Modern atom
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Modern Atom. Basic Structure. Consists of tiny nucleus and the electrons that move about it Nucleus diameter about 10 -13 cm Electron is average distance of 10 -8 cm from the nucleus. Nucleus. Chemistry is mostly about the electrons

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Presentation Transcript

Basic structure
Basic Structure

  • Consists of tiny nucleus and the electrons that move about it

  • Nucleus diameter about 10-13 cm

  • Electron is average distance of 10-8 cm from the nucleus


Nucleus
Nucleus

  • Chemistry is mostly about the electrons

  • Nucleus has a very high density (a lot of mass and small area)


Nuclear contents
Nuclear Contents

  • Protons – positively charged with charge about equal to but opposite of the electrons

  • Neutrons – no charge and about same mass as protons


What causes different properties
What Causes Different Properties

  • Electrons are the parts that intermingle with other atoms

  • Different number of electrons (thus protons) causes different interactions and thus different behavior


Atoms are very small in mass
Atoms Are Very Small In Mass

  • Hard to express in grams

  • Unit of atomic mass – amu

    • 1 amu = 1.66 x 10-24 g


Masses of subatomic particles
Masses of Subatomic Particles

  • Proton 1.0073 amu

  • Neutron 1.0087 amu

  • Electron 5.486 x 10-4 amu

  • It takes 1836 electrons to equal the mass of 1 proton


In general
In General

  • In a neutral atom the number of protons is equal to the number of electrons

  • The number of protons determines the identity of the atom

  • All atoms of the same element have the same number of protons


  • Isotopes – are atoms of the same element with different numbers of neutrons (thus different masses)

  • Isotopes are also called Nuclides

  • Atomic mass on the periodic table is the weighted average of the masses of all naturally occurring isotopes

  • Ions – atoms with different numbers of protons and electrons


Notation
Notation

  • Mass number shows the total number of protons and neutrons

  • Atomic number shows the number of protons


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