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flashcards from the unit 2 crossword Baker gave us.


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

molar mass

the mass in grams of 1 mol of a substance


the smallest unit of an element that maintains the chemical properties of that element

quantum theory

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.

electromagnetic radiation

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

continuous spectrum

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 basic unit of electromagnetic energy; it characterizes the wave properties of electrons

Avogadro's number

6.02 x 10^23, the number of atoms or molecules in 1 mol


the distance from any point on a wave to an identical point on the next wave


the number of cycles or vibrations per unit of time; also the number of waves produced in a given amount of time

electromagnetic spectrum

all of the frequencies or wavelengths of electromagnetic radiation

excited state

a state in which an atom has more energy than it does at its ground state


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

mass number

the sum of the numbers of protons and neutrons in the nucleus of an atom

ground state

the lowest energy state of a quantized system


something that has magnitude, size, or amount

density formula


percentage error

PE=Value experimental- value accepted/value acceptedx100


the closeness of measurements to the correct or accepted value of the quantity measured


the closeness of a set of measurements of the same quantity made in the same way`

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

mass of an electron

0.109x 10^ -31

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

plum pudding model

negative electrons are spread evenly throughout the positive change of the rest of the atom

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