Chapter 3: Atoms Flashcards
atom
fundamental unit of matter
Democritus
Greek philosopher who suggested that matter is make up of “indivisible” particles called atoms
Antoine Lavoisier
French chemist who observed that the total mass before and after a chemical reaction is the same, or the law of conservation of mass
John Dalton
English chemist who introduced the atomic theory
atomic theory
a scientific explanation for the nature of matter and chemical reactions
according to the atomic theory, elements are made up of
tiny, indivisible particles called atoms
according to the atomic theory, the atoms of each element are
unique; atoms of different elements are different
according to the atomic theory, atoms can join together in whole-number ratios to form
compounds
according to the atomic theory, atoms are ________ in chemical reactions
unchanged
Dimitri Mendeleev
Russian scientist who organized the known elements into a table based on their atomic masses and arranged elements with similar properties into columns
periods
horizontal rows on the periodic table
in a period, all elements have the same
number of electron shells
the next element in a period has one more
proton; it is less metallic than its predecessor
groups
columns on the periodic table
in a group, elements have similar
chemical properties and the same number of valence electrons
main-group elements
the left and right-hand blocks of the periodic table
transition metals
elements in the middle of the periodic table; tend to be harder and less reactive than the metals in the first two columns
inner transition elements
the two additional rows at the bottom of the periodic table
the first row of the inner transition elements is called the
lanthanide series; it contains heavier, naturally occuring metals called rare earth metals
the second row of the inner transition elements is called the
actinide series; the first few elements (up to uranium) are naturally occuring and the elements after are mostly human-made
metals
elements that are solid at room temperature, malleable, and conduct heat and electricity
nonmetals
elements found on the upper right side of the periodic table; physical properties vary widely
opposite of metals
metalloids
elements in a stairstep pattern between metals and nonmetals; are semi-conductors
alkali metals
elements that lie on the far left of the periodic table in column 1A; they are soft metals that react violently with air or moisture
alkaline earth metals
elements in column 2A that are also reactive but not as much as alkali metals; they react slowly with water and burn brightly when combined with oxygen
halogens
elements in column 7A that exist as diatomic molecules in their elemental form; they react quickly with metals and other nonmetals to form different compounds
noble gases
elements in column 8A that are stable and do not react with other elements to form compounds; they are gases at room temperature
nucleus
tiny, dense center of an atom
subatomic particles
smaller components of an atom - protons, neutrons, and electrons
proton
positively charged particle located in the nucleus with a mass of 1.0073 u
electron
negatively charged subatomic particle with a mass of 0.0005 u
neutron
neutral subatomic particle in the nucleus with a mass of 1.0087 u
J.J. Thomson
English physicist credited with the discovery of the electron; assumed that atoms must also contain positive charges to balance the negative charge
Plum Pudding model
model of J.J. Thomson’s theory; hypothesized that electrons were spread throughout a positive atomic substance the way blueberries are scatteried in a muffin
atomic number (Z)
the number of protons in an atom
mass number
the sum of the number of protons and neutrons in an atom
isotopes
atoms that have the same atomic number but have different mass numbers
in an isotope, the mass number is written at the
upper left-hand side of the chemical symbol; the atomic number is written at the lower left-hand side
Bohr model
atomic structure model consisting of the nucleus in the center and electrons surrounding it in orbits
quantum model
modern description of electronic behavior; electrons behave both as particles and waves
because electrons occupy the outer volume of the atom, they can
sometimes lose or pick up electrons from neighboring atoms to form ions
