By what two criteria does the periodic table arrange chemical elements?
By atomic number and recurring chemical and physical properties.
What do periodic table periods represent in terms of electron shells?
The number of electron shells.
How are groups or families arranged in the periodic table?
They are vertical columns whose elements share similar properties due to their external electron configuration.
What pattern in element properties did Mendeleïev observe?
Sequences in their properties.
Which scientist established the idea of periodicity by observing sequences in element properties?
Mendeleïev.
In which year did Moseley discover the atomic number ?
1913.
Which criterion did Moseley establish as most important for periodic classification?
Atomic number .
How are elements ordered in modern periodic classification?
By increasing atomic number.
How many periods does the periodic table have?
Seven periods.
How many elements are in the second period?
Eight elements.
What are the atomic-number endpoints of the third period?
Sodium (Z = 11) and argon (Z = 18).
Which subshells fill progressively in the third period?
The 3s and 3p subshells.
How many elements are in the fourth period, and how many energy levels do their electrons occupy?
18 elements; four energy levels.
How many elements are in the fifth period?
18 elements.
How many elements does the sixth period contain?
32 elements.
Which energy level begins to be occupied in the sixth period?
The sixth energy level.
How many elements are in the sixth-period lanthanide series?
14 elements.
What is the status of the seventh period?
It is incomplete.
How many outermost-shell electrons do elements in the same column have?
The same number.
What are valence electrons?
Electrons in the outermost shell that determine an atom’s or element’s chemical properties, including its ability to bond.
What four blocks divide the periodic table?
The s, p, d, and f blocks.
What does periodic table organization help explain about electronegativity, atomic radius, and ionization energy?
Their trends.
What does periodic table organization help predict about elements?
Element behavior.
Which subshell fills during the first period?
The 1s subshell.
Which elements are in the first period?
Hydrogen and helium.
Which subshells contain neon’s six 2p electrons?
The 2p subshell.
How many electrons does neon have in its 2s subshell?
Two electrons.
Which subshell fills progressively from scandium to zinc in the fourth period?
The 3d subshell.
What is chromium’s electron configuration, rather than its expected configuration?
What is copper’s electron configuration, rather than its expected configuration?
Which elements mark the beginning and end of the fifth-period transition series?
Yttrium and cadmium.
Which subshell fills progressively across the fifth-period transition series?
The 4d subshell.
What happens to palladium’s 5s² subshell as its 4d orbitals become filled?
The 5s² subshell empties.
How many ordinary transition elements does the sixth period include?
10 elements.
How many seventh-period elements occur naturally?
Only the first six occur naturally.
What defines a periodic-table family or group?
Elements with the same number of electrons in the peripheral shell.
How are periodic-table groups designated by Roman numerals?
Their numerals correspond to their numbers of valence electrons.
How are groups subdivided?
Into subgroups A and B.
Why does the periodic table have 16 families across 18 columns?
Group VIII B occupies three columns.
What kinds of elements does subgroup A comprise?
Metals, nonmetals, and noble gases.
How are subgroup A’s eight families arranged?
According to progressive filling of the peripheral shell.
How many elements form the actinide series?
Fourteen elements.
Which chemist proposed an early form of the periodic table?
Dimitri Mendeleïev.
How did Mendeleïev arrange the 63 elements known in his time?
In increasing order of atomic mass.
Which elements, together with the lanthanides, constitute the rare earths?
Scandium and yttrium.
Answer 7 questions on Periodic Table and Periodicity.
1. A student uses the periodic table to classify an element and predict its behavior. Which statements describe features that support this task?
2. Which statements correctly identify Moseley's contribution to periodic classification?
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