Chapter 2 Objectives

Question 1

atomic number

Answer 1

The number of protons in an element

Question 2

atomic mass

Answer 2

The sum of the number of protons and neutrons in the atom.

Question 3

isotope

Answer 3

An element that has the same number of protons but a different number of neutrons

Question 4

radioactive isotope

Answer 4

The ratio of protons to isotopes can cause for an unstable nucleus that is not as firmly held together due to the different number of protons.

Question 5

electron shell

Answer 5

The orbitals of the atom where the electrons are located in different levels numbered 1, 2, 3 and so on to indicate their proximity to the nucleus. Each shell can contain a specific number of electrons

Question 6

Valence shell

Answer 6

the outermost shell of the atom

Question 7

Valence electron

Answer 7

the electron(s) found in the outermost shell

Question 8

Valence

Answer 8

The number of unpaired electrons in the outermost electron shell of an atom; determines how many covalent bonds the atom can form.

Question 9

covalent bond

Answer 9

the bonds formed when atoms share two valence electrons. Covalent bonds can be polar or nonpolar according to the electronegativity of the elements involved and how much they evenly share the electrons.

Question 10

organic compounds

Answer 10

Organic compounds are covalent compounds that contain carbon and hydrogen. They might also contain smaller amounts of other elements such as sulfur, phosphorous, or any of the halogens.

Question 11

ionic bond

Answer 11

One element loses an electron while another gains an electron, causing ions (charged atoms) that then bond to each other due to their opposite charges.
Cation is positively charged
anion is negatively charged

Question 12

hydrogen bond

Answer 12

Bonds that form because opposite, partial electric charges on polar molecules attract. (dipole dipole interaction)

Question 13

Why is a hydrogen bond weaker than a covalent bond?

Answer 13

The dipole dipole interaction of partially charged molecules is not as strong as the interaction

Question 14

Van der Waals interactions

Answer 14

A weak electrical attraction between two hydrophobic side chains. Often contributes to tertiary structure in proteins.

Question 15

mole

Answer 15

The amount of a substance that contains 6.022 x10^23 of an element. It also equals the molecular weight of a compound in grams.

Question 16

molecular weight

Answer 16

The molecular weight is the sum of the mass numbers of all the atoms in the molecule.

Question 17

molarity

Answer 17

The number of moles of the substance present per liter of solution.

Question 18

energy

Answer 18

capacity to do work

Question 19

What are the two major categories of energy?

Answer 19

Kinetic (constant motion) and potential energy (stored energy)

Question 20

What type of energies do molecules have?

Answer 20

Molecules have kinetic energy because they are constantly in motion. The kinetic energy of molecular motion is called thermal energy.

Question 21

entropy (S)

Answer 21

the amount of disorder in a group of molecules

When products of a chemical reaction are less ordered than the reactant molecules, entropy increases and ΔS is positive. Spontaneous reactions tend to increase entropy.

generally, physical and chemical processes proceed in the direction that results in lower potential energy and increased disorder

Question 22

ΔG

Answer 22

Gibbs free-energy change - used to determine whether a reaction is spontaneous by assessing the combined contributions of changes in heat and disorder

ΔG = ΔH - TΔS

When ΔG is less than zero, chemical reactions are spontaneous

Question 23

exergonic

Answer 23

when chemical reactions are spontaneous and ΔG is less than zero

Question 24

endergonic

Answer 24

Non-spontaneous chemical reactions and ΔG is greater than zero.