28 terms

7th grade science

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nucleus
In the center of an atom
Protons
Have a positive charge
Neutrons
Do not have a charge
Electrons
Have a negative charge
Low-Energy electrons
Move closer to the nucleus
High-Energy electrons
Move farther from the nucleus
Isotopes
Atoms that have the same number of protons, neutrons, but different numbers of neutrons
Mass number
Sum of the protons and neutrons in the nucleus
Periods
Go from highly reactive metals to rare gases
Groups
Also known as families, have similar characteristics
Physical properties of metals
Shininess, malleability, ductility, and conductivity
Chemical properties of metals
Reactivity which is strong, medium, or weak or non-reactive
Alkali metals
Lose one electron when reacting with other elements
Alkaline Earth Metals
Fairly hard, gray-white, and a good conductor of electricity
Transition metals
Hard and shiny, and all are good conductors of electricity
Metals in Mixed Groups
Only a few are metals and are slow to react
Lanthanides
Soft, malleable, shiny metals wit high conductivity
Actinides
Only four occur naturally and the rest are highly unstable
Synthetic metals
Elements with atomic numbers higher than 92 and are formed by using particle accelerators
Physical properties of nonmetals
Ten are gases at room temperature, solid nonmetals are dull and brittle, and they are poor conductors of heat and electricity
Chemical properties of nonmetals
Most are reactive and steadily form compounds, and their atoms usually gain or share electrons
Carbon family
Gain, lose, or share four electrons when reacting
Nitrogen family
Usually gain or share three electrons when reacting
Oxygen family
Usually gain or share two electrons when reacting
Halogen family
Typically gain or share one electron when reacting and all are very reactive and many are dangerous
Noble gases
Are usually unreactive do not gain, share, or lose electrons
Hydrogen
Simplest atom
Metalloids
Have some characteristics of both metals and nonmetals, all are solids at room temperature, and they have a varying ability to conduct electricity
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