Chapter 2: chemistry

Question 1

An element is a substance that

Answer 1

cannot be broken down to other substances by chemical reactions

Question 2

A compound is a substance

Answer 2

consisting of two or more elements in a fixed ratio

Question 3

what elements make up 96% of living matter?

Answer 3

Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter

Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur

Question 4

Atoms are composed of subatomic particles​

Answer 4

Relevant subatomic particles include:​

Protons (positive charge)​

Neutrons (no electrical charge)​

Electrons (negative charge)​

Question 5

Neutrons and protons form the

Answer 5

atomic nucleus​

Question 6

____ form a cloud around the nucleus

Answer 6

Electrons form a cloud around the nucleus

Question 7

An element’s atomic number is

Answer 7

the number of protons in its nucleus

Question 8

An element’s atomic mass number is

Answer 8

the sum of protons plus neutrons in the nucleus

Question 9

___ are atoms of an element that differ in number of neutrons

Answer 9

Isotopes

Question 10

____ decay spontaneously, giving off particles and energy

Answer 10

Radioactive Isotopes

Question 11

Some applications of radioactive isotopes in biological research are:​

Answer 11

Dating fossils​

Tracing atoms through metabolic processes​

Diagnosing medical disorders

Question 12

___ is the capacity to cause change

Answer 12

Energy

Question 13

___ is the energy that matter has because of its location or structure

Answer 13

Potential energy

Question 14

An electron’s state of potential energy is called its energy level, or ___

Answer 14

electron shell

Question 15

___ are those in the outermost shell, or ___

Answer 15

Valence electrons, valence shell

Question 16

The chemical behavior of an atom is mostly determined by the ___

Answer 16

valence electrons

Question 17

Elements with a full valence shell are ___

Answer 17

chemically inert

Question 18

Atoms with incomplete valence shells can…

Answer 18

share or transfer valence electrons with certain other atoms

Question 19

atoms staying close together, held by attractions called ___

Answer 19

chemical bonds

Question 20

A ___ is the sharing of a pair of valence electrons by two atoms

Answer 20

covalent bond

In a covalent bond, the shared electrons count as part of each atom’s valence shell

(example 2 Hydrogen atoms. both have 1 electron in the first shell. H2 would let them share their electrons completing their first shell with now 2 electrons)

Question 21

A ___ consists of two or more atoms held together by covalent bonds

Answer 21

molecule

Question 22

A single covalent bond, or ___, is the sharing of one pair of valence electrons

Answer 22

single bond

Question 23

A double covalent bond, or ___, is the sharing of two pairs of valence electrons

Answer 23

double bond

Question 24

The notation used to represent atoms and bonding is called a ___

For example, H–H

Answer 24

structural formula​

Question 25

a ___ ​

For example, H2

Answer 25

molecular formula

Question 26

A compound is a combination of two or more ___ elements

Answer 26

different

Question 27

In a ___ covalent bond, the atoms share the electron equally

Answer 27

nonpolar

Question 28

In a ___ covalent bond, the atoms do not share the electron equally

Answer 28

polar

Question 29

Atoms sometimes strip electrons from their bonding partners​

An example is the transfer of an electron from sodium to chlorine​

Answer 29

ion

Question 30

A ___ is a positively charged ion

Answer 30

cation

Question 31

An ___ is a negatively charged ion

Answer 31

anion

Question 32

An ___ is an attraction between an anion and a cation

Answer 32

ionic bond

Question 33

Compounds formed by ionic bonds are called

___, or salts

Answer 33

ionic compounds

Question 34

A __ forms when a hydrogen atom covalently bonds to one electronegative atom and is also attracted to another electronegative atom

Answer 34

hydrogen bond

(for instance a single hydrogen atom that’s bonded with an oxygen atom (let’s say H20) attracts a negatively charged oxygen atom from another H20 molecule)

Question 35

___ interactions are weak attractions between molecules that are close together.

Answer 35

Van der Waals

Question 36

A ___ is usually very important to its function

Answer 36

molecule’s shape

Biological molecules recognize and interact with each other with a specificity based on molecular shape​

Molecules with similar shapes can have similar biological effects

Question 37

___ are the making and breaking of chemical bonds

Answer 37

Chemical reactions

Question 38

The starting molecules of a chemical reaction are called ___

Answer 38

reactants

Question 39

The final molecules of a chemical reaction are called ___

Answer 39

products

Question 40

The number of atoms on the reactant side MUST BE ___ to the number of atoms on the product side.

Answer 40

EQUAL

Question 41

The tendency of an atom to pull electrons toward itself is referred to as its

Answer 41

electronegativity