Chapter 2

Question 1

Matter

Answer 1

Anything that has mass and takes up space

Question 2

Element (92 naturally occurring elements)

Answer 2

A substance that cannot be broken down to other substances by chemical reactions. (92 naturally occurring elements)

Question 3

Compound

Answer 3

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

Question 4

Essential elements (20 - 25% of elements)

Answer 4

Elements that an organism needs to live a healthy life and reproduce. Humans require 25 elements

Question 5

Trace elements

Answer 5

Elements required by an organism in only minute quantities. Iron (all forms of life) Iodine (thyroid gland)

Question 6

96% of living matter

Answer 6

Just four elements—oxygen (O), carbon (C), hydrogen

(H), and nitrogen (N). COHN

Question 7

Subatomic particles

Answer 7

Neutrons (neutral), protons (positive) and electrons (negative)

Question 8

Atomic nucleus

Answer 8

The dense (positively charged) core at the center of an atom that contains neutrons and protons.

Question 9

Dalton

Answer 9

A unit of mass a.k.a as amu (atomic mass unit). Protons and neutrons have masses close to 1 dalton. The mass of an electron is 1/2000 of a dalton.

Question 10

Atomic number

Answer 10

The number of protons in an atom of a specific element. All atoms of a particular element have the same number of protons in their nuclei. Subscript to the left

Question 11

Mass number

Answer 11

The sum of protons plus neutrons in the nucleus of an atom. Superscript to the left

Question 12

Atomic mass

Answer 12

The total mass of an atom, close to its mass number (weighted average)

Question 13

Isotopes

Answer 13

Different atoms of the same element that have different number of neutrons

Question 14

Radioactive isotope

Answer 14

An isotope in which the nucleus decays spontaneously, giving off particles and energy which can transform the atom to an atom of a different element

Question 15

Radioactive tracer

Answer 15

Radioactive isotopes that are incorporated into biologically active molecules, which are then used as tracers to track atoms during metabolism, the chemical processes of an organism

Question 16

Half-life

Answer 16

The time it takes for 50% of the parent isotope to decay into its daughter isotope

Question 17

Radiometric dating

Answer 17

Technique used to date materials by measuring the ratio of different isotopes present in the sample

Question 18

Energy

Answer 18

The capacity to do work

Question 19

Potential energy

Answer 19

The energy that matter possesses because of its location or structure

Question 20

Valence electrons

Answer 20

The electrons in the outermost electron shell

Question 21

Valence shell

Answer 21

The outermost electron shell

Question 22

Noble gases

Answer 22

Gases that have completed valence shells. They are chemically inert

Question 23

Electron shell

Answer 23

An orbit of electrons with a particular energy level and average distance from the nucleus

Question 24

Chemical bond

Answer 24

An attraction between atoms that binds them together

Question 25

Covalent bond

Answer 25

The sharing of a pair of valence electrons by two atoms

Question 26

Molecule

Answer 26

Two or more atoms held together by covalent bonds

Question 27

Single bond

Answer 27

One pair of shared electrons

Question 28

Double bond

Answer 28

Two pairs of shared electrons

Question 29

Valence

Answer 29

The bonding capacity of an atom which usually equals the number of unpaired electrons required to complete the valence shell

Question 30

Electronegativity

Answer 30

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

Question 31

Polar covalent bond

Answer 31

A covalent bond whose electrons are not shared equally between the atoms giving each atom a partial charge

Question 32

Ion

Answer 32

A charged atom or molecule that has gained or lost an electron

Question 33

Cation

Answer 33

A positively charged atom or molecule

Question 34

Anion

Answer 34

A negatively charged atom or molecule

Question 35

Salt

Answer 35

Ionic compound. Compound formed by ionic bonds

Question 36

Ionic bond

Answer 36

The attraction between two oppositely charged ions. An ionic bond can form when one atom transfers an electron to another atom

Question 37

Weak bonds

Answer 37

Ionic bonds between ions dissociated in water, hydrogen bonds and van der Waals bonds. Weak bonds reinforce the three dimensional shape of large molecules (proteins)

Question 38

Hydrogen bond

Answer 38

The attraction between an hydrogen atom and an electronegative atom

Question 39

Van der Waals interactions

Answer 39

The charges that result in an atom by the random accumulation of electrons in one region

Question 40

Chemical reaction

Answer 40

Involves the forming or breaking of a chemical bond

Question 41

Reactant

Answer 41

A starting material in a chemical reaction

Question 42

Product

Answer 42

The product of a chemical reaction

Question 43

Chemical equilibrium

Answer 43

The forward and reverse reactions occur at the same rate. It is a dynamic equilibrium