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Flashcards in Chapter 2 Deck (93):
1

wood ants

shoot formic acid to defend against invaders

2

Matter consists of ___ in pure form and in combinations called ___.

chemical elements, compounds.

3

element

substance that can't be broken down to other substances by chemical reactions

4

How many naturally occurring elements are there?

92 elements

5

compound

substance consisting of 2+ different elements combined in a fixed ratio. (eg. NaCl)
has different characteristics from that of its elements

6

essential elements

20-25% of the natural elements
needed by an organism to live a healthy life and reproduce

7

What elements make up 96% of living matter?

carbon, oxygen, hydrogen, nitrogen

8

trace elements

required by an organism only in minute quantities

9

What elements are trace elements?

boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, zinc

10

goiter

when the thyroid gland swells to abnormal size due to lack of iodine

11

arsenic

poisonous to humans

12

serpentine

jade-like material with elevated concentrations of chromium, nickel, cobalt

13

evolution of tolerance to serpentine

some plants evolved over time (natural selection) to survive in serpentine soils

14

An element's properties depend on the ____.

structure of its atoms.

15

atom

smallest unit of matter that still retains properties of an element

16

subatomic particles

make up atoms
neutron, proton (+), electron (-)

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atomic nucleus

dense core made of protons and neutrons, surrounded by cloud of electrons (attracted by charge)

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mass of proton/neutron

1.7 x 10^-24 g/1 Dalton

19

dalton

unit of measurement same as 1 amu

20

atomic number

number of protons of a certain element
written in subscript on the left of the symbol
usually indicates number of electrons as well, IF atom isn't an ion

21

mass number

sum of protons + neutrons
superscript to the left of the symbol

22

atomic mass

total mass of an atom

23

isotopes

different atomic forms of the same element, with different neutron number
have greater masses

24

radioactive isotope

unstable, nucleus decays spontaneously, gives off particles and energy

25

radioactive tracers

radioactive atoms put into bloodstream to diagnose certain disorders (eg. kidney disease)

26

PET scanners

monitor growth and metabolism of cancers in the body

27

dangers of decaying isotopes

radioactive fallout
severity depends on amount/type of radiation

28

radiometric dating

used to date fossils
measure ratio of different isotopes and calculate how many half-lives have passed since an organism was fossilized

29

half-life

parent isotope decays into daughter isotope
amount of time for 50% of parent to decay

30

Which subatomic particles are responsible for chem reactions?

electrons

31

energy

capacity to cause change (eg. by doing work)

32

potential energy (PE)

energy matter possesses b/c of its location/structure

33

What is matter's natural tendency?

to move towards the lowest possible state of potential energy

34

Skills Exercise: Neanderthal Extinction

-used carbon-14 dating to determine age of Neanderthal fossil from most recent layer
-half-life of carbon-14 is 5,730 years
-fossil had ~ 0.0078 as much carbon-14 as the atmosphere

35

potential energy of an electron is from:

-their distance from the nucleus; the more distant an electron is from the nucleus, the greater the potential energy
-energy level; can't exist between energy levels, only at certain ones

36

electron shells

have characteristic average distance and energy level
where electors are found
represented by concentric circles
first shell = closest to nucleus (lowest PE)
contain electrons at a particular energy level

37

Can electrons move between shells? How?

Yes, but only by absorbing/losing amount of energy equal to the difference in PE between its position in the old and new shell

38

When an electron absorbs energy:

it moves to a shell further from the nucleus

39

When an electron "falls back" to a shell:

the lost energy is released into the enviro as heat

40

Chemical behavior of an atom is determined by the:

distribution of electrons in the electron shells

41

How many electrons can the first shell hold?

2 electrons

42

How many electrons can the second, third, etc shells hold?

8 electrons

43

The outermost shell determines:

the chemical behavior of an atom, based on the NUMBER of electrons in it

44

valence shell/valence electrons

the outermost shell and outermost electrons
unpaired electrons react

45

Atoms with full valence shells will:

not react w/ other atoms; inert

46

Each concentric circle in a 2D drawing:

represents only the average distance between an electron in that shell and then nucleus

47

orbital

3D space where an electron is found 90% of the time
component of an electron shell
no more than 2 electrons can occupy a single orbital
4 orbitals of the second electron shell = up to 8 electrons

48

types of orbitals

1st electron shell: only one spherical s orbital (1s)
2nd electron shell: 4 orbitals, 1 large spherical s orbital (2s), 3 dumbbell-shapped p-orbital (2p orbitals)

49

Formation and function of molecules depend on ____ between ___

chemical bonding, atoms.

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chemical bonds

attractions between atoms that interact

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covalent bonds

sharing of a pair of valence electrons by 2 atoms

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molecule

2+ atoms held togeterh by covalent bonds

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molecular formula

indicates how many atoms in the molecule (eg. H2)

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Lewis Dot structure

element symbols are surrounded by dots that represent the valence electrons (eg. H:H)

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structural formula

line represents single bond; double bond is two lines (eg. H-H, or O=O)

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valence

bonding capacity of an atom corresponding to # of covalent bonds they can form; equals # of unpaired electrons required to complete the atom's outermost shell

57

electronegativity

attraction of a particular atom for the electrons of a covalent bond; more electronegative = more strongly it pulls shared electrons toward itself

58

nonpolar covalent bond

electron is shared equally between 2 atoms; same electronegativity

59

polar covalent bond

electron not shared equally b/c differing electronegativities (eg. water = very polar b/c oxygen is very electronegative)

60

partial negative

caused by polar covalent bonds
indicated w/ delta signs

61

ions

two oppositely charged atoms (b/c electron stripped away from another)
applies to molecules that are electrically charged

62

cation

positively charged ion

63

anion

negatively charged ion

64

ionic bond

bond between any two oppositely charged ions (eg. sodium and chlorine)

65

ionic compounds/salts

compounds formed by ionic bonds
often found as crystals in nature
made of vast #s of cation ions and anions bound by electrical attraction and arranged in 3D lattice
*IS NOT a molecule

66

importance of weaker bonds

-two molecules can come together, respond, then separate
(eg. water and ionic bond, hydrogen bonds and van der Waals)

67

hydrogen bond

attraction between a hydrogen and an electronegative atom (when covalently bonded w/ electroneg atom, has slight pos charge that allows it to be attracted to diff electroneg atom nearby)

68

van der Waals interactions

individually very weak; occur only when atoms and molecules are very close together
constantly changing regions of pos/neg charge in molecules

69

linear shape

molecule consisting of two atoms

70

Molecule shape is determined by:

position of atoms' orbitals
(eg. atoms w/ valence electrons in both s and p orbitals form 4 new hybrid orbitals shaped like teardrops from region of atomic nucleus; if connect larger ends w/ lines, have a tetrahedron)

71

importance of molecular shape

determines how biological molecules recognize and respond to one another / specificity (only bind temporarily if their shapes are complementary)
(eg. opiates, which relieve pain and alter mood by weakly binding to specific receptor mollies on brain cell surfaces; have shapes similar to endorphins)

72

Chemical reactions ___ and ____ chemical bonds.

make, break

73

chemical reactions

making/breaking of chemical bonds, leading to changes in composition of matter (eg. hydrogen and oxygen reaction forms water by breaking covalent bonds of H2 and O2 and forming new bonds for H2O)

74

reactants

starting materials, on L of equations

75

products

ending materials, on R of equations

76

In chemical reactions, matter is:

conserved. Reactions can only rearrange electrons

77

All chemical reactions are:

reversible

78

factor that affects rate of reaction

concentration of reactants; greater concentration = more collisions = more opportunities to react and form products

79

chemical equilibrium

point at which the reactions offset one another exactly
is a dynamic equilibrium (reactions still going on) w/ no net effect on reactant/product concentrations
*equilibrium does NOT mean reactants and products are equal in concentration, but that their concentrations have stabilized at a particular ratio (eg. ammonia)

80

strongest chemical bonds

ionic and covalent

81

glucose

C6H12O6
alpha glucose vs beta glucose = reversal of H and OH on first carbon

82

fructose

C6H12O6, placement of C atoms = diff

83

glycosidic linkage

connects 2 sugar molecules, disaccharide, loses water molecule as does so --> condensation reaction, dehydration reaction

84

starch

polymer of alpha glucose molecules; energy storage in plant cells

85

glucogen

polymer of alpha molecules; differs in pattern of polymer branching; energy storage in animal cells

86

cellulose

[polymer of beta glucose; structural molecule in walls of plants, major componenet of wood

87

chitin

beta glucose molec w/ N containing group attached to ring; structural molecule in walls of fungus cells; exoskeletons

88

tryglycerides

fats and oils, 3 fatty acids attached to glycerol molecule
-fatty acids = hydrocarbons (covalently bonded C and H w/ carboxyl group (COOH) at end)
-double bond in fatty acid creates bend --> saturated fats

89

saturated fats

packed tightly, higher melting point
-single covalent bond btwn each pair of C, each C has 2 H bonded to it (saturated w/ H)

90

unsaturated fats

-liquid at room temp
-lower melt temp

91

monounsaturated fatty acid

1 double covalent bond, each of 2 C in bond has only 1 H bonded to it

92

polyunsaturated fatty acid

2+ double covalent bonds

93

phospholipid

looks like triglyceride
-one of fatty acid chains replaced by phosphate group