chem chapter 2 Flashcards
What did JJ Thomas discover?
Electrons
How did JJ Thomas discover electrons?
Beam from the cathode ray tube is deflected toward a positively charged plate.
plum pudding model
electrons are distributed throughout positively charged sphere
What did Robert Mullikan discover?
The mass and charge of an electron
How did Robert Mullikan discover the mass of electrons?
His oil drop experiment measured the electric charge of a single electron
What did Henri Becquerel discover?
Some materials produce invisible radiation, consisting of charged particles
What did Marie and Pierre Curie discover?
radiation consisted of small particles
Radioactivity:
Spontaneous emission of high energy radiation and particles
beta particles
high energy electrons
alpha particles
+2 charge
What did Ernest Rutherford do?
bombarded a thin gold foil with alpha particles to test the plum pudding model
What did James Chadwick do?
bombarded a thin sheet of beryllium with alpha particles and radiation was not deflected.
what did James Chadwick discover?
Neutrons
What did Francis Aston’s Positive Ray Analyzer do?
Neon gas ions of different masses strike the detector in different locations.
what were the results of the positive ray analyzer?
two different kinds of neon gas atoms exist: 90% is 20 amu; 10% is 22 amu
Isotopes
atoms of an element containing the same number of protons but different number of neutrons
Isotope symbol: Mass number
A: total number of nucleons in the nucleus
elemental symbol
one or two letter symbols to identify the type of atom
atomic number
Z; the number of protons only in the nucleus; identifies the element
average atomic mass
weighted average of the masses of all isotopes of an element
natural abundance
how much of each isotope is in a natural sample
What did Dmitri Mendeleev do?
ordered elements by atomic mass, columns based on chemical and physical properties, and left open spaces for elements undiscovered.
How is the periodic table organized?
horizontal rows are periods, vertical columns are groups
What categories are elements on periodic table divided into?
metals - left and bottom
non metals - right and top
metalloids - between metals and nonmetals
what are the groups of elements?
alkali metals, alkaline earth metals, halogens, noble gases
molecular compounds
atoms held together by covalent bonds
covalent bond
bond between two atoms created by sharing one or more pairs of electrons
what are molecular compounds composed of?
nonmetals
molecular formula
shows the number and type of atoms present in one molecule of a compound
empirical formula
smallest whole number ratio of elements in a compound
ionic compounds
consist of ions that formed due to the complete transfer of electrons.
what are ionic compounds made of?
a metal and a nonmetal
do metals and nonmetals for cations or anions?
metals form cations; nonmetals form anions
what are molecular compounds formed of?
nonmetals
how are molecular compounds named?
first words is the first element in the formula. second word is the second element with modified suffix. use prefixes to indicate number of atoms of each element. sulfur trioxide
