Atoms Flashcards
He believed that all matter is made of very
small particles—much too small to see.
Democritus
The small particles that made up the matter is called
Atoms
Greek word of atom
Atomos
Atomos meaning
not to cut
They did not believe in atoms at all.
They insisted that matter is infinitely divisible.
Zeno of Elea
It is a substance (for example, carbon, hydrogen, and iron) that
consists of identical atoms.
Element
Number of elements occur in nature
88
It is a pure substance made up of two or more elements in a
fixed ratio by mass.
Compound
The big four elements
Carbon, Hydrogen, Oxygen, Nitrogen
It is a pure substance made up of two or more elements in a
fixed ratio by mass.
mixture
All matter is made up of very tiny, indivisible particles, which Dalton
called
atoms
is a tightly bound combination of two or more atoms that
acts as a single unit.
Molecule
He discovered the law of conservation of mass
Antoine Laurent Lavoisier
states that matter can be
neither created nor destroyed.
law of conservation of mass
which states that any compound is always
made up of elements in the same proportion by mass.
law of constant composition
He discovered the law of constant composition
Joseph Proust
consist of single atoms
that are not connected to each other
Monoatomic elements
Example of monoatomic elements
Helium and Neon
contains two atoms in
each molecule, connected to each other by a chemical bond.
Diatomic elements
Example of diatomic elements
H, N, F, Cl, Br, and I
Some elements have even more atoms in each molecule.
Polyatomic elements
Are referred to as polyatomic elements.
Diamond and S8
A subatomic particle with
a charge of 11 and a mass of
approximately 1 amu; it is found
in a nucleus.
Proton
A unit
of the scale of relative masses of
atoms: 1 amu = 1.6605x10^-24 g
Atomic mass unit
A subatomic particle
with a charge of 21 and a mass
of approximately 0.0005 amu. It is
found in the space surrounding a
nucleus.
Electron
A subatomic particle
with a mass of approximately
1 amu, and a charge of zero; it is found in the nucleus
Neutron
which is the sum of the number
of protons and neutrons in its nucleus.
Mass number
It is the number of protons in its nucleus.
Atomic number
Atoms with the same number of protons but
different numbers of neutrons are called
Isotopes
It is a weighted average of the masses (in amu) of its isotopes found on the Earth.
Atomic weight
A typical heavy atom (although not the heaviest) is
Lead-208
He produced one of the first periodic tables, the form of which we
still use today
Dmitri Mendeleev
Horizontal rows of periodic table
Periods
Vertical columns of periodic table
Groups
Chlorine, Bromine, Iodine
Halogens
They are solids (except for mercury, which is a liquid), shiny, conductors of electricity, ductile (they can be drawn into wires), and malleable (they can be hammered and rolled into sheets).
Metals
Second class of elements
Nonmetals
These elements have some properties of
metals and some properties of nonmetals.
Metalloids
He said that only certain values of kinetic energy of electrons are possible (energy levels); values in between are not permitted
Neils Bohr
He said that electrons in atoms do not move freely in space around nucleus; confined to specific regions called principal energy levels/ shells
Neils Bohr
The lowest possible energy
level is the
Ground state
electrons in atoms do not move freely in the space around the nucleus, but rather are confined to specific regions of space called
Principal energy level = shells
Shells are divided into
Subshells
region of space and can hold two electrons
orbitals
is a description of the orbitals that
its electrons occupy.
Electron configuration
Outer-shell electrons are
called
Valence electrons
energy level in which valence electrons are found is
called the
Valence shell
To show the outermost electrons of an atom, we commonly use a representation called
Lewis dot structure
Lewis dot structure is named after
Gilbert N. Lewis
It shows the symbol of the element surrounded by a number of dots equal to
the number of electrons in the outer shell of an atom of that element.
Lewis Structure
It is a measure of how difficult it is to remove the
most loosely held electron from an atom in the gaseous state.
Ionization energy
It involves only the separation, combination, or rearrangement
of atoms; it does not result in their creation or destruction.
Chemical reaction
States that different samples of the
same compound always contain its constituent elements in the same proportion by mass
Law of definite proportions
if two elements can combine to form more than one und, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers
Law of multiple proportions
the emission and transmission of energy through space in the form of waves.
Radiation
Negatively charged plate
Cathode
positively charged plate
Anode
He noticed that cathode rays caused glass
and metals to emit very unusual rays.
Wilhelm Roentgen
He found that exposing thickly wrapped photographic plates to a certain uranium compound caused them to darken, even without the stimulation of cathode rays
Antoine Becquerel
spontaneous emission of particles and/or radiation
Radioactivity
spontaneous emission of particles and/or radiation
Radioactive
Suggested the name radioactivity
Marie Curie
consist of positively charged particles
Alpha particles
electrons and are deflected by the negatively charged plate
Beta particles
type of radioactive radiation consists of high-energy rays called
Gamma rays
He determined the charge of electron
Robert Andrews Millikan
He investigated the structure of the
atomic nucleus.
Ernest Rutherford
HE focused on the structure of the atomic nucleus and on radioactivity.
Johannes Hans Wilhelm Geiger
A device for measuring radiation that is now commonly called the
Geiger counter
He proved the existence
of neutrons
James Chadwick
an ion with a net positive charge
Cation
an ion whose net charge is negative due to an increase in the number of electrons.
Anion
It is formed from cations and anions
Ionic compound
Used to express the composition of molecules and ionic compounds in terms of chemical symbols.
Chemical formulas
shows the exact number of atoms of each element in the smallest unit of a substance
Molecular formula
one of two or more distinct forms of an element.
Allotrope
It tells us which elements are present and the simplest whole-number ratio of their atoms
Empirical formula
compounds formed from just
two elements.
Binary compounds
compounds consisting of three elements.
Tertiary compounds
can be described as a substance that yields hydrogen ions (H+) when dissolved
in water.
Acid
are acids that contain hydrogen, oxygen, and another element (the central element). T
Oxoacids
can be described as a substance that yields hydroxide ions (OH-) when dissolved in water
Base
discovered that atoms and molecules emit energy only in certain discrete quantities, or quanta
Max Planck
a vibrating disturbance by which energy is transmitted
wave
the distance between identical points on successive waves
wavelength
number of waves that pass through a particular point in one second
frequency
vertical distance from the midline of a wave to the peak or trough.
amplitude
proposed that visible light consists of electromagnetic waves
James Maxwell
has an electric field component and a magnetic field component
electromagnetic wave
the emission and transmission of energy in the form of electromagnetic waves
electromagnetic radiation
the smallest quantity of energy that can be
emitted (or absorbed) in the form of electromagnetic radiation
quantum
the smallest quantity of energy that can be
emitted (or absorbed) in the form of electromagnetic radiation.
photoelectric effect
photoelectric effect is also called
threshold frequency
particles of light
photons
either continuous or line spectra of radiation emitted by substances
emission spectra
the light emission only at specific wavelengths
line spectra
the lowest energy state of a system
ground state
higher in energy than the ground state
excited state
he proposed that matter and radiation have the properties of both wave and particle
Louis de Broglie
it is impossible to know simultaneously both the momentum p (defined as mass times velocity) and the position of a particle with certainty
Heisenberg uncertainty principle
specifies the possible energy states the electron can occupy in a hydrogen atom and identifies the corresponding wave functions
Schrodinger equation
gives the probability that an electron will be found in a particular region of an atom
electron density
the wave function of an electron in an atom
atomic orbital
describe the distribution of electrons in hydrogen and other atom
quantum numbers
determines the energy of an orbital
principal quantum number
tells us the “shape” of the orbitals
angular momentum quantum number
A collection of orbitals with the same value of n is frequently called a
shell
describes the orientation of the orbital in space
magnetic quantum number
To take the electron spin into account, it is necessary to introduce a fourth quantum number
electron spin quantum number
encloses about 90 percent of the total electron density in an orbital
boundary surface diagram
encloses about 90 percent of the total electron density in an orbital
electron configuration
no two electrons in an atom can have the same
four quantum numbers
Pauli exclusion principle
are attracted by a magnet
Paramagnetic substances
are slightly repelled by a magnet
Diamagnetic
the most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins
Hund’s rule
as protons are added one by one to the nucleus to build up the elements, electrons are similarly added to the atomic orbitals
Aufbau principle
the minimum energy (in kJ/mol) required to remove an electron from a gaseous atom in its ground state
Ionization energy
the radius of a cation or an anion
Ionic radius
the energy change that occurs when an electron is accepted by an atom in the gaseous
state to form an anion
Electron affinity
