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The periodic table key terms
Study The periodic table with curriculum-aligned Key Terms resources, practice links, and exam-focused support.
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key terms
Resource type
Topic
The periodic table
Key terms
atomic number
The number of protons in the nucleus of an atom, which determines the element's position in the periodic table.
periodic table
A tabular arrangement of elements organized by increasing atomic number, showing periodic trends in properties.
group
A column in the periodic table where elements share similar properties and have the same number of outer-shell electrons.
periodic table
A systematic arrangement of elements in order of atomic number, showing the relationships between them.
group
A column in the periodic table where elements have the same number of outer-shell electrons.
outer-shell electrons
Electrons located in the outermost shell of an atom that determine its chemical properties.
outer-shell electrons
Electrons located in the highest energy level of an atom that determine its chemical properties.
similar chemical properties
Chemical behaviors that are alike among elements in the same group due to their identical number of outer-shell electrons.
atomic number
The number of protons in the nucleus of an atom, which determines the element's position in the periodic table.
electron arrangement
The distribution of electrons in an atom's electron shells, which influences the element's chemical properties and position in the periodic table.
reactivity
the tendency of an element to undergo a chemical reaction, influenced by its position in the periodic table.
periodic table
a tabular arrangement of elements ordered by atomic number, showing periodic trends in properties.
atomic weight
The mass of an element's atoms, used by early scientists to arrange elements in the periodic table.
Mendeleev
A scientist who developed an early version of the periodic table and left gaps for undiscovered elements.
incomplete periodic tables
Early periodic tables lacked some elements and did not account for all properties.
arrangement by atomic weight
The method used by early scientists to organize elements before the discovery of subatomic particles.
inappropriate groups
Groups in the periodic table where elements do not share similar properties due to strict adherence to atomic weight order.
atomic weight order
The arrangement of elements based on their atomic weight, which led to misclassification in early periodic tables.
Mendeleev
A scientist who developed an early version of the periodic table and left gaps for undiscovered elements.
gaps
Spaces in the periodic table indicating the presence of undiscovered elements, as predicted by Mendeleev.
Mendeleev
A chemist who developed the periodic table and rearranged elements based on their chemical properties.
chemical properties
Characteristics of a substance that determine how it reacts with other substances.
Mendeleev
A chemist who developed the periodic table and rearranged elements based on their chemical properties.
predicted elements
Elements that were forecasted by Mendeleev based on gaps in his periodic table, which were later discovered.
isotope
Atoms of the same element with the same number of protons but different numbers of neutrons.
atomic weight order
The arrangement of elements based on their average atomic mass, which can be affected by the presence of isotopes.
testing predictions
The process of conducting experiments or observations to verify the accuracy of scientific hypotheses.
support or refute
To provide evidence that either confirms (supports) or disproves (refutes) a scientific idea.
metal
An element that reacts to form positive ions.
positive ion
A charged particle formed when an atom loses one or more electrons.
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