CHEM 105 Chapter 1 Quiz Flashcards
atoms
basic submicroscopic particles that constitute the fundamental building blocks of ordinary matter
molecules
substances formed when two or more atoms come together (bond) in specific geometric arrangements
? determine how matter behaves
atoms and molecules
matter can be classified according to ? and ?
its state (physical form) and its composition (the types of particles)
matter can be classified into ? or ? depending on if it has one type of particle or not
a pure substance (one type of particle) or a mixture (more than one)
a pure substance can be classified into ? or ? depending on if it is separable into simpler substances
element (not separable, e.g. Helium) and compound (separable, e.g. H2O)
a mixture can be classified into ? or ? depending on whether or not it is uniform throughout
heterogeneous (not uniform, e.g. wet sand) and homogeneous (uniform, e.g. tea with sugar)
element
a substance that cannot be chemically broken down into simpler substances
compound
a substance composed of two or more elements in fixed definite proportions
key characteristics of the scientific method
observations, formulation of hypothesis, experimentation, formulation of laws and theories
observations
descriptions about characteristics/behavior of nature
hypothesis
a tentative interpretation or explanation of the observations
a good hypothesis is ?, meaning ?
falsifiable: able to be proved wrong
a scientific law
a brief statement that summarizes past observations and predicts future ones
theory
a well-established hypothesis or set of hypotheses form the basis for a scientific theory; tries to explain not merely what nature does, but why a natural phenomenon happens; validated by experimental results but can never be conclusively proven
qualifiable data
observational, subjective in nature (e.g. color, shape)
quantifiable data
measurable (empirical), objective in nature; uses equipment capable of generating empirical data with standardized units
Dalton’s atomic theory
- each element is composed of tiny, indestructible particles called atoms
- all atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements
- atoms combine in simple, whole-number ratios to form compounds
- atoms of one element cannot change into atoms of another element; in a chemical reaction, atoms change only the way that they are bound together with other atoms
the law of conservation of mass
in a chemical reaction, matter is neither created nor destroyed
the law of definite proportions (Joseph Proust)
all samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements
the law of multiple proportions (John Dalton)
when two elements (call them A and B) form two different compounds, the masses of element B that combine with one gram of element A can be expressed as a ratio of small whole numbers
the discovery of the electron (JJ Thompson’s cathode ray experiment)
Thompson was able to measure the charge-to-mass ratio of cathode ray particles by deflecting them using electric and magnetic fields, which are electrons
the charge-to-mass value of the electron as measured by JJ Thompson
-1.76 x 10^8 coulombs per gram
determining the charge of the electron (Robert Millikan’s oil drop experiment)
determined the mass of oil drops from their radii and density; the charge of any oil drop was always a whole number multiple of -1.60 x 10^-19 C
the fundamental charge of a single electron
-1.60 x 10^-19 C
JJ Thompson’s model
plum pudding: the negatively charged electrons were small particles held within a positively charged sphere
conclusions of Rutherford’s gold foil experiment
some particles were deflected, so matter must not be as uniform as it appears; it must contain large regions of empty space dotted with small regions of very dense matter (nuclear model)
nuclear theory of the atom
- most of the atom’s mass and all of its charge are contained in a small core called a nucleus
- most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed
- there are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons) in side in the nucleus, so that the atom is electrically neutral
Rutherford’s student ? demonstrated that the previously unaccounted for mass in the nucleus was due to ?
James Chadwick; neutrons
the mass of the ? and the ? are the most similar
proton and neutron
the charge of the ? and ? are the most similar
proton and electron, though they have opposite signs
the most important number to the identity of an atom is ?
Z, its atomic number (the number of protons in its nucleus)
isotopes
all atoms of a given element have the same number of protons, but not necessary the same number of neutrons
the sum of the ? and ? in an atom is its mass number, represented by the symbol A
protons and neutrons
the notation for an isotope is either ? or ?
X (the chemical symbol) with its mass number (A) to the top left and its atomic number (Z) to the bottom left of it
or
the chemical symbol (X) or name, hyphen, mass number (A) [e.g. Ne-20 or neon-20]
natural abundance
the relative amount of each different isotope in a naturally occurring sample of a given element is roughly constant; these % are called the natural abundance of the isotopes
ions
in chemical changes, atoms can lose or gain electrons and become charged particles called ions
cations
positively charged ions
anions
negatively charged ions
atomic mass
the average mass of the isotopes that compose that element; calculated by the sum of each (fraction of isotope n) * (mass of isotope n), with the fraction being the decimal value of the natural abundance % and the mass being the mass number of the isotope
mass spectrometry
the masses of atoms and the % abundance of isotopes of elements are measured using this technique
1 mol
6.022 x 10^23 atoms
