a unit or quantum of light; a particle of electromagnetic radiation that has zero rest mass and carries a quantum of energy
law of definite proportions
the law that states that a chemical compound always contains the same elements in exactly the same proportions by weight or mass
an atom that has the same number of protons as other atoms of the same element but do that has a different number of neutrons
the study of the structure and behavior of the atom and of subatomic particles from the view that all energy comes in tiny, indivisible bundles.
the radiation associated with an electric and magnetic field; it varies periodically and travels at the speed of light
average atomic mass
the weighted average of the masses of all naturally occurring isotopes of an element
line emission spectrum
a diagram or graph that indicates the degree to which a substance emits radiant energy with respect to wavelength
the uninterrupted broad band of all colors (wavelengths) emitted by incandescent solids
photo electric affect
the emission of electrons from a material when light of certain frequencies shines on the surface of the material
the number of cycles or vibrations per unit of time; also the number of waves produced in a given amount of time
the Sl base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly 12 g of carbon 12
adding or subtracting decimals (sig figs)
the answer must have the same number of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point.
multiplication/division w/ sig figs
the answer can have no more sig figs than are in the measurement with the fewest number of sig figs
law of conservation of mass
mass is neither created nor destroyed during ordinary chemical reactions or physical changes.
law of multiple proportions
if two or more compounds are composed of the same two elements, then the ratio of the masses of the second element combined with certain mass of the first element it always a ration of small whole numbers
Dalton's atomic theory
1. all matter is composed of extremely small particles called atoms
2. atoms of an element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties
3. atoms cannot be subdivided, created, or destroyed.
4. atoms of different elements combine in simple whole-number ratios to form chemical compounds
5. in chemical reactions, atoms are combined, separated, or rearranged
because atoms are electrically neutral....
... the must contain a positive charge to balance the negative electrons.
because electrons have so much less mass than atoms...
... atoms must contain other particles to account for their mass