Chapter 2 - Chemical Context of Life Flashcards
Essential Element
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
Trace Elements
an element indispensable for life but required in extremely minute amounts
- E.g. Iron(Fe)
Atom
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)
Atom Structure
- 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
Dalton
the unit of measurement used to measure subatomic particles
- Protons and neutrons weigh approximately 1 dalton - Electrons are too small to measure
Atomic Number
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
Mass Number
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
Atomic Mass
the total mass of an atom
- Slightly different to mass number due to small difference from electrons
Isotope
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)
Radioactive Isotopes
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
Radioactive Dating
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%
Atom Energy
the capacity to cause change especially to move matter against an opposing force
Potential Energy
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
Electron Shell
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
What Determines how Atoms Bond
- The chemical behavior of an atom is determined by the distribution of electrons in the atoms valence shells
Orbital
the 3d space where an electron is found 90% of the time
Covalent Bond
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
Electronegativity
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
Nonpolar Covalent Bond
a covalent bond where electrons are shared equally due to two atoms of similar electronegativity
- Strongest type
Polar Covalent Bond
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
Ionic Bond
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
Hydrogen Bond
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
Van de Waal Interactions
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
Isomer
one of two or more compounds which have the same number of atoms with the same elements but different structures and therefore different properties
Types of Isomers: Structural
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
Types of Isomers: Geometric
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
Types of Isomers: Enantiomers
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
Chemical Reactions
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
Chemical Equilibrium
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
