Chapter 2 - Chemical Context of Life

Question 1

Essential Element

Answer 1

a chemical element required by organisms to survive, grow and reproduce
- Only 20-25% of the 92 are EE
- 96% of EE are O, C, H, N

Question 2

Trace Elements

Answer 2

an element indispensable for life but required in extremely minute amounts
- E.g. Iron(Fe)

Question 3

Atom

Answer 3

he smallest unit of matter that retains the properties of elements(something that cannot be broken down into another substance by a chemical reaction)
Composed of subatomic particles(E, N, P)

Question 4

Atom Structure

Answer 4

• Atomic Nucleus: protons and neutrons are packed tightly together
  
  • Rapid moving electrons create a cloud of negative energy around the nucleus
  • The attraction of opposite charges keep the protons within the electrons

Question 5

Dalton

Answer 5

the unit of measurement used to measure subatomic particles

- Protons and neutrons weigh approximately 1 dalton
- Electrons are too small to measure

Question 6

Atomic Number

Answer 6

the number of protons in the nucleus which is unique for each element
- To the left as a subscript
- Unless otherwise indicated atoms are neutral therefor protons and electrons are the same

Question 7

Mass Number

Answer 7

he total number of protons and neutrons in the nucleus
- Superscript to the left
- Almost all the mass is concentrated in the nucleus due to electrons weighing nothing
- if number of neutrons changes, atom becomes an isotope

Question 8

Atomic Mass

Answer 8

the total mass of an atom
- Slightly different to mass number due to small difference from electrons

Question 9

Isotope

Answer 9

an element containing several atomic forms due to different amounts of neutrons but the same amount of protons
- Can occur naturally (e.g. carbon has 3 naturally occurring isotopes)

- Because protons and electrons charges cancel each other out, when neutrons decrease in an atom, the atom doesn’t change, just the atomic mass changes
- E.g. carbon 13 has 6 protons(unchanged) and 7 neutrons(changed)

Question 10

Radioactive Isotopes

Answer 10

an isotope that is unstable resulting in the nuclei decaying spontaneously, giving off detectable particles and atoms
- Can result in a change of atoms if protons decay

- Can be used a diagnostic tools in medicine

Question 11

Radioactive Dating

Answer 11

a method for determining the absolute age of rocks and fossils based on the half life of isotopes
- Uses carbon 14 due to its radioactive nature
- By measuring the ratio of different isotopes and calculating how many half life’s have passed, they can determine how long something has been fossilized
- hey break down 50%, to 25%, to 12.5% and continually by 50%

Question 12

Atom Energy

Answer 12

the capacity to cause change especially to move matter against an opposing force

Question 13

Potential Energy

Answer 13

the energy a matter possesses as a result of its location or structure

• Matter has a tendency to move towards the lowest possible state of potential energy
• Electrons have potential energy due to their distance from the nucleus

Question 14

Electron Shell

Answer 14

an energy level of electrons at a characteristic average distance from the atom nucleus

• The further the electron is away from the nucleus, the more potential energy it carries

Question 15

What Determines how Atoms Bond

Answer 15

• The chemical behavior of an atom is determined by the distribution of electrons in the atoms valence shells

Question 16

Orbital

Answer 16

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

Question 17

Covalent Bond

Answer 17

two atoms sharing one or more pairs of valence electrons

Single bond: the sharing of 1 pair of valence electrons

Double Bond: the sharing of 2 pairs of valence electrons

Question 18

Electronegativity

Answer 18

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

- The more electronegative, the more it pulls shared electrons towards itself

- If both atoms are equally electronegative between two atoms, it’s a standoff tug of war creating a non-polar covalent bond

Question 19

Nonpolar Covalent Bond

Answer 19

a covalent bond where electrons are shared equally due to two atoms of similar electronegativity
- Strongest type

Question 20

Polar Covalent Bond

Answer 20

a covalent bond between atoms which differ in electronegativity resulting in the shared electrons being pulled towards the more electronegative atom, making it more negative and the other atom becoming more positive

Question 21

Ionic Bond

Answer 21

a bond resulting from the attraction of oppositely charged ions together due to the transfer of electrons
- The transfer of an electron is not the formation of a bond but allows the formation of a bond
Weaker bond as it is dissolved by water

Question 22

Hydrogen Bond

Answer 22

when a slightly positive hydrogen atom from a polar covalent bond is attracted to the slightly negative atom of a polar covalent bond in another molecule or region of the same molecule
- In living cells its usually between oxygen and nitrogen atoms

Question 23

Van de Waal Interactions

Answer 23

weak attractions between molecules or parts of molecules which result from local partial charges(electron distribution shifting the charges of regions)
- Can help in keeping a shape but needs another bond to change it in a shape permanently

Question 24

Isomer

Answer 24

one of two or more compounds which have the same number of atoms with the same elements but different structures and therefore different properties

Question 25

Types of Isomers: Structural

Answer 25

Structural: a compound which has the same molecular formula but differs due to the covalent arrangement of their atoms
- The bigger the carbon skeleton, the more the possible isomers
- Can also differ in the location of double bonds

Question 26

Types of Isomers: Geometric

Answer 26

Geometric Isomers: have the same molecular formular and covalent bonds between atoms but differ in the spatial arrangement of the atoms when a there are double bonds between two carbons

- Cis Isomer: when the atoms are on the same side of the double bond

- Trans Isomer: when the atoms are on opposite sides of the double bond

Question 27

Types of Isomers: Enantiomers

Answer 27

isomers which are mirror images of each other but differ in shape due to the presence of an asymmetric carbon

- Similar to hands and gloves, the 'left handed' molecule can't do the job of the 'right handed' molecule

Question 28

Chemical Reactions

Answer 28

the making and breaking of chemical bonds leading to changes in the composition of matter
- Can never destroy or create atoms, only rearrange(redistribute electrons) them

Question 29

Chemical Equilibrium

Answer 29

the state in which the rate of the forward reaction equals the rate of the reverse reaction so that the relative concentrations do not change over time