potassium has an atomic number of 19. What is its electron configuration?

shells 1, 2 and 3 are full and shell 4 has one electron

Which type of bond represents a weak chemical bond?

hydrogen bond

Which of the following statements is not true?


1. Water is polar.
2. Water stabilizes temperature.
3. Water is essential for life.
4. Water is the most abundant molecule in the Earth’s atmosphere.

Water is the most abundant molecule in the Earth’s atmosphere.

When acids are added to a solution, the pH should?

decrease

most of the atom's volume—greater than 99 percent—is

empty space

electrons that surround all atoms are negatively charged and negative charges

repel each other

The number of protons determines an element’s

atomic number

the number of protons and neutrons determine an element’s

mass number

We find functional groups

along the

“carbon backbone” of macromolecules

functional group include:

hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl

functional groups play an important role in forming molecules like

DNA, proteins, carbohydrates, and lipids.

We usually classify functional groups as hydrophobic or hydrophilic depending on their

charge or polarity characteristics

to easily calculate how many neutrons an element has you simply

subtract the number of protons from the mass number

Some elements—such as carbon, potassium, and uranium—have

naturally occurring isotopes

Radioactive decay

describes the energy loss that occurs when an unstable atom’s nucleus releases radiation

the periodic table also displays the

element’s atomic mass

in all electrically neutral atoms, the number of

electrons is the same as the number of protons

Niels Bohr (1885–1962) developed

an early model of the atom

Bohr model shows the

atom as a central nucleus containing protons and neutrons

Electrons fill orbitals in a consistent order:

they first fill the orbitals closest to the nucleus, then they continue to fill orbitals of increasing energy further from the nucleus

The electrons of the outermost energy level determine the

atom's energetic stability and its tendency to form chemical bonds with other atoms to form molecules.

An atom may

give, take, or share electrons with another atom to achieve a full valence shell,

Scientists call the area where an electron is most likely to be found its

orbital

Moving away from the nucleus, the

number of electrons and orbitals in the energy levels increases

The closest orbital to the nucleus, the

1s orbital, can hold up to two electrons

All elements are most stable when their

outermost shell is filled with electron

When two or more atoms chemically bond with each other, the

resultant chemical structure is a molecule

the law of conservation of matter

the number of atoms before and after a chemical reaction should be equal, such that no atoms are, under normal circumstances, created or destroyed

In reversible reactions

reactants turn into products

We designate anions by their elemental name and change the ending to

\-ide

Another way to satisfy the octet rule is by

sharing electrons between atoms

We commonly find covalent bonds in carbon-based organic molecules, such as

our DNA and proteins

The more covalent bonds between two atoms, the

stronger their connection

Covalent bonds bind the

hydrogen and oxygen atoms that combine to form water molecules

There are two types of covalent bonds:

polar and nonpolar

the unequal electron distribution between the atoms of different elements

a slightly positive (*δ*+) or slightly negative (*δ*–) charge develops.

Ionic and covalent bonds between elements require

energy to break

the hydrogen in that bond has a slightly positive charge because

hydrogen’s electron is pulled more strongly toward the other element and away from the hydrogen

Water is

one of the more abundant molecules and the one most critical to life on Earth

Special properties of water are its

high heat capacity and heat of vaporization, its ability to dissolve polar molecules, its cohesive and adhesive properties, and its dissociation into ions that leads to generating pH

water's polarity creates a

slightly positive charge on hydrogen and a slightly negative charge on oxygen

As a result of water’s polarity

each water molecule attracts other water molecules

In liquid water

hydrogen bonds constantly form and break as the water molecules slide past each other

Water’s lower density in its solid form is due to

the way hydrogen bonds orient as they freeze: the water molecules push farther apart compared to liquid water

As the water evaporates, energy is

taken up by the process, cooling the environment where the evaporation is taking place.

In many living organisms, including in humans, the evaporation of sweat, which is 90 percent water, allows the organism

to cool so that it can maintain homeostasis of body temperature

Since water is a polar molecule with slightly positive and slightly negative charges

ions and polar molecules can readily dissolve in it

Dissociation occurs when

atoms or groups of atoms break off from molecules and form ions

Cohesion allows for

surface tension

Cohesive and adhesive forces are important for

transporting water from the roots to the leaves in plants

the pH test measures

hydrogen ions' concentration in a given solution

One mole represents the

atomic weight of a substance, expressed in grams

high concentrations of hydrogen ions yield

a low pH number

low levels of hydrogen ions result in

a high pH

hydrocarbons may exist as

linear carbon chains, carbon rings, or combinations of both

individual carbon-to-carbon bonds may be

single, double, or triple covalent bonds, and each type of bond affects the molecule's geometry in a specific way

Successive bonds between carbon atoms form

hydrocarbon chains

a molecule's different geometries of single, double, and triple covalent bonds alter the

overall molecule's geometry

single bonds allow rotation along the

bond's axis

double bonds lead to a planar configuration and triple bonds to a

linear one

different atom arrangement within the molecules leads to

differences in their chemical properties

When the carbons are bound on the same side of the double bond, this is

the *cis* configuration

If they are on opposite sides of the double bond, it is

a *trans* configuration

**acid**

molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution

**adhesion**

attraction between water molecules and other molecules

**aliphatic hydrocarbon**

hydrocarbon consisting of a linear chain of carbon atoms

**anion**

negative ion that is formed by an atom gaining one or more electrons

**aromatic hydrocarbon**

hydrocarbon consisting of closed rings of carbon atoms

**atom**

the smallest unit of matter that retains all of the chemical properties of an element

**atomic mass**

calculated mean of the mass number for an element’s isotopes

**atomic number**

total number of protons in an atom

**balanced chemical equation**

statement of a chemical reaction with the number of each type of atom equalized for both the products and reactants

**base**

molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the hydrogen ions' concentration in a solution

**buffer**

substance that resists a change in pH by absorbing or releasing hydrogen or hydroxide ions

**calorie**

amount of heat required to change the temperature of one gram of water by one degree Celsius

**capillary action**

occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the tubes' sides

**cation**

positive ion that is formed by an atom losing one or more electrons

**chemical bond**

interaction between two or more of the same or different atoms that results in forming molecules

**chemical reaction**

process leading to rearranging atoms in molecules

**chemical reactivity**

the ability to combine and to chemically bond with each other

**cohesion**

intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension

**compound**

substance composed of molecules consisting of atoms of at least two different elements

**covalent bond**

type of strong bond formed between two atoms of the same or different elements; forms when electrons are shared between atoms

**dissociation**

release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H+ and OH-

**electrolyte**

ion necessary for nerve impulse conduction, muscle contractions, and water balance

**electron**

negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of –1 unit

**electron configuration**

arrangement of electrons in an atom’s electron shell (for example, 1s22s22p6)

**electron orbital**

how electrons are spatially distributed surrounding the nucleus; the area where we are most likely to find an electron

**electron transfer**

movement of electrons from one element to another; important in creating ionic bonds

**electronegativity**

ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms