Chapter 2: The Chemical Context of Life

Question 1

a substance consisting of two or more different elements combined in a fixed ratio

Answer 1

compound

Question 2

those required by an organism in only minute quantities

Answer 2

Trace elements

Question 3

dense core

Answer 3

atomic nucleus

Question 4

• written as a subscript to the left of the symbol for the element
• tells us the number of protons and also the number of electrons in an electrically neutral atom

Answer 4

atomic number

Question 5

sum of protons plus neutrons in the nucleus of an atom

Answer 5

mass number

Question 6

we can determine the number of neutrons by subtracting the _______ from the _______

Answer 6

atomic number ;mass number

Question 7

different atomic forms

Answer 7

isotopes

Question 8

the nucleus decays spontaneously, giving off particles and energy

Answer 8

radioactive isotope

Question 9

capacity to cause change

Answer 9

Energy

Question 10

energy that matter possesses because of its location or structure

Answer 10

potential energy

Question 11

different states of potential energy that electrons have in an atom

Answer 11

energy levels

Question 12

An electrons energy level is correlated with its average distance from the nucleus; these average distances are represented symbolically by ___________

Answer 12

electron shells

Question 13

outer electrons

Answer 13

valence electrons

Question 14

outermost electron shell

Answer 14

valence shell

Question 15

three dimensional space where an electron is found 90% of the time

Answer 15

orbital

Question 16

a subtance that cannot be broken down to other substances by chemical reactions

Answer 16

element

Question 17

sharing of a pair of valence electrons by two atoms

Answer 17

covalent bond

Question 18

two or more atoms held together by covalent bonds

Answer 18

molecule

Question 19

a pair of shared electrons

Answer 19

single bond

Question 20

the attraction of a particular kind of atom for the electrons of a covalent bond

Answer 20

electronegativity

Question 21

a charged atom (or molecule) is called an

Answer 21

ion

Question 22

negatively charged ion

Answer 22

anion

Question 23

compounds formed by ionic bonds are called

Answer 23

ionic compounds or salts

Question 24

when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom

Answer 24

hydrogen bond

Question 25

the point at which the reactions offset one another exactly

Answer 25

chemical equilibrium

Question 26

the process that produces sugar (glucose) and oxygen from carbon dioxide and water

Answer 26

photosynthesis

Question 27

weak and occur only when atoms and molecules are very close together

Answer 27

van der Waals interactions

Question 28

because of their opposite charges, cations and anions attract each other; this attraction is called an _____

Answer 28

ionic bond

Question 29

isotopes of an element will always differ in ______

Answer 29

atomic mass

Question 30

a hydrogen bond is _____

Answer 30

a weak chemical bond

Question 31

hydrogen bonds occur when ____

Answer 31

partial opposite charges on molecules come close enough to attract eachother