unit 2 chem test
law of definite proportions example
10 g water----- 8.9 oxygen, 1.1 hydrogen----- 8:1 ratio ALWAYS
what does the pt help determine?
???
is there a particle whose number cannot be determined solely from the pt?
????? (yes neutrons... need mass number....)
to what does the term periodic in periodic table refer?
a repeating pattern of similar properties
list the 2 conclusions rutherford reached after conduction experiment. what evidence from gold foil experiment backs up these claims?
a.) most of atom composed of empty space evidence: most alpha particles traveled through foil to back of deflection screen b.) small, dense positive charge mass at center of atom evidence: some particles bounced/ deflected toward box in experiment
how do ions form?
adding or losing electrons
group 1
alkali metals
group 2
alkaline earth metals
in general do nonmetals from cations or anions?
anions
how can we use the pt to determine the number of subatomic particles in a neutral atom?
atomic # = protons and electrons
how were early pt organized?
atomic mass
what points in dalton's theory best explain each of the 3 laws and how?
atoms cannot be destroyed or divided- law of conservation of mass atoms can combine chemically in whole number ratios- law of multiple proportions OR law of definite proportions
what are isotopes?
atoms that have same number of protons but different number of neutrons (same physical and chemical properties)
what were democritus's ideas about atoms?
atoms were indivisible and indestructible
how did the experiments with the crookes tube show that electrons have a negative charge?
attracted to positively charged metal
what was dalton attempting to do with his theory?
back up democritus's theory with evidence
why did rutherford believe an alpha particle would travel straight through the gold foil?
bc alpha particles are very big compared to electron and the electrons would not deflect alpha particles bc they are so large
where does the atomic number of an isotope appear in the nuclide symbol?
bottom left corner
law of multiple proportions example
carbon and oxygen----- carbon monoxide and carbon dioxide
in general, do metals from cations or anions?
cations
what made dalton different from democritus?
dalton was a scientist bc he used evidence
how are isotopes of the same element different from each other?
different mass numbers (not same number of neutrons)
law of conservation of mass example
dissolving salt, melting ice
properties of nonmetals
dull, snap or shatter when bent/pulled, do not conduct, are insulators
what did millikan measure about the electron?
exact charge
how does the crookes tube work?
gas at a low pressure, electrodes attached to each end of tube, voltage is applied, beam travels from cathode (positive) to anode (negative)
group 17
halogens
how are millikan's experiments and results significant to atomic theory?
his results counteract w/ atomic theory and say that atoms are divisible! (electron is a particle smaller than the smallest known atom)
which elements exist naturally as diatomic elements?
hydrogen nitrogen oxygen fluorine chlorine bromine iodine (written like H2, N2...)
law of definite proportions
in chemical compound, masses of the same element are always present in the same proportion no matter the size
how is the current pt organized?
increasing atomic number
properties of metals
luster, ductile, malleable, conduct electricity
what was millikan about to calculate about the electron?
mass
law of conservation of mass
mass neither created nor destroyed in a chemical or physical reaction
according to millikan's findings, how does the mass of the electron compare to the mass of the lightest known atom (hydrogen)?
mass of electron is 1000 times smaller than hydrogen
what does the stair-step line on the pt tell you?
metalloids/ distinguish metals from nonmetals
how does the size of the atomic nucleus compare to the size of the space occupied by the electrons in an atom?
most of the mass of the atom is found in nucleus (protons and neutrons) most of the volume is found in electron cloud
did the oil drop experiment change the plum pudding model of the atom? why?
no
was democritus a scientist?
no bc he had no experimental evidence
are all atoms of a single element identical?
no, always have same number of protons but may have different number of neutrons
are neutral atoms of the same element alike? why?
no, different number of neutrons
group 18
noble gases
what can we predict using the pt?
properties of an element
properties of metalloids
properties of both metals and nonmetals
how is the mass number of an isotope calculated?
protons + neutrons
law of multiple proportions
same 2 elements can form more than 1 compound
how are isotopes of the same element alike?
same atomic number (protons)
why does an atom have a zero net charge?
same number of protons and electrons... balance eachother
why are the elements in the vertical groups called families or groups?
similar behavior/ chemical properties
what are the relationships between the group number on the pt and the types of ions formed?
starting with group 1, plus 1 charge (1+).... group 2, plus 2 charge (2+), groups 3-12- not determined easily... group 17- minus 1 charge (1-), group 18- no charge
how did experiments with the crookes tube show that electrons are part of all matter?
the cathode ray was deflected to a magnetic field
what was rutherford trying to test with the gold foil experiment?
thomson's model of the atom
where does the mass number of an isotope appear in the nuclide symbol?
top left corner
groups 3-12
transition metals
in the oil drop experiment, how was millikan able to cause electrons to jump off the air molecules and onto the oil droplets?
x-ray source
did the crookes tube experiment change the atom? why?
yes, showed that the atom is neutral & electrons in a sphere of protons. (plum pudding)
