What is the periodic table?
The periodic table is an ordered arrangement of chemical elements into rows (periods) and columns (groups) based on increasing atomic number, showing periodic recurrence of properties.
What does the periodic law state?
The periodic law states that when elements are arranged in order of their atomic numbers, an approximate recurrence of their properties is evident.
Who created the first widely accepted periodic table?
Dmitri Mendeleev, a Russian chemist, created the first widely accepted periodic table in 1869.
How did Mendeleev use the periodic law?
Mendeleev used the periodic law to predict properties of missing elements, leaving gaps in his table for undiscovered elements.
What is a group in the periodic table?
A group is a vertical column in the periodic table; elements in the same group have similar chemical properties and the same number of electrons in their outermost subshell.
What is a period in the periodic table?
A period is a horizontal row in the periodic table; a new period starts when a new electron shell begins to fill.
How does metallic character change across a period?
Metallic character decreases from left to right across a period.
How does metallic character change down a group?
Metallic character increases down a group.
How does nonmetallic character trend on the periodic table?
Nonmetallic character increases from bottom left to top right of the periodic table.
What is atomic number (Z)?
Atomic number (Z) is the number of protons in the nucleus of an atom; it uniquely identifies a chemical element.
What are isotopes?
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
How are isotopes represented in the periodic table?
Isotopes are not separated; they are grouped together under a single element. The atomic mass shown is usually the weighted average of naturally occurring isotopes.
What is a chemical symbol?
A chemical symbol is a one- or two-letter abbreviation for an element, e.g., H for hydrogen, He for helium.
What are the four blocks of the periodic table?
The periodic table is divided into four blocks: s-block, p-block, d-block, and f-block, based on the subshell being filled.
Why do elements in the same group have similar chemical properties?
Elements in the same group have the same number of electrons in their outermost subshell, leading to similar chemical behavior.
What did Glenn T. Seaborg discover about the periodic table?
Glenn T. Seaborg discovered that the actinides are f-block elements, not d-block, leading to the modern form of the table in 1945.
What is the atomic number of hydrogen?
Hydrogen has atomic number 1.
What is the atomic number of helium?
Helium has atomic number 2.
What is the atomic number of lithium?
Lithium has atomic number 3.
How many naturally occurring elements exist?
In nature, only elements up to atomic number 94 exist; elements beyond that are synthesized in laboratories.
What determines the order of elements in the periodic table?
Elements are listed in order of increasing atomic number.
What is the trend in nonmetallic character from left to right across a period?
Nonmetallic character increases from left to right across a period.
What is the trend in metallic character from top to bottom in a group?
Metallic character increases from top to bottom in a group.