ATOMS, MOLECULES, AND IONS Flashcards
proposed the concept of fire, air, water, and earth to explain the composition of matter.
Empedocles (490-435 B.C.)
proposed the existence of a fifth element which he called quintessence.
Aristotle (384-323 B.C)
came up with a theory stating that everything is composed of small indivisible particles which he called atomos.
Democritus (460-370 B.C.)
____ proposed that atoms have fixed weights and definite properties.
John Dalton
’ experiment about the cathode rays helped English physicist
Sir William Crookes
_____ discover the electron in 1897
J.J. Thomson
_____ determined the charge of an electron in 1909.
Robert Millikan
_____ gold-foil experiment helped him elucidate the existence of the nucleus.
Ernest Rutherford’s
_____ suggested that the total energy of an electron is quantized.
Niels Bohr
The _______ of mass states that the mass of the products in a chemical reaction will always be equal to the mass of the reactants.
law of conservation
The ______ states that all the samples of a chemical compound contain all the elements in the same proportion.
law of constant composition
The ________ states that the elements in a compound have a proportion of those chemical compounds that can be expressed in a small, whole-number ratio.
law of multiple proportions
An ____ is a small, indivisible particle considered as the basic unit of matter.
atom
____ are positively-charged particles located inside the nucleus.
Protons
_____ are small, negatively-charged particles that spin around the nucleus.
Electrons
____ have no charge and are also located inside the nucleus.
Neutrons
The _______ is equal to the number of protons inside the nucleus.
atomic number (Z)
The _________ is the sum of the number of protons and the number of neutrons in the nucleus.
mass number (A)
_____ are kinds of the same element that have the same number of protons, but different numbers of neutrons.
Isotopes
_____ of an element have the same atomic number but different mass numbers.
isotopes
_________ uses special X-rays to obtain images from different angles of the body.
Computed Axial Tomography (CT Scan)
uses a strong magnetic field and radiofrequency waves, also providing cross-sectional images that allow doctor to diagnose diseases inside the body.
Magnetic Resonance Imaging (MRI) MRI
______$ is a new experimental cancer therapy which selectively destroys cancerous tissues without harming the healthy surrounding cells.
Boron Neutron Capture Therapy (BCNT)
_____ are atoms that are chemically bonded together.
Molecules
Molecules can occur in nature as ____ or ___.
diatomic ; polyatomic
A ____ molecule contains only two atoms
diatomic
A ____ molecule contains three or more atoms.
polyatomic
____ are atoms or molecules that have a charge, meaning, the number of protons is not equal to the number of electrons, giving the atom either a positive or a negative net charge.
lons
A _____ formula is a way of expressing the elements present in a compound in symbols, as well as the number of atoms of each element present in the compound.
chemical
A _____ formula is a graphical representation of the compound using the symbol of the elements to indicate how the atoms are arranged and bonded chemically.
structural
A _____ formula is a formula that shows the atoms present in a compound, as well as the number of atoms per element present in it.
molecular
An _____ formula is a formula that shows the simplest form of the atomic ratio in a chemical compound.
empirical
A ___ is a representation of a compound’s molecular structure.
model
A _____ model depicts the 3-dimensional view of the atoms of a compound and the bonds between them.
ball-and-stick
• A ____ model depicts the atoms of the compound using spheres that are joined together, approximating the actual sizes of the atoms.
space-filling
An ionic compound is a ____ compound that contains a cation and ananion.
neutrally-charged
A _______ is made up of only one atom.
monoatomic ion
A _____ ion is made up of more than one atom of different elements
polyatomic
A _____ compound is composed of nonmetallic elements
molecular
