Chapter 2 Flashcards
Scanning tunneling microscopy (STM)
a technique that can image, and even move, individual atoms and molecules
tunneling current
the electrical current that flows between the tip of the electrode and the surface even though the two are not in physical contact
The smalles identifiable unit of an element
atom
the law of conservation of mass
In a chemical reaction, matter is neither created nor destroyed
Antoine Lavoisier formulated this law
the law of conservation of mass
Joseph Proust observed this law
The law of definite proportions
the law of definite proportions
All samples of a given compound, regardless of their source or how they are prepared, have the same proportions of their constituent elements
John Dalton stated this law
the law of multiple proportions
the law of multiple proportions
When two elements (A and B) form two different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers.
John Dalton stated this theory
atomic theory
Atomic theory
- each element is composed of tine, 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-numbered ratios to form compounds
- atoms of one element cannot change into atoms of another element.
J.J. Thompson used this to discover electrons
cathode rays in a cathode ray tube
electron
negatively charged, low mass partical present within all atoms
electrostatic forces
electrical charge is a fundamental property of some of the particles that compose atoms and results in attractive and repulsive forces
electric field
An area around a charged particle where electrostatic forces exist
J.J. Thompson discovered this
Electrons
Robert Millikan
discovered the charge of a single electron with his oil drop experiment
Electron charge
-1.60 x 10^-19 C
Electron mass
.00091 x 10^-27 kg
Radioactivity
the emission of small energetic particles from the core of certain unstable atoms
Henri Becquerel and Marie Curie discovered this
radioactivity
Rutherford proposed this
nuclear theory, after completing his gold foil experiment
nuclear theory states
- Most of the atom’s mass and all of its positive charge are contained in a small core called the nucleus
- most of the volume of the atom is empty space, throught which tine, negatively charged electrons are dispersed
- there are as many negatively charged electrons outside of the nucleus as there are positively charged particals withing the nucleus, so the atom is electrically neutral
neutrons
neutral particles withing the nucleus, with mass similar to a proton
James chadwick found these
neutrons
Atomic Mass Unit (AMU)
defined as 1/12 the mass of a carbon atom containing six protons and six neutrons
proton mass
1.672 x 10^-27 kg
proton charge
+1.602 x 10^-19 C
neutron mass
1.674 x 10^-27 kg
neutron charge
0
Defines an element
the number of protons
atomic number
the number of protons in an element
chemical symbol
one or two letter abbreviation listed directly below its atomic number
Elements chemical symbols and names come from
English names, latin names, names to reflect properties, and astronomical bodies, and scientist who discovered it
Isotope
Atoms with the same number of protons but different numbers of neutrons
Natural abundance
the percentage of the individual isotopes found in nature
mass number
the sum of the number of neurons and protons in an atom
Ions
When an atoms loses or gains and electron
Cation
positively charged ion
anion
negatively charged ion
Dmitri Mendeleev
created the periodic table, and stated the periodic law
periodic law
When elements are arranged in order of increasing mass, certain sets of properties recur periodically
Classifications of elements in the periodic table
metals, nonmetals, metalloids
metals
lie on the lower left side and middle of the periodic table and share some common properties. good conductors, malleability, ductility, often shiny, and tend to lose electrons when they undergo chemical changes
nonmetals
lie on the upper right side of the periodic table. varied properties(solid, liquid, gas), tend to be poor conductors, and they tend to gain electrons when they undergo chemical changes.
metalloids
lie alone the zigzag diagonal line that divides metals and nonmetals. exhibit mixed properties. some are classified as semiconductors
semiconductors
The classification for several metalloids, because of their intermediat and highly temperature dependent electrical conductivity. the ability to change and control conductivity makes them useful in making electronic chips and circuits.
main group elements
properties tend to be largely predictable based on their position in the periodic table. 1a-2a, 3a-8a
transition elements or transition metals
properties tend to be less predictable based on their position in the periodic table. 3b-8b, 1b-2b
family or group
each column within the main-group regions of the periodic table
Noble gasses
mostly unreactive, 8a
alkali metals
reactive metals, 1a
alkaline earth metals
fairly reactive, although not as reactive as alkali metals, 2a
halogens
very reactive nonmetals, 7a
Predicting ions (2 ways)
- main group metal tends to lose electrons, forming a cation with the same number of electrons as the nearest noble gas
- main group nonmetals tend to gain electrons, forming an anion with the same number of elctrons at the nearest noble gas
Atomic mass
calculation of the average mass of an element found by taking the percent natural abundance found of each isotope.
Mole
the amount of a material containing 6.022 x 10^23 particles
avogadros number
6.022 x10^23 particles,
How does the mole get its specific value
the value of the mole is equal to the number of atoms in exactly 12 grams of pure carbon-12
1 mole = (particles, grams)
6.022 x 10^23 particles, atomic mass # of grams
molar mass
an element’s molar mass in grams per mole is numerically equal to the element’s atomic mass in atomic mass units
