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BIOL121 > Biology Chp 2 > Flashcards

Biology Chp 2 Flashcards

The Chemical Context of Life

1
Q

Compound

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A

made of atoms joined by bonds

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2
Q

The number of protons

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A

determines an atoms identity

(Oxygen has 8 protons)

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3
Q

An atom’s electron distribution

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determines its ability to form bonds

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4
Q

A compounds properties

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depends on its atoms and how they’re bonded together

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5
Q

Matter

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anything that takes up space and has mass

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6
Q

Element

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

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7
Q

Compound

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a substance consisting of two or more different elements combined in a fixed ratio. Has characteristics different than those of its elements

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8
Q

Essential elements

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20-25% of the 92 natural elements that an organism needs to live a healthy life and reproduce

humans need 25 but plants only need 17!

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9
Q

Carbon, oxygen, hydrogen, and nitrogen

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make up about 96% of living matter

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10
Q

Calcium, phosphorous, potassium, sulfur, and a few other elements

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account for most of the remaining 4% of an organisms mass

other than carbon, oxygen, hydrogen, and nitrogen

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11
Q

Trace Elements

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A

required by an organism in only minute quantities

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12
Q

Atom

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A

the smallest unit of matter that still retains the properties of an element

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13
Q

Subatomic particles

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the smallest unit of matter that still retains the properties of an element
- neutrons (no charge), protons (positive), electrons (negative)

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14
Q

Atomic nucleus

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A

the protons and neutrons at the center of an atom

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15
Q

Dalton

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A

the unit used to measure atoms and subatomic particles

(aka atomic mass unit, amu)

Pro and Neu have masses close to 1 dalton. e- mass is negligible

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16
Q

Atomic number

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A

the number of protons an atom has

Written as a subscript to the left of the element’s symbol
The # of e- and pro generally the same

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17
Q

Mass Number

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A

the total number of protons and neutrons in the nucleus of an atom

written as a superscript to the left of an element’s symbol

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18
Q

Atomic Mass

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A

the total mass of an atom

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19
Q

Isotopes

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A

Different atomic forms of the same element

some atoms have more neutrons than others of same element

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20
Q

Radioactive isotopes

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

radioactive decay used to date fossils

21
Q

Half-life

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the time it takes for 50% of the “parent” isotope to decay

each radioactive isotope has a characteristic half-life that is not affected by temp., pressure, or any other environmental variable

22
Q

Radiometric dating

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the process used to measure the ratio of different isotopes and calculate how many half-lives(in years) have passed since an organism was fossilized or a rock was formed

23
Q

Energy

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The capacity to cause change

24
Q

Potential Energy

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the energy that matter posseses because of its location or structure

electrons have potential ebergy due to their distance from the nucleus

25
Q

Electron potential energy

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A
  • Greater distance from nucleus means greater potential energy
  • an e- potential energy is determined by its energy level
  • and e- can only exist at certain evergy levels, not between them
  • e- energy level is correlated with its average distance from the nucleus
26
Q

Electron shells

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A

Each have a characteristic ebergy level and distance from the nucleus
- 1st shell: closest to nucleus, lowest potential energy
- 2nd shell: more energy than 1st
- 3rd shell: even more energy

An e- can move from one shell to another but only 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.
As an e- absorbs energy, it moves away from the nucleus
As an e- loses energy, it moves closer to the nucleus

27
Q

Period Table layout

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A

top to bottom: increasing e- shells
left to right: addition of e- and protons

e- tend to exist in the lowest available state of potential energy
The first shell cannot hold more than 2 e-

28
Q

Valence electrons

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A

the electrons in the outermost electron shell

29
Q

Valence shell

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A

the outermost electron shell
- an atom with a complete valence shell will not interact readily with other atoms (called inert, or chemically unreactive)
- the chemical behavior of an atom depends mostly on its outermost shell

30
Q

Electron orbital

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A

the 3D space where an electron is found 90% of the time

  • 1st shell has one orbital (s)
  • 2nd shell has four orbitals; one spherical(2s) and three dumbell-shaped orbitals (2p)
  • no more than 2 e- can inhabit a single orbital
  • reactivity of an atom arises from presence of unpaired e- in one or more orbitals
31
Q

Chemical bonds

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A

Attractions that hold atoms close together after the transferring and/or sharing of e-

covalent bonds in molecules and ionic bonds in dry ionic compounds are the strongest

32
Q

Covalent Bonds

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the sharing of a pair of valence electrons by two atoms

33
Q

Molecule

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A

two or more atoms held together by covalent bonds

34
Q

Valence

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A

the bonding capacity of an atom

usually equals the number of e- required to complete valence shell

35
Q

Compound

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A

Combination of two or more different elements

36
Q

Electronegativity

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A

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

37
Q

Non-polar covalent bond

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A

when 2 atoms have the same electronegativity

38
Q

Polar covalent bond

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A

when the electrons of the bond are not shared equally

39
Q

Ionic Bonds

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opposite charges of ions attract one another

40
Q

Ions

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when an atom strips another of its electron, resulting in 2 oppositely charged atoms/molecules

41
Q

Anion

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a negatively charged ion

42
Q

Cation

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A

a positively charged ion

43
Q

Ionic Compounds

Salts

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A

Compounds formed by ionic bonds
- 3D lattice structure
- Does not consist of molecules, the formula indicates ratios

44
Q

Hydrogen Bonds

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A

the noncovalent attraction between a hydrogen (already covalently bonded) and an electronegtive atom. Weak bonds

Ex.) h-bonds in water between electroneg. oxygen and hydrogen

45
Q

Van der Waals Interactions

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the ever changing regions of positive amd negative charge that enable all atoms and molecules to stick to one another. Weak bonds

46
Q

Biological molecules bind together temporarily only if their

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shapes are complementary

47
Q

Molecular shape is determined by

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A

the position of orbitals

in a covalent bond, s and p orbitals may hybridize, creating specific molecular shapes

48
Q

Reactants

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A

the starting molecules of a chemical reaction

49
Q

Products

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the final molecules of chemical reactions

BIOL121 (5 decks)

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