Chem pretest- Atomic structure
if an atom of an element has a mass number of 32 and 20 neutrons in its nucleus, what is the atomic number of the element
12
in the nucleus of an atom there are 18 protons and 20 neutrons, what is the atomic number
18
in the nucleus of an atom there are 18 protons and 20 neutrons, what is the mass number
38
if an atom of tin has a mass number of 118 and an atomic number of 50, how many neutrons are in its nucleus
68
if an atom has 34 protons and 40 neutrons, what is its mass number
74
which statement about subatomic particles is true
An electron has far less mass than either a proton or neutron
according to ________ all matter was made up of four elements- earth, air, fire, and water
Aristotle
The greek philosopher democritus coined what word for a tiny piece of matter that cannot be divided
Atom
what did democritus believe about matter
Matter was made of tiny particles called atoms that could not be divided.
which of the following most accurately represents john daltons model of the atom
a tiny, solid sphere with a predictable mass for a given element
in rutherford's gold foil experiment, some of the __________ aimed at gold atoms bounced back, suggesting that a solid mass was at the center of the atom
alpha particles
which statement about electrons and atomic orbitals is NOT true
an electron had the same amount of energy in all orbitals
the number of protons in one atom of an element is that elements
atomic number
to find the number of neutrons in an atom, you would subtract
atomic number from mass number
Unlike Democritus, Aristotle did not believe that matter was composed of tiny, indivisible ________
atoms
which of the following is NOT part of john daltons atomic theory
atoms contain subatomic particles
The moving blades of an airplane propeller provide an analogy for the electron ____ model.
cloud
John Dalton observed that elements always combine in the same ratio to form a particular ________
compound
In an atomic model that includes a nucleus, positive charge is
concentrated at the center of an atom
JJ thomsons experiments provided evidence that an atom
contains negatively charged particle
Which subatomic particle has a negative charge?
electron
in bohrs model of the atom, ________ move in fixed orbits around the nucleus
electrons
which statement accurately represents the arrangement of electrons in bohr's atomic model?
electrons travel around the nucleus in fixed energy levels with energies that vary from level to level
John Dalton concluded that all the atoms of a single _____ have the same mass.
element
Who provided evidence for the existence of a nucleus in an atom?
ernest rutherford
which statement best describes rutherford's model of the atom
it is like a huge stadium with a positively charged marble at the center
in niels bohr's model of the atom, electrons move
like planets orbiting the sun
the ___________ of an isotope is the sum of the number of protons and neutrons in its nucleus
mass number
the subatomic particle that jj thomson discovered has a _________ charge
negative
the difference between a sample of heavy water and regular water is that a hydrogen atom in heavy water has an extra _______
neutron
Protons and ____________________ are found in the nucleus of an atom.
neutrons
The nuclei of isotopes contain different numbers of
neutrons
Alpha particle that bounce straight back from the foil have struck ________ in gold atoms
nuclei
What causes some of the alpha particles to bounce straight back from the gold foil
nuclei in the gold atoms
The results of Rutherford's gold foil experiment demonstrated that the __________ occupies a very small amount of the total space inside an atom.
nucleus
The region in which an electron is most likely to be found is called an _________
orbital
Nuetrons and _____ have almost the same mass
protons
which statement about subatomic particles is NOT true
protons and neutrons have the same charge
Democritus thought that matter was made of tiny particles
that could not be divided
what is the difference between an atom in the ground state and an atom in an excited state
the atom in an excited state has more energy and is less stable than the atom in the ground state
What can you assume has happened if an electron moves to a higher energy level?
the electron has gained energy
what does the electron cloud model descirbe
the most likely locations of electrons in atoms
which of the following is unique for any given element
the number of protons
Suppose an atom has a mass number of 23. Which statement is true beyond any doubt?
the number of protons in the nucleus does not equal the number of neutrons
According to John Dalton's observations, when elements combine in a compound,
the ratio of their masses is always the same
rutherfords gold foil experiment provided evidence for which of the following statements
there is a dense, positive charged mass in the center of an atom
which statement is true about oxygen-17 and oxygen-18
they are isotopes of oxygen