Ap Bio Chapter 2

Front 1

mass

Back 1

amount of matter in an object

Front 2

weight

Back 2

how strongly that mass is pulled by gravity

Front 3

element

Back 3

a substance that canot be broken down to other substances by chemical reactions

Front 4

compound

Back 4

A substance consisting of 2 or more different elements combined in a fix ratio. Ex: Table salt (NAcL

Front 5

most abundunt chemical elements

Back 5

Carbon, Nitrogen, Oxygen, Hydrogen

Front 6

atomic #

Back 6

# of protons

Front 7

mass number

Back 7

protons+neutrons

Front 8

atomic mass

Back 8

approx of total mass

Front 9

isotopes

Back 9

Some atoms have more neutrons than other atoms of the same element and thus have greater masses

Front 10

radioactive isotope

Back 10

one in which the nucleus decays spontaneously, giving off particles and energy

Front 11

potential energy

Back 11

the energy that matter possesses because of its location or structure. For example, because of its altitude, water in a reservoir on a hill has potential energy.

Front 12

definition of energy

Back 12

capacity to cause change

Front 13

how does an atom get greater potential energy

Back 13

It takes work to move an electron farther away from the nucleus, so the more distant the electrons are from the nucleus, the greater their potential energy

Front 14

how can changes in potential energy occur?

Back 14

only in fixed amounts
an electron cannot exist in between fixed states of potential energy

Front 15

how can electron change the energy shell it occupies?

Back 15

by absorbing or losing an amount of energy equal to the difference in potential energy between its position in the old shell and that in the new shell. When an electron absorbs energy, it moves to a shell farther out from the nucleus. For example, light energy can excite an electron to a higher energy level

Front 16

how does an electron "lose" energy

Back 16

When an electron loses energy, it “falls back” to a shell closer to the nucleus, and the lost energy is usually released to the environment in the form of heat

Front 17

first shell / second shell

Back 17

2 electrons
second shell:

Front 18

what does the chemical behavior of an atom depend mostly on

Back 18

number of electrons in its outermost shell. We call those outer electrons valence electrons and the outermost electron shell the valence shell.

Front 19

what kind of atoms exhibit similar chemical behavior?

Back 19

atoms with the same # of electrons in their valence shells

Front 20

why do we describe the orbitals and not the exact path

Back 20

In reality, we can never know the exact path of an electron. What we can do instead is describe the space in which an electron spends most of its time. The three–dimensional space where an electron is found 90% of the time is called an orbital.

Front 21

define a molecule

Back 21

2 or more atoms held together by a covalent bond

Front 22

atom's valence

Back 22

the bonding capacity of an atom and usually equals the # of unpaired electron in the valence shell

Front 23

pure elements

Back 23

h2 AND 02 (NOT COMPOUND)

Front 24

natural gas

Back 24

CH methane

Front 25

electronegativity and what if something is more electronegative

Back 25

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

more electronegative an atom, the more strongly it pulls shared electrons toward itself. In a covalent bond between two atoms of the same element, the outcome for the common electrons is a standoff beucas ethey are equally electronegative.

Front 26

electrons shared equally

Back 26

nonpolar covalent bond H2

Front 27

polar covalent bond

Back 27

where one atom is bonded to a more electronegative atom, the electrons of the bond are not shared equally.

Front 28

charged positive ion

Back 28

cation

Front 29

negative charged ion

Back 29

anion

Front 30

salts

Back 30

compounds formed by ionic bonds

Front 31

what has a big effect on the strength of ionic bonds?

Back 31

envrionment

Front 32

how do hydrogen bonds form?

Back 32

when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. In living cells, the electronegative partners involved are usually oxygen or nitrogen atoms.

Front 33

van der waals

Back 33

ever–changing “hot spots” of positive and negative charge that enable all atoms and molecules to stick to one another. These van der Waals interactions are weak and occur only when atoms and molecules are very close together

Front 34

starting materials

Back 34

reactants

Front 35

what do the coefficients signify

Back 35

the # of molecules involved

Front 36

what is an important factor that affects the rate of reactions?

Back 36

the concentration of reactants. The greater the concentration of reactant molecules, the more frequently they collide with one another and have an opportunity to react to form products. The same holds true for the products. As products accumulate, collisions resulting in the reverse reaction become increasingly frequent. Eventually, the forward and reverse reactions occur at the same rate, and the relative concentrations of products and reactants stop changing

Front 37

chemical equilibirum

Back 37

The point at which the reactions offset one another exactly is called chemical equilibrium. This is a dynamic equilibrium; reactions are still going on, but with no net effect on the concentrations of reactants and products. Equilibrium does not mean that the reactants and products are equal in concentration, but only that their concentrations have stabilized at a particular ratio