Chapter 2 Flashcards
matter
anything that takes up space and has mass
Ex: rocks, oils, gases
element
substance that cannot be broken down into other substances by chemical reaction
o 92 elements
compound
substance consisting of two or more elements combined in a fixed ratio
Ex: Emergent properties: Compound has different properties than element.
Essential elements
20-25% of the natural elements an organism needs to live a healthy life and reproduce (~25 elements)
o O, C, H, N (make 96% living matter) Ca, P, K, S
Trace elements
required by organism in small quantities only
o Ex: Fe, I (vertebrates)
Atom
the smallest unit of matter that still retains the properties of an element o Subatomic particles • Neutrons • Protons: no of protons identifies atom • Electrons
mass number
sum of p+n
atomic number
number of protons
Isotopes
different atomic forms of the same element
o Same amount of protons, different amount of NEUTRONS
Radioactive isotope
nucleus decays spontaneously, giving off particles and energy
half life
amount it takes for ½ of parent isotope to decay into daughter isotope
radiometric dating
process through which scientists measure the ratio of different isotopes to calculate how many half lives (in years) have passed since organism has fossilized
energy
the capacity to cause change, for instance, by doing work
electron shells
have characteristic distance and energy level
o Represents average distance between electron and the nucleus
valence shell
outermost shell of electrons
orbital
the 3D space where an electron is found 90% of the time
electronegativity
the attraction of a particular atom for the electrons of a covalent bond
ions
two oppositely charged atoms
ionic bond
transfer of electrons, significant electronegativity difference
ionic compounds/salts
compounds formed by ionic bonds
o Consist of lattice anions and cations
Hydrogen bond
attraction between H and electronegative atom (usually O or N)
Van der Waals forces
charge is not always evenly distributed. Positive and negative regions change.
Ex: these allow a gecko to walk up a wall
Law of Conservation of Atoms
Atoms are neither created or destroyed, but rearranged.
chemical equilibrium
forward and reverse reactions occur at same rate and offset each other.
o Dynamic
o There is not net effect on concentrations of reactants or products.
o Reacts & products are NOT at equal concentrations but have stabilized at a particular ratio.
