chem midterm Flashcards
Different substances evenly mixed ex: sugar water, salt water
Homogenous mixture
Different substances not evenly mixed ex: trail mix, cereal
heterogeneous mixture
The digits that carry meaning and contribute to its precision
Significant figures.
The measure of how much mass is in a given volume
density
Amount of matter an object contains
mass
spaced occupied by a 3 dimensional shape
volume
the average mass of an atom of an element (measured in AMU)
Atomic mass
The # of protons in the nucleus of an atom of that element
Atomic number
Different forms of an element might have the same number of protons but a different number of neutrons (These variations result in a different atomic mass)
Isotope
An atom or group of bonded atoms that has a positive charge (cation) or negative charge (anion)
Ion
of protons and neutrons in the nucleus
Mass number
The spontaneous emission of radiation from the nucleus of an unstable atom
Radioactivity
The time it takes for half of the atoms in a sample to undergo radioactivity decay
half-life
The amount of a substance that contains as many particles as there are atoms in exactly 12 g or carbon 12
Mole
A form of energy that exhibits wave-like behaviors as it travels through space
electromagnetic radiation
The lowest state of an atom
ground state
A state in which an atom has a higher potential energy than its ground state
Excited state
(lambda) the distance from crest to crest
wavelength
(Nu) the number of waves that pass a given point on a specific time– usually one second (waves per second)
frequency
A particle of electromagnetic radiation (ER) having no mass and carrying a quantum (fixed amount) of energy
Photon
a single packet of matter or energy
quantum
a three-dimensional region around the nucelus that indicates the probable location of an electron.
orbital
arrangement of electrons in an atom or ion. Describes how electrons ocupy different sublevels or orbitals.
electron configuration
Electrons are arranged in an atom such that each electron occupies the lowest energy orbital available
Aufbau principle
Electrons should be placed into separate orbitals before going to the same orbitals
Hund’s rule
Two arrows cant go on the same orbital
Pauli exclusion
Electronegativity increases across a….
period
Energy decreases down a…
group
negatively charged ion
anion
postively charged ion
cation
metal
good conductors of heat and electricity
the chemical bonding that results from the electrical attraction between laerge number of cations and anions that have been created by the transfer of electrons.
ionic bond
properties opposite to metals, made from ions
non-metal
substances that conduct electricity when dissolved in water or melted
electrolytes
elements that have properties intermediate between metals and non-metals
metalloid (semi-metal)
highly reactive, first row of periodic table
alkali metals
Alkaline earth metals
second row of the periodic table
group 17 of the periodic table, highly reactive and tend to form compouds by gaining electrons from other elements
halogen
group 18, low reactivity, full outer electron shell, stable
noble gases
one half the distance between the nuclei of identical atoms that are bound together
atomic radius
a measure of the ability of an atom in a compound to atraxct the valence elections of another atom in that compound on isolated atoms
electronegativity
the energy required to remove one electron from a neutral atom of an element (measured in the gas phase)
ionization energy
the electrons occupying the atoms highest energy level (they are always in the S and P orbitals)
Valence electrons
Why do certain elements emit radioactivity?
An unfavorable ratio of neutrons to protons can yeild an unstable atom emitting radioactivity (particles/energy) make the atom more stable.
What are the forms of radioactive decay?
Alpha, Beta, Gamma
what happens when an element emits alpha radiation?
4/2He: subtract 4 from the top number and 2 from the bottom number
what happens when an element emits beta radiation?
0/-1e: add 1 to the bottom number
Kilo- (King)
1,000
Hecto-(henry)
100
Deka-(died)
10
Deci-(drinking)
1/10
centi-(chocolate)
1/100
milli-(milk)
1/1000
Micro-
1/1000000
What happens to an electron in an atom if it aborbs a quantym of energy? What happens when it loses energy?
An electron that abosrbs a quantum of energy will jump to an excited state and when it loses energy it decays and drops down to a ground state.
What is a valence electron? How can you determine the # of valence electrons for any given element?
valence electrons are the electrons with the most energy. They are the furthest electrons from the nucelus and are responsible fo rthe characterisitifcs of that element. The number of valence elections for the main block elemernts (those elements in the s + p blocks) is found from the group number: group 1=1, group 2=2, group 13=3, group 14=4, group 15=5, group 16=6, group 17=7 ground 18=8.
Which groups of elements are the most reactive?
group 1, the alkali metals and group 17, the halogens
