Chemistry Ch. 3

Front 1

size of an atom?

Back 1

40-270 pm

Front 2

size of nuclei

Back 2

0.001 pm

Front 3

atoms of the same element with different masses, due to the differences in the number of neutrons, are called

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isotopes

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the average atomic masses ont he periodic table include

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the masses of an atom's isotopes

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most common type of hydrogen isotope is called

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protium (99.985 % abundant)

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second most common type of hydrogen isotope

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deuterium (0.015% abundant)

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3rd most common type of hydrogen isotope

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tritium (radioactive)

Front 8

isotopes are identified by - -

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mass number

Front 9

to calculate the number of netrons:

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mass number - atomic number = neutrons

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can an atom have just any number of heutrons? (siotopes)

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no, there are preferred neutron-to-proton combinations (ratios) at which the forces holding the nuclei together seem to balance best

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- elements tend to have about as many neutrons as protons

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lighter

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- elements tend to need more neutrons than protons in order to stick together

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heavier

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atoms with too few many neutrons or not enough neutrons can sometimes exist for a while, but they're

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unstable

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unstable atoms are - so they decay and give off - in the form of particles and electromagnetic waves

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radioactive; radiation

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why don't protons repel each other int he nucleus since they have the same charge?

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whenever two protons are very close, there is actually a strong attractive (same situation exists for the closeness betwene protons and neutrons or between neutrons). these strong forces are called nuclear forces

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whenever two protons are very close, there is a strong attractive called

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nuclear forces

Front 17

top number on the periodic table is

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atomic number (number of protons)

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bottom number on the periodic table is

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the average atomic mass which is the average mass of all the isotopes of a particular atom

Front 19

how much does a proton weigh?

Back 19

1.673^-24 g x 6.02 x 1023 amu/1g = 1.007146 amu = 1 amu

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a proton is -x greater in mass than an electron

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1836x

Front 21

how much does a nuetron weigh?

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1.675 x 10^-24 g x 6.02 x 10^23 amu / 1g = 1.00835 amu = 1 amu

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a neutron is slightly - than a proton

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larger

Front 23

how much does an electron weigh?

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9.10 x 10^-28 x 6.02 x 10^23 amu/ 1g = 5.4782 x 10^-4 amu = 0amu

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an electron is - xs smaller than a proton

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1836

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1 - atom has a mass of 12 amu

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C-12

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when the atomic mass of an element is measured on an atomic mass scale, call it

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the relative atomic mass

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relative atomic mass is the mass of an atom as it compares with the mass of the atom

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C-12

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protons and neutrons don't have the mass in all elements due to the

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presence of isotopes

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when protons and neutrons come together to make the nucleus some mass is converted to energy, so some mass appears lost or missed but acutally

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mass is just converted to energy

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mass converted to energy is called

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nuclear binding energy

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energy is produced by

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building nuclei

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energy is also produced in

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destroying nuclei-fission

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the weighted average of atomic masses of the naturally occurring isotopes of an element

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average atomic mass

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calculated by considering the percent abundance of all the isotopes of that element and the mass of that isotope

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average atomic mass

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a unit of measurement - the amount of a substance that contains as many particles in exactly 12 g of carbon-12

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mole

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the number of particles in 12g of carbon has been determined experimentally to be

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6.02 x 10^23

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avogadro's number

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6.02 x 10^23

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there are - particles in 1 mol of a substance

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6.02 x 10^23

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the word "particle" can be defined as - in elements

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atoms

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the word "particle" can be defined as - in covalent compounds

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molecules

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the word "particle" can be defined as - - in ionic compounds

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formula units

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the mass of 1 mol of a pure substance (element or cpd) expressed in "g/mol" is numerically equal to:

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the atomic mass of the element in amu

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how do you find the molar mass of compounds?

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molar mass are found by adding the atomic masses of all the atoms in the formula

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conversions can be made using:

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moles, Avogadro's Number, and molar mass

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person who created the law of conservation of mass

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antoine lavoisier

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this law states that "mass is neither created nor destroyed during ordinary chemical reactions or physical changes

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law of conservation of mass

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person who created hthe law of definite proportions

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joseph proust

Front 48

this law states that a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or the source of the compound

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law of definite proportions

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person attributed for law of multiple proportions

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john dalton

Front 50

this law states that if two elements form multiple compounds, then the ratio of the masses of the second element, formed with a fixed mass of the first element, is always a small whole number

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law of multiple proportions

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all elements are composed of extremely small particles called

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atoms

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- studied the cathode ray experiments of other scientists which lead him to the discovery fo the electron

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JJ Thompson

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from experiments, Thompson discovered the ray contained mass through - - experiment

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paddle wheel experiment

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charge-to-mass ratio

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charge = 1.76 x 10^11 C/kg (coulombs per kilogram)

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atom is what charge?

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neutral

Front 56

in the plum pudding model, the plum pudding symbolized the - and the raisins symbolized -

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protons and electrons

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- coined the term "electron" to describe a negatively charged particle

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Stoney

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- used Thompson's calculation and his own "oil drop experiment" to determine the mass of an electron

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Robert Millikan

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Millikan found (the charge of an electron):

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-1.76 x 10^8 C/g x 9.11 x 10^-28 = -1.60 x 10^-19 C

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- believed that the positive charge in a nucleus was evenly distributed through out the atom and conducted experiements to test this hypothesis

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Rutherford

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from the - - experiment, Rutherford predicted that the atomic model was a planetery model (which was eventually proven wrong)

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gold foil experiment