atomic concepts.....aim 1

how did the atomic model evolved over time?

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aim 2.....

 

HW From textbook “CHEMISTRY a Contemporary Approach”

The hard sphere model

Atoms are hard, indivisible spheres of different sizes and they combined in simple whole-number ratios to form compounds.

 

The plum-pudding model

Negatively charged particles (electrons) are part of the internal structure of atoms.

 

The planetary model

Experiments including the "gold foil experiment," led to the conclusion that a small, dense positively charge nucleus is at the center of the atom with shells of electrons moving about in the empty space surrounding the nucleus.

 

 

 

The wave-mechanical model (electron cloud model)

Electrons are in fact not moving like the planets around the sun but are located in regions (orbitals) in the empty space. The wave-mechanical model of the atom is required to explain the spectra of elements with multi electron atoms

 

The modern model of the atom has evolved over a long period of time through the work of many scientists.

    

TEST YOUR UNDERSTANDING

1/07

4 Which group of atomic models is listed in historical order from the earliest to the most recent?

        (1) hard-sphere model, wave-mechanical model, electron-shell model

        (2) hard-sphere model, electron-shell model, wave-mechanical model

        (3) electron-shell model, wave-mechanical model, hard-sphere model

        (4) electron-shell model, hard-sphere model, wave-mechanical model

6/07

1 According to the wave-mechanical model of the atom, electrons in an atom

        (1) travel in defined circles           (2) are most likely found in an excited state

        (3) have a positive charge            (4) are located in orbitals outside the nucleus

8/07

1 What was concluded about the structure of the atom as the result of the gold foil experiment?

        (1) A positively charged nucleus is surrounded by positively charged particles.

        (2) A positively charged nucleus is surrounded by mostly empty space.

        (3) A negatively charged nucleus is surrounded by positively charged particles.

        (4) A negatively charged nucleus is surrounded by mostly empty space.

1/06

4 Which sequence represents a correct order of historical developments leading to the modern model of the atom?

    (1) the atom is a hard sphere → most of the atom is empty space → electrons exist in orbitals outside the nucleus

    (2) the atom is a hard sphere → electrons exist in orbitals outside the nucleus → most of the atom is empty space

    (3) most of the atom is empty space →electrons exist in orbitals outside the nucleus → the atom is a hard sphere

    (4) most of the atom is empty space →the atom is a hard sphere → electrons exist in orbitals outside the nucleus

8/06

1 Which statement correctly describes the charge of the nucleus and the charge of the electron cloud of an atom?

    (1) The nucleus is positive and the electron cloud is positive.

    (2) The nucleus is positive and the electron cloud is negative.

    (3) The nucleus is negative and the electron cloud is positive.

    (4) The nucleus is negative and the electron cloud is negative.

1/05

3 Which conclusion is based on the “gold foil experiment” and the resulting model of the atom?

                (1) An atom is mainly empty space, and the nucleus has a positive charge.

                (2) An atom is mainly empty space, and the nucleus has a negative charge.

                (3) An atom has hardly any empty space, and the nucleus has a positive charge.

                (4) An atom has hardly any empty space, and the nucleus has a negative charge.

6/05

65 In the early 1900s, experiments were conducted to determine the structure of the atom. One of these experiments involved bombarding gold foil with alpha particles. Most alpha particles passed directly through the foil. Some, however, were deflected at various angles. Based on this alpha particle experiment, state two conclusions that were made concerning the structure of an atom.

6/04

1 The modern model of the atom is based on the work of
        (1) one scientist over a short period of time (2) one scientist over a long period of time
        (3) many scientists over a short period of time (4) many scientists over a long period of time

1/03

Base your answers on the information and diagram below.

One model of the atom states that atoms are tiny particles composed of a uniform mixture of positive and negative charges. Scientists conducted an experiment where alpha particles were aimed at a thin layer of gold atoms. Most of the alpha particles passed directly through the gold atoms. A few alpha particles were deflected from their straight-line paths. An illustration of the experiment is shown below.

        1.  Most of the alpha particles passed directly through the gold atoms undisturbed. What does this evidence suggest about the structure of the gold atoms? 

        2. A few of the alpha particles were deflected. What does this evidence suggest about the structure of the gold atoms?

        3. How should the original model be revised based on the results of this experiment? 

6/03 John Dalton was an English scientist who proposed that atoms were hard, indivisible spheres. In the modern model, the atom has a different internal structure.

        a) Identify one experiment that led scientists to develop the modern model of the atom.

        b) Describe this experiment.

        c) State one conclusion about the internal structure of the atom, based on this experiment.

8/02

 Subatomic particles can usually pass undetected through an atom because the volume of an atom is composed of

            (1) an uncharged nucleus           (2) largely empty space             (3) neutrons                  (4) protons

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