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Questions and Answers
How many electrons can the second energy level hold?
How many electrons can the second energy level hold?
What group do elements with full outer energy levels belong to?
What group do elements with full outer energy levels belong to?
How did Mendeleev arrange the elements in his periodic table initially?
How did Mendeleev arrange the elements in his periodic table initially?
What did Mendeleev do when he encountered elements that did not fit the patterns?
What did Mendeleev do when he encountered elements that did not fit the patterns?
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How did Mendeleev account for undiscovered elements in his periodic table?
How did Mendeleev account for undiscovered elements in his periodic table?
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What did Mendeleev do based on his confidence in his periodic table?
What did Mendeleev do based on his confidence in his periodic table?
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How is the modern periodic table arranged?
How is the modern periodic table arranged?
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Which element type is placed in Group 0 (Noble gases)?
Which element type is placed in Group 0 (Noble gases)?
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Study Notes
Atomic Structure
- An atom has protons, neutrons, and electrons.
- The number of protons defines the element, while the number of neutrons defines the isotope.
- Isotopes are atoms of an element with a different number of neutrons.
Isotopes
- Examples of isotopes: ¹⁹F (9 electrons, 10 neutrons), ⁹Be (4 electrons, 5 neutrons)
- Atoms with the same number of protons but different number of neutrons are isotopes.
Ions
- Ions are atoms that have gained or lost electrons, resulting in an overall charge.
- Positive ions have lost electrons, while negative ions have gained electrons.
Noble Gases
- Noble gases are unreactive elements with a full outer energy level.
- Examples of noble gases: He, Ne, Ar, Kr, Xe, Rn.
- Boiling points of noble gases increase as their relative atomic masses increase.
- Boiling points of noble gases: He (-289°C), Ne (-246°C), Ar (-186°C), Kr (-153°C), Xe (-108°C), Rn (-62°C).
Electron Energy Levels
- Electrons exist in energy levels (shells) with a maximum number of electrons.
- Energy level capacities: 1st level (2 electrons), 2nd level (8 electrons), 3rd level (8 electrons).
- Elements with full outer energy levels are in Group 0 (Noble gases).
Periodic Table
- Mendeleev developed the first modern periodic table, arranging elements by increasing atomic weight.
- Mendeleev predicted the properties of undiscovered elements based on their position in the table.
- The modern periodic table is arranged by atomic number, not atomic weight.
Development of the Periodic Table
- Mendeleev's table was revolutionary, as he switched element positions to fit group patterns and predicted undiscovered elements.
- The modern periodic table has undergone changes, incorporating new elements and reorganizing the table by atomic number.
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Description
Test your knowledge on the atomic structure by answering questions about the number of protons, neutrons, and electrons in various elements and isotopes.
