Principles of Biology Chapter 2

Nitrogen has five electrons in its outer shell, so it can be bond with up to ___ other atoms to complete its outer shell.

3

Nitrogen has three unpaired electrons in its outer shell. The maximum number of covalent bonds that a nitrogen atom can form with other atoms while still remaining uncharged is ___.

3

An oxygen molecule contains a double bond, in which a total of ___ electrons are shared.

4

Carbon has six electrons. how many valence electrons does it have?

4

How many electrons are shared in a double bond?

4 (In a double bond, two electrons from each atom are shared.)

According to the octet rule, atoms are most stable when they have ___ electrons in their outermost shell.

8

The stability of atoms is greatest when their outer shells are filled with how many and what type of subatomic particle?

8 electrons

Which of the following best describes how a hydrogen bond forms?

A partially positive hydrogen atom and a partially negative atom in two polar molecules are attracted by electrostatic interactions.

True or False: Molecules that contain covalent bonds are rigid, inflexible structures.

False (Molecules containing covalent bonds are flexible and can change their shape when the atoms rotate around covalent bonds.)

When water ionizes, it produces what ions?

H+ and OH-

What four elements are the most common in living organisms?

Oxygen, Nitrogen, Carbon, and Hydrogen

A substance that releases hydrogen ions into a solution is called a(n):

acid

If you add more H+ ions to a solution, it becomes more:

acidic

A negatively charged particle is called a(n):

anion

A substance that absorbs hydrogen ions in a solution is called a(n):

base

Living organisms minimize changes in their internal pH using compounds called:

buffers

A positively charged particle is called a(n):

cation

The property of water molecules attracting each other is called:

cohesion

What type of bond is formed when a pair of electrons is shared between two atoms?

covalent bond

Which of the following is likely a predictor of how many covalent. bonds an atom can form? a.) the row of the periodic table that contains the atom b.) number of electrons in the innermost shell c.) the total number of electron shells d.) electron configuration in the outermost shell

d

Acid rain can ___________ the pH of water entering the roots and plants.

decrease

Because exercise produces lactic acid, it may ___________ the pH of body fluids.

decrease (An acid releases protons, thereby decreasing the pH of body fluids.)

To dissolve in water, a substance must be:

electrically attracted to water

Each specific type of atom is called a(n) ___________.

element

Sodium hydroxide is a base because when dissolved in water it binds ___________ ions that are in solution.

hydrogen

The bond between the hydrogen atom and oxygen atom of separate water molecules is a(n) __________ bond.

hydrogen

When two water molecules are near each other, a hydrogen bond will form between the __________ and __________ atoms of neighboring water molecules.

hydrogen; oxygen

An atom that has a net electric charge due to the gain or loss of electrons is called a(n) ___________.

ion

What type of bond forms between a cation and an anion?

ionic

When a cation bonds to an anion, a(n) ___________ bond forms.

ionic

Which types of chemical bonds are easily broken in water?

ionic and hydrogen bonds

What type of bond forms when a cation with a positive charge interacts with an anion carrying a negative charge?

ionic bond

A Na+ ion forms when a sodium atom ___________ an electron.

loses

How many types of atoms can be found in a single element?

only one

By mass, the most abundant element in living organisms is:

oxygen

In a water molecule, the __________ atom has a partial negative charge, and the ___________ atom has a partial positive charge.

oxygen; hydrogen

When NaCl dissolves in water, Na+ becomes surrounded by the partially negatively charged ___________ atoms of water molecules, and Cl- becomes surrounded by the partially positively charged ___________ atoms of water molecules.

oxygen; hydrogen

What are the three primarily discussed subatomic particles?

protons, neutrons, and electrons

Atoms contain three types of particles: positively charged ___________, negatively charged ___________, and uncharged ___________.

protons; electrons; neutrons

An element is defined as a(n) ___________ substance.

pure/homogenous/uniform

When methane and oxygen are converted to carbon dioxide and water, oxygen is a(n) ___________.

reactant

The kidneys can help an organism cope with changes in pH by

secreting alkaline compounds into the bloodstream and secreting acidic compounds into the bloodstream

What is the measure of attraction between molecules at the surface of a liquid?

surface tension

Electrons in an atom's outermost energy shells are called ___________ electrons.

valence

Unpaired __________ electrons enable chemical bonds to form among atoms.

valence