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Study Guide for Chapter 3
If each atom of element D has 3 mass units and each atom of element E has 5 mass units, a molecule
composed of one atom each of D and E has
8 amu
In oxides of nitrogen, such as N2O, NO, NO2, and N2O3, atoms combine in small whole-number ratios.
This evidence supports the law of
Law of multiple proportions
Oxygen can combine with carbon to form two compounds, carbon monoxide and carbon dioxide. The
ratio of the masses of oxygen that combine with a given mass of carbon is 1:2. This is an example of
Law of definite proportions
According to the law of conservation of mass, when sodium, hydrogen, and oxygen react to form a
compound, the mass of the compound is ____ the sum of the masses of the individual elements.
equal to
The principles of atomic theory recognized today were conceived by
Dalton
Dalton's atomic theory agrees with modern atomic theory except for the statement that
all atoms of the same element have the same mass
Because any element used in the cathode produced electrons, scientists concluded that
all elements contained electrons
Whose series of experiments identified the nucleus of the atom?
Rutherford
Because most particles fired at metal foil passed straight through, Rutherford concluded that
most of the atom was empty space
Because a few alpha particles bounced back from the foil, Rutherford concluded that they were
there was a nucleus at the center of the atom
A nuclear particle that has about the same mass as a proton, but with no electrical charge, is called a(n)
neutron
An atom is electrically neutral because
the protons and electrons are equal
The smallest unit of an element that can exist either alone or in combination with other such particles of
the same or different elements is the
atom
Isotopes are atoms of the same element that have different
masses
All isotopes of hydrogen contain
one proton
The atomic number of oxygen, 8, indicates that there are eight
protons
The total number of protons and neutrons in the nucleus of an atom is its
mass number
All atoms of the same element have the same
atomic number
Atoms of the same element can differ in
mass
An aluminum isotope consists of 13 protons, 13 electrons, and 14 neutrons. Its mass number is
27
Chlorine has atomic number 17 and mass number 35. It has
17 protons, 17 electrons and 18 neutrons
Neon-22 contains 12 neutrons. It also contains
10 protons
The number of atoms in 1 mol of carbon is
6.022 x 1023
To determine the molar mass of an element, one must know the element's
atomic mass
Avogadro's number is
the number of particles in one mole of an element
What is the law of conservation of mass?
mass is neither created or destroyed
Give the location and relative charge of a proton.
in the nucleus and positive
The nucleus of an atom has all of the following characteristics except that it
it takes up most of the volume of the atom
The radius of an atom extends to the outer edge of the
electron cloud
The average atomic mass of an element is the average of the atomic masses of its
isotopes
As the atomic number increases, the number of electrons in a neutral atom
increases
What is an isotope?
an atom of the same element with different masses
Define the law of definite proportions, the law of conservation of mass, and the law of multiple
proportions.
State the 3 definitions
Why do scientists use Dalton's theory, even though parts of it have been proven wrong? How much of
Dalton's theory do scientists still accept?
Dalton started the foundation for the atomic theory. Parts of his theory are still true, everything is
made up of atoms and atoms cannot be created pr destroyed.