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Inside an Atom.

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Presentation on theme: "Inside an Atom."— Presentation transcript:

1 Inside an Atom


3 All matter is made up of one or more elements
Element: substance that cannot be broken down into smaller substances Examples: Hydrogen, Carbon, Oxygen Atom: the smallest unit of an element

4 Parts of an Atom Proton – positive charge (+)
Neutron – neutral (no charge) Electron – negative charge (-)

5 Electrons are moving rapidly in a cloud around the nucleus
Protons and neutrons are found in the nucleus in the center of the atom Electrons are moving rapidly in a cloud around the nucleus Different energy levels around the nucleus Electrons may “hang out” in these levels Valence electrons – those that are farthest from the nucleus and most loosely held


7 Properties of Atoms An atom is neutral when it has an equal number of protons (+) and electrons (-). Sometimes when one atom reacts with another atom, it gains or loses an electron giving it a positive or negative charge This charged particle is called an ION

8 Properties continued…
If an atom loses an electron (-), it now has a positive charge (cation) If an atom gains an electron (-), it now has a negative charge (anion)

9 More Properties Atomic Number – number of protons
Identifies and determines the element Carbon: atomic # 6 Sodium: atomic # 11 Gold: atomic # 79 Atomic mass – average mass of one atom of an element

10 Atomic Mass Unit (amu) SI unit used to measure the mass of particles in atoms Protons and Neutrons = 1 amu Approximately 2000 Electrons = 1 amu Almost all of an atom’s mass is in the nucleus

11 Isotopes The number of protons for a certain atom never changes, but sometimes an atom may have different numbers of neutrons Mass Number – sum of protons and neutrons

12 Hydrogen Isotopes

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