Chemistry and M.E.A.PThe benchmarks and you!

PME. Matter and Energy Benchmark 3

Explain how elements differ, in terms of the structural parts

and electrical charges of atoms.

Key concepts:

Parts of atoms—nucleus, electron cloud.

Subatomic particles—proton, neutron, electron.

Electrical charges—positive, neutral, negative.

Each element has a unique number of protons = atomic number!

Electrons and protons havean attribute called charge.

Electrons have a negativecharge. e = 1.6 x 10-19 Coulomb

Protons are 1800 times moremassive, and have a positivecharge.

(Neutrons have no charge.)

sol.sci.uop.edu/.../chapter8/ chapter8.html

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Real World Context:

Elements

Interactive Tutorialhttp://wwww.hamline.edu/~olerun/ole.cgi/C1/P1/S1

Interactive Periodic Tablehttp://www.chemistry.org/portal/a/c/s/1/acsdisplay.html?DOC=sitetools\periodic_table.html#

In the past, atoms were envisioned to be positively charged spheres embeddedwith negatively charged electrons like raisins in a cake. This is incorrectbecause atoms were shown to

A have nuclei at their centers.B have only negative particles.C contain very little empty space.

D consist of particles that are equal in mass.

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B have only negative particles.

This is inaccurate because atoms were shown to havesubatomic particles:

Positively charged protons

No charge neutrons

Negatively charged electrons

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C contain very little empty space.

This is incorrect because atoms were shown to be mostly empty space.

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D consist of particles that are equal in mass.

This inaccurate because electrons have less mass thanprotons and neutrons.

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How does the structure of elements vary?

a) All elements have the same number of protons

b) All elements have the same number of electrons

c) Each element has a specific number of protons

d) Each element has a specific number of neutrons

e) Each element has a specific electrical charge

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a.Each element has a specific number of protons: Hydrogen has one, helium has two, carbon has six

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b. An element usually has the same number of electrons and protons. Oxygen has 8 protons and 8 electrons. So different elements have different numbers of electrons

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d. Elements can have different numbers of neutrons. When they have a different number than usual it is called an isotope

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e. Quite often elements are neutral, but can become electrically charged. These are called ions.

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