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Atoms and their structure
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Since most of the particles went through, it was mostly empty.

Because the pieces turned so much, the positive pieces were heavy.

Small volume, big mass, big density.

This small dense positive area is the nucleus.

Slide 39

Other pieces

Other pieces

Proton - positively charged pieces 1840 times heavier than the electron.

Neutron - no charge but the same mass as a proton.

Where are the pieces?

Slide 40

Subatomic particles

Subatomic particles

Electron

Proton

Neutron

Name

Symbol

Charge

Relative

mass

Actual

mass (g)

e-

p+

n0

-1

+1

0

1/1840

1

1

9.11 x 10-28

1.67 x 10-24

1.67 x 10-24

Slide 41

Structure of the Atom

Structure of the Atom

There are two regions.

The nucleus.

With protons and neutrons.

Positive charge.

Almost all the mass.

Electron cloud- most of the volume of an atom.

The region where the electron can be found.

Slide 42

Size of an atom

Size of an atom

Atoms are small.

Measured in picometers, 10-12 meters.

Hydrogen atom, 32 pm radius.

Nucleus tiny compared to atom.

IF the atom was the size of a stadium, the nucleus would be the size of a marble.

Radius of the nucleus is near 10-15m.

Density near 1014 g/cm3.

Slide 43

Counting the Pieces

Counting the Pieces

Atomic Number = number of protons

# of protons determines kind of atom.

the same as the number of electrons in the neutral atom.

Mass Number = the number of protons + neutrons.

All the things with mass.

NOT on the periodic table

Slide 44

Isotopes

Isotopes

Dalton was wrong.

Atoms of the same element can have different numbers of neutrons.

different mass numbers.

called isotopes.

Slide 45

Symbols

Symbols

Contain the symbol of the element, the mass number and the atomic number.

Slide 46

Symbols

Symbols

Contain the symbol of the element, the mass number and the atomic number.

X

Mass

number

Atomic

number

Slide 47

Naming Isotopes

Naming Isotopes

Put the mass number after the name of the element.

carbon- 12

carbon -14

uranium-235

Slide 48

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