Atoms, Elements, And Periodic Table
What did Bohr's model of the atom include that Rutherford's model did not have?
((((NOT)))) smaller particles ((((NOT)))) a nucleus
Scientists have changed the model of the atom as they have gathered new evidence. One of the atomic models is shown below. What experimental evidence led to the development of this atomic model from the one before it?
(((NOT))) .A few of the positive particles aimed at a gold foil seemed to bounce back. (((NOT))) Equations were used to identify regions around the nucleus where electrons would likely be.
What is the mass of a neutron?
1 amu
What value is closest to the mass of the atom?
10 amu
One isotope of sodium has 11 protons and 7 neutrons. What is the mass number of this isotope?
18
All atoms of the element potassium have 19 protons. One of the most stable types of potassium atoms has the mass number 39. How many neutrons make up one of these potassium atoms?
20
An atom of the element chromium has an atomic number of 24 and a mass number of 52. How many electrons are in an uncharged atom of chromium?
24
The model below shows an atom of an element. What is the atomic number of this atom?
8
Scientists have changed the model of the atom as they have gathered new evidence. One of the atomic models is shown below. What experimental evidence led to the development of this atomic model from the one before it?
A few of the positive particles aimed at a gold foil seemed to bounce back.
Rutherford used positively charged particles to investigate the structure of the atom. The results surprised him, and he developed the atomic model shown below. What surprising result is explained using this model?
A few positive particles bounced back because they were pushed away from the positive center.
The charged particles in the beams that Thomson studied came from atoms. As these particles moved away from their original atoms, they formed a visible beam. The current model of the atom includes protons, neutrons, and electrons. What is the best use of an atomic model to explain the charge of the particles in Thomson's beams?
An atom's smaller negative particles are at a distance from the central positive particles, so the negative particles are easier to remove.
Which statement describes an atomic nucleus?
An atomic nucleus contains most of the atom's mass.
Which statements belong to Dalton's atomic theory? Select all that apply.
Atoms cannot be created or destroyed. Atoms cannot be broken down into smaller pieces. All atoms of an element are identical. Chemical reactions cause atoms to be rearranged.
Which statement best explains why the overall charge on an atom is zero?
B: The positive charge of the protons in the nucleus equals the negative charge in the electron cloud.
Who described atoms as having a positive nucleus with electrons that have different energies at different distances from the nucleus.
Bohr
____________________ described atoms as having a positive nucleus with electrons that have different energies at different distances from the nucleus.
Bohr
Oppositely charged objects attract each other. This attraction holds electrons in atoms and holds atoms to one another in many compounds. However, Ernest Rutherford's model of the atom failed to explain why electrons were not pulled into the atomic nucleus by this attraction. What change to the atomic model helped solve the problem seen in Rutherford's model?
Bohr's work with atomic spectra led him to say that the electrons were limited to existing in certain energy levels, like standing on the rungs of a ladder.
The chemical symbol for the element calcium is Ca. What would be the symbol representing calcium atoms that have lost two electrons?
Ca+2
Who described atoms as small spheres that could not be divided into anything smaller?
Dalton
Who first used the word "atomos" to describe the smallest unit of a substance?
Democritus
What did J.J. Thomson's experiments with cathode ray tubes imply about the mass of an electron?
Electrons are many thousand times smaller than the nucleus and negatively charged.
The modern model of the atom describes electrons in a little less specific detail than earlier models did. Why is it that being less sure about the placement of electrons in an atom is actually an improvement over earlier models?
Electrons do not follow specific paths, so describing the area where an electron is likely to be is more scientifically accurate.
Scientists have changed the model of the atom as they have gathered new evidence. One of the atomic models is shown below. What experimental evidence led to the development of this atomic model from the one before it?
Equations were used to identify regions around the nucleus where electrons would likely be.
The Venn diagram compares protons with neutrons. Which shared property belongs in the region marked "B"?
Has mass of 1 amu
Rutherford investigated atoms by firing small, positively charged particles at a thin sheet of gold foil. What results would he expect to see if he believed Thomson's model of the atom to be correct?
Most of the particles would pass through with a few moving at small angles because the atom was a low-density, positive material with electrons in it.
Particle A has very little mass in comparison to Particle B. Both particles are in the same atom. Which is the best conclusion about Particles A and B?
Particle A orbits the nucleus, and Particle B is located in the nucleus.
How does an atom change if all of its electrons are removed?
The atom becomes positively charged.
An atomic physicist determines that an atom is composed of 8 positively charged particles and has a mass of 15 amu. Which is the best conclusion that can be drawn?
The atom has 7 neutrons and 8 protons.
What did Ernest Rutherford expect to happen when he aimed a beam of particles at a thin gold foil?
The particles would be deflected slightly after passing through the foil.
Which statement best explains why the overall charge on an atom is zero?
The positive charge of the protons in the nucleus equals the negative charge in the electron cloud.
What is most likely true of an atom with a mass of 15 amu?
The total number of protons and neutrons is 15.
How does Rutherford's model of the atom compare with Thomson's model?
They both describe atoms as being made up of positive and negative matter.
What did Thomson's and Rutherford's experiments have in common?
They both used charged particles in their experiments.
Uranium is an element that is often used in nuclear power plants. Uranium atoms are very large, and the substance can be dangerous if it is not carefully contained. What is true about all uranium atoms?
They each have the same number of protons.
Who developed the first model of the atom that showed the structure of the inside of an atom?
Thomson
__________________ developed the first model of the atom that showed the structure of the inside of an atom.
Thomson
What discovery lead J.J. Thomson to decide that atoms were not indivisible, but are actually composed of smaller parts?
Thomson used a beam of negatively charged particles.
Based on the article "Will the real atomic model please stand up?," describe what Dalton's theory states about a molecule of water.
Water molecules are made of two different kinds of atoms. All water molecules have twice as many hydrogen atoms as oxygen atoms. All water molecules have one oxygen atom for every two hydrogen atoms.
Jerome is learning how the model of the atom has changed over time as new evidence was gathered. He has images of four models of the atom, but they are not in the correct order. In what order should Jerome put these models to show the development from the earliest model of the atom to the most recent one?
Y, X, Z, W
What did Rutherford's model of the atom include that Thomson's model did not have?
a nucleus
Atoms of two different elements must have different
atomic numbers
Using a cathode ray tube, Thomson confirmed that
atoms are made of particles that have a negative charge.
An atom's emission of light with a specific amount of energy confirms that
electrons emit and absorb energy based on their position around the nucleus.
Bohr's atomic model differed from Rutherford's because it explained that
electrons exist in specified energy levels surrounding the nucleus.
charge
having positive or negative electrical energy
All large radioactive atoms decay into smaller atoms by releasing alpha particles. Each alpha particle has 2 protons, 2 neutrons, and 0 electrons. The table below describes several neutral, low-mass atoms. An alpha particle is also referred to as a nucleus of which isotope?
helium-4
Different _____ of an element have different numbers of electrons.
ions
A cathode ray tube is made of glass with a small amount of some kind of gas in it. It has metal electrodes at each end to pick up an electric current. The electrodes are named "positive" and "negative," which were words used by Benjamin Franklin in the 1700s to describe electricity. A bright ray forms in the gas when an electric current is applied to metal electrodes. In the 1800s, an important scientist suspected that the negatively charged particles in a cathode ray were present in all atoms. What procedure would allow that scientist to investigate this idea?
making cathode ray tubes out of different materials to see if the ray is the same
An atom that has fewer neutrons than protons and more electrons than protons is a(n) ___________ ion.
negative
When an atom that has no charge loses two electrons, it becomes a
positive ion
All atoms of the same element must have the same number of
protons
Dalton's theory states that atoms are the smallest possible parts of elements. In a chemical reaction, atoms will
rearrange and form new substances with new properties.
Dalton determined that a chemical reaction was simply a(n) ______________ of atoms, not the creation of new substances.
rearrangement
atom
smallest possible particle of an element
What is an atomic nucleus?
the central part of an atom, composed of protons and neutrons
Scientists in a lab are working with two different samples of the element mercury. They know that the different samples are different isotopes. Which property of the isotopes must be different?
the mass number
The scattering of a stream of positively charged particles when striking a thin film of gold confirms that
the positive charge in an atom must be located in a dense central mass.
The first model of the atom was developed through
thinking about the smallest particles of matter without experimenting.
Based on the article "Will the real atomic model please stand up?," why did J.J. Thomson experiment with cathode ray tubes?
to determine that electric beams in cathode ray tubes were actually made of particles
Rutherford's theory was identified by
using a beam of particles and detecting the scattering of the particles after they hit gold foil.
Students are completing a table about a particular subatomic particle that helps make up an atom. What best explains how they should complete the table?
with "Inside the nucleus," because the particle is a neutron
