Chemical Context of Life (Unit 1)

Question 1

Organisms are composed of —–

Answer 1

Matter

Question 2

Matter is

Answer 2

anything that takes up space and has mass

Question 3

Element

Answer 3

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

Question 4

Compound

Answer 4

a substance consisting of two or more elements in a fixed ratio
- characteristics different from those of its elements

Question 5

4 elements that make up 96% of life

Answer 5

Carbon, hydrogen, oxygen, and nitrogen

Question 6

Trace elements

Answer 6

required by an organism in only minute quantities

Question 7

Examples of trace elements

Answer 7

4% consists of calcium, phosphorus, potassium, and sulfur

Question 8

3 subatomic particles

Answer 8

Neutrons (no electrical charge)
Protons (positive charge)
Electrons (negative charge)

Question 9

What particles form the atomic nucleus?

Answer 9

Neutrons and protons

Question 10

Relation of neutron mass and proton mass

Answer 10

measured in daltons and equal to each other

Question 11

Atomic number

Answer 11

number of protons in its nucleus

Question 12

Elemental Mass Number

Answer 12

sum of protons plus neutrons in the nucleus

Question 13

Atomic Mass

Answer 13

the atom’s total mass, can be approximated by the mass number

Question 14

Atoms in Element *Number of Protons and Neutrons

Answer 14

Proton- Same in all atoms of element
Neutron- can be different

Question 15

Isotopes

Answer 15

two atoms of an element that differ in number of neutrons

Question 16

Radioactive isotopes

Answer 16

decay spontaneously, giving off particles and energy

Question 17

What gives elements their property?

Answer 17

Protons

Question 18

Radioactive isotopes are often used for?

Answer 18

diagnostic tools in medicine

Question 19

Radioactive tracers

Answer 19

can be used to track atoms through metabolism

Question 20

Radiometric Dating

Answer 20

scientists measure the ratio of different isotopes and calculate how many half-lives have passed since the fossil or rock was formed

Question 21

Half-Life

Answer 21

A “parent” isotope decays into its “daughter” isotope at a fixed rate, expressed as the half-life
They can vary from seconds o days.

Other Definition: The half-life of a reaction is the time required for the reactant concentration to decrease to one-half its initial value.

Question 22

Valence electrons

Answer 22

are those in the outermost shell, or valence shell

Question 23

Valence Electrons determine

Answer 23

chemical behavior of an atom

Question 24

What does having a full valence shell mean?

Answer 24

The atom is chemically inert

Question 25

Orbital

Answer 25

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

Question 26

Chemical Bonds

Answer 26

Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms

These interactions usually result in atoms staying close together, held by attractions called
chemical bonds

Question 27

Covalent Bond

Answer 27

• The sharing of a pair of valence electrons by two atoms

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

Question 28

Molecule

Answer 28

consists of two or more atoms held together by covalent bonds

Question 29

Double Bond vs Single Bond

Answer 29

• A single covalent bond, or single bond, is the sharing of one pair of valence electrons
• A double covalent bond, or double bond, is the sharing of two pairs of valence electrons

Question 30

Electronegativity

Answer 30

an atom’s attraction for the electrons in a covalent bond

Question 31

The more electronegative an atom is, the …….

Answer 31

The more electronegative an atom is, the more strongly it pulls shared electrons toward itself

Question 32

nonpolar covalent bond

Answer 32

the atoms share the electron equally

Question 33

polar covalent bond

Answer 33

one atom is more electronegative

the atoms do not share
the electron equally

Question 34

ION

Answer 34

A charged atom (or molecule) is called an ion

Question 35

Disassociate

Answer 35

when ion is placed in water

Question 36

Cation

Answer 36

A cation is a positively charged ion

Question 37

Anion

Answer 37

An anion is a negatively charged ion

Question 38

ionic bond

Answer 38

An ionic bond is an attraction between an anion and a cation

Question 39

ionic compounds/ salts

Answer 39

Compounds formed by ionic bonds are called ionic compounds, or salts

Question 40

Strongest bonds

Answer 40

Covalent Bonds

Question 41

Hydrogen Bond

Answer 41

bond forms when a hydrogen atom covalently bonded to one electronegative atom

Question 42

Van der Waals interactions

Answer 42

are attractions between molecules that are close together as a result of electrons that are not evenly distributed, they may accumulate by chance in one part of a molecule

Question 43

A molecule’s — and —– are key to its function

Answer 43

A molecule’s size and shape are key to its function

Question 44

A molecule’s shape is determined by the

Answer 44

A molecule’s shape is determined by the positions of its atoms’ orbitals