Period vs. Group — What's the Difference?
Edited by Tayyaba Rehman — By Fiza Rafique — Updated on May 15, 2024
Period refers to horizontal rows on the periodic table, indicating increasing principal quantum numbers, while a group denotes vertical columns, representing elements with similar valence electron configurations.
Difference Between Period and Group
Table of Contents
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Key Differences
In the periodic table, a period consists of elements arranged in horizontal rows. These elements have electrons filling up the same principal energy level, which increases as one moves from one period to the next. On the other hand, a group contains elements placed in vertical columns, characterized by having the same number of electrons in their outer shell, which influences their chemical properties and reactivity.
Elements in a period show a gradual change in properties from metallic to non-metallic as you move from left to right. This transition is due to the increasing nuclear charge that attracts electrons more strongly, affecting their chemical behavior. Whereas, elements within the same group exhibit similar chemical properties because they have the same number of valence electrons, which are primarily responsible for chemical bonding and reactions.
The length of each period varies: the first period has only two elements, while later periods have up to 32 elements. This variation is due to the filling of different orbital types (s, p, d, f) as the atomic number increases. In contrast, each group typically contains elements that share a common pattern in their electron configuration, particularly in the outermost shells, leading to similarities in how they interact chemically.
The reactivity of elements within a period generally decreases from left to right, primarily due to the increasing electronegativity and ionization energy. Conversely, the reactivity of elements in a group often increases from top to bottom, as atomic size increases, making the outer electrons more easily accessible for bonding.
In terms of ionization energy, elements in a period tend to have higher ionization energies as you move towards the right, due to closer and tighter binding of the electrons by the nucleus. However, within a group, ionization energy decreases down the group as the electrons are further from the nucleus, making them easier to remove.
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Comparison Chart
Arrangement
Horizontal rows
Vertical columns
Element Properties
Changes from metallic to non-metallic across the period
Consistent within the group due to similar valence electron configurations
Reactivity Change
Decreases from left to right
Generally increases from top to bottom
Example of Change
Na (metallic) to Ne (non-metallic)
Li, Na, K (all alkali metals)
Chemical Behavior
Varies significantly across a period
Remains similar within a group
Compare with Definitions
Period
Represents a gradual increase in atomic number in a single row.
Moving across a period, each element has one more proton than the last.
Group
A vertical column in the periodic table.
The halogens form a group, known for their reactivity.
Period
An interval of time characterized by the occurrence of a certain condition, event, or phenomenon
A period of economic prosperity.
Group
Elements with the same number of valence electrons.
All elements in Group 1 have one valence electron.
Period
An interval of time characterized by the prevalence of a specified culture, ideology, or technology
Artifacts of the pre-Columbian period.
Group
Typically exhibits similar chemical and physical properties.
Group 17 elements are all nonmetals with high electronegativities.
Period
An interval regarded as a distinct evolutionary or developmental phase
Picasso's early career is divided into his blue period and rose period.
Group
Reactivity tends to increase from top to bottom within the group.
Francium is more reactive than cesium in the same group.
Period
(Geology) A unit of time, longer than an epoch and shorter than an era.
Group
Characterized by a consistent pattern in electron configuration.
The outer electron structure for Group 2 elements is always s2.
Period
Any of the divisions of the academic day.
Group
An assemblage of persons or objects gathered or located together; an aggregation
A group of dinner guests.
A group of buildings near the road.
Period
Sports & Games A division of the playing time of a game.
Group
A set of two or more figures that make up a unit or design, as in sculpture.
Period
Physics & Astronomy The time interval between two successive occurrences of a recurrent event or phases of an event; a cycle
The period of a satellite's orbit.
Group
A number of individuals or things considered or classed together because of similarities
A small group of supporters across the country.
Period
A point or portion of time at which something is ended; a completion or conclusion.
Group
(Linguistics) A category of related languages that is less inclusive than a family.
Period
A punctuation mark ( . ) indicating a full stop, placed at the end of declarative sentences and other statements thought to be complete, and after many abbreviations.
Group
A military unit consisting of two or more battalions and a headquarters.
Period
The full pause at the end of a spoken sentence.
Group
A unit of two or more squadrons in the US Air Force, smaller than a wing.
Period
A sentence of several carefully balanced clauses in formal writing.
Group
Two or more atoms behaving or regarded as behaving as a single chemical unit.
Period
A metrical unit of quantitative verse consisting of two or more cola.
Group
A column in the periodic table of the elements.
Period
An analogous unit or division of classical Greek or Latin prose.
Group
(Geology) A stratigraphic unit, especially a unit consisting of two or more formations deposited during a single geologic era.
Period
(Music) A group of two or more phrases within a composition, often made up of 8 or 16 measures and terminating with a cadence.
Group
(Mathematics) A set, together with a binary associative operation, such that the set is closed under the operation, the set contains an identity element for the operation, and each element of the set has an inverse element with respect to the operation. The integers form a group under the operation of ordinary addition.
Period
The least interval in the range of the independent variable of a periodic function of a real variable in which all possible values of the dependent variable are assumed.
Group
Of, relating to, constituting, or being a member of a group
A group discussion.
A group effort.
Period
A group of digits separated by commas in a written number.
Group
To place or arrange in a group
Grouped the children according to height.
Period
The number of digits that repeat in a repeating decimal. For example, 1/7 = 0.142857142857 ... has a six-digit period.
Group
To belong to or form a group
The soldiers began to group on the hillside.
Period
(Chemistry) A sequence of elements arranged in order of increasing atomic number and forming one of the horizontal rows in the periodic table.
Group
A number of things or persons being in some relation to one another.
There is a group of houses behind the hill;
He left town to join a Communist group
A group of people gathered in front of the Parliament to demonstrate against the Prime Minister's proposals.
Period
Of, belonging to, or representing a certain historical age or time
A period piece.
Period furniture.
Group
(group theory) A set with an associative binary operation, under which there exists an identity element, and such that each element has an inverse.
Period
Used to emphasize finality, as when expressing a decision or an opinion
You're not going to the movies tonight, period!.
Group
An effective divisor on a curve.
Period
A length of time.
There was a period of confusion following the announcement.
You'll be on probation for a six-month period.
Group
A (usually small) group of people who perform music together.
Did you see the new jazz group?
Period
A period of time in history seen as a single coherent entity; an epoch, era.
Food rationing continued in the post-war period.
Group
(astronomy) A small number (up to about fifty) of galaxies that are near each other.
Period
The punctuation mark “.” (indicating the ending of a sentence or marking an abbreviation).
Group
(chemistry) A column in the periodic table of chemical elements.
Period
(figurative) A decisive end to something; a stop.
Group
(chemistry) A functional group.
Nitro is an electron-withdrawing group.
Period
The length of time during which the same characteristics of a periodic phenomenon recur, such as the repetition of a wave or the rotation of a planet.
Group
(sociology) A subset of a culture or of a society.
Period
A section of an artist's, writer's (etc.) career distinguished by a given quality, preoccupation etc.
This is one of the last paintings Picasso created during his Blue Period.
Group
(military) An air force formation.
Period
Each of the divisions into which a school day is split, allocated to a given subject or activity.
I have math class in second period.
Group
(geology) A collection of formations or rock strata.
Period
Each of the intervals, typically three, of which a game is divided.
Gretzky scored in the last minute of the second period.
Group
(computing) A number of users with the same rights with respect to accession, modification, and execution of files, computers and peripherals.
Period
One or more additional intervals to decide a tied game, an overtime period.
They won in the first overtime period.
Group
An element of an espresso machine from which hot water pours into the portafilter.
Period
The length of time for a disease to run its course.
Group
(music) A number of eighth, sixteenth, etc., notes joined at the stems; sometimes rather indefinitely applied to any ornament made up of a few short notes.
Period
An end or conclusion; the final point of a process etc.
Group
(sports) A set of teams playing each other in the same division, while not during the same period playing any teams that belong to other sets in the division.
Period
(rhetoric) A complete sentence, especially one expressing a single thought or making a balanced, rhythmic whole.
Group
(business) A commercial organization.
Period
(obsolete) A specific moment during a given process; a point, a stage.
Group
(transitive) To put together to form a group.
Group the dogs by hair colour
Period
(chemistry) A row in the periodic table of the elements.
Group
(intransitive) To come together to form a group.
Period
(geology) A geochronologic unit of millions to tens of millions of years; a subdivision of an era, and subdivided into epochs.
These fossils are from the Jurassic period.
Group
A cluster, crowd, or throng; an assemblage, either of persons or things, collected without any regular form or arrangement; as, a group of men or of trees; a group of isles.
Period
(genetics) A Drosophila gene, the gene product of which is involved in regulation of the circadian rhythm.
Group
An assemblage of objects in a certain order or relation, or having some resemblance or common characteristic; as, groups of strata.
Period
(music) Two phrases (an antecedent and a consequent phrase).
Group
A variously limited assemblage of animals or plants, having some resemblance, or common characteristics in form or structure. The term has different uses, and may be made to include certain species of a genus, or a whole genus, or certain genera, or even several orders.
Period
(math) The length of an interval over which a periodic function, periodic sequence or repeating decimal repeats; often the least such length.
Group
A number of eighth, sixteenth, etc., notes joined at the stems; - sometimes rather indefinitely applied to any ornament made up of a few short notes.
Period
(archaic) End point, conclusion.
Group
To form a group of; to arrange or combine in a group or in groups, often with reference to mutual relation and the best effect; to form an assemblage of.
The difficulty lies in drawing and disposing, or, as the painters term it, in grouping such a multitude of different objects.
Period
Designating anything from a given historical era. en
A period car
A period TV commercial
Group
Any number of entities (members) considered as a unit
Period
Evoking, or appropriate for, a particular historical period, especially through the use of elaborate costumes and scenery.
Group
(chemistry) two or more atoms bound together as a single unit and forming part of a molecule
Period
That's final; that's the end of the matter (analogous to a period ending a sentence); end of story.
I know you don't want to go to the dentist, but your teeth need to be checked, period!
Group
A set that is closed, associative, has an identity element and every element has an inverse
Period
To come to a period; to conclude.
Group
Arrange into a group or groups;
Can you group these shapes together?
Period
To put an end to.
Group
Form a group or group together
Period
A portion of time as limited and determined by some recurring phenomenon, as by the completion of a revolution of one of the heavenly bodies; a division of time, as a series of years, months, or days, in which something is completed, and ready to recommence and go on in the same order; as, the period of the sun, or the earth, or a comet.
Period
A stated and recurring interval of time; more generally, an interval of time specified or left indefinite; a certain series of years, months, days, or the like; a time; a cycle; an age; an epoch; as, the period of the Roman republic.
How by art to make plants more lasting than their ordinary period.
Period
One of the great divisions of geological time; as, the Tertiary period; the Glacial period. See the Chart of Geology.
Period
The termination or completion of a revolution, cycle, series of events, single event, or act; hence, a limit; a bound; an end; a conclusion.
So spake the archangel Michael; then paused,As at the world's great period.
Evils which shall never end till eternity hath a period.
This is the period of my ambition.
Period
A complete sentence, from one full stop to another; esp., a well-proportioned, harmonious sentence.
Periods are beautiful when they are not too long.
Period
The punctuation point [.] that marks the end of a complete sentence, or of an abbreviated word.
Period
One of several similar sets of figures or terms usually marked by points or commas placed at regular intervals, as in numeration, in the extraction of roots, and in circulating decimals.
Period
The time of the exacerbation and remission of a disease, or of the paroxysm and intermission.
Period
A complete musical sentence.
Period
To put an end to.
Period
To come to a period; to conclude. [Obs.] "You may period upon this, that," etc.
Period
An amount of time;
A time period of 30 years
Hastened the period of time of his recovery
Picasso's blue period
Period
One of three periods of play in hockey games
Period
A stage in the history of a culture having a definable place in space and time;
A novel from the Victorian period
Period
The interval taken to complete one cycle of a regularly repeating phenomenon
Period
A punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations;
In England they call a period a stop
Period
A unit of geological time during which a system of rocks formed;
Ganoid fishes swarmed during the earlier geological periods
Period
The end or completion of something;
Death put a period to his endeavors
A change soon put a period to my tranquility
Period
A horizontal row in the periodic table.
The elements helium and neon are in the same period.
Period
A sequence of elements with electrons filling a particular principal energy level.
The third period starts with sodium and ends with argon.
Period
Shows a trend of increasing ionization energy and electronegativity.
In any period, ionization energy increases as you move from left to right.
Period
Indicates varying properties from metallic to non-metallic within the same row.
Silicon, a metalloid, lies between the metallic aluminum and the non-metallic phosphorus in a period.
Common Curiosities
What defines a period on the periodic table?
A period is defined by elements that are arranged in a horizontal row and share the same principal energy level.
How are groups identified in the periodic table?
Groups are identified by their vertical arrangement and elements within a group have the same number of electrons in their outermost shell.
How does atomic size change within a period?
Atomic size decreases from left to right within a period due to increasing nuclear attraction affecting the electron cloud.
What causes the properties of elements to change across a period?
The increase in nuclear charge across a period affects electron attraction and chemical properties.
Why do elements in the same group have similar chemical properties?
Because they have similar valence electron configurations, which determine their chemical behavior.
What role does electronegativity play in determining the properties of elements in a period?
Electronegativity, indicating an atom's ability to attract electrons, increases across a period, influencing chemical bonds and reactivity.
How does the reactivity of metals differ from the left side to the right side of a period?
Metal reactivity decreases from left to right across a period due to increased nuclear charge and electron affinity.
What trend in ionization energy can be observed within a group?
Ionization energy decreases down a group as atomic size increases and the outer electrons become more shielded.
Can elements move between periods and groups?
No, each element’s position based on its atomic structure is fixed in the periodic table.
How do the properties of nonmetals differ within a period?
Nonmetals tend to have higher ionization energies and electronegativities, making them less reactive than metals within the same period.
Why are alkali metals so reactive?
Alkali metals are highly reactive due to their single valence electron, which is easily lost in chemical reactions.
Are there any exceptions to the typical properties of groups?
Yes, transition metals and noble gases often exhibit unique behaviors not completely aligned with their group trends.
What is the significance of the electron configuration in understanding group behavior?
Electron configuration helps predict how elements are likely to react chemically, influencing their placement in groups.
What is a simple way to remember the difference between periods and groups?
Remember: Periods are horizontal and increase principal quantum levels; groups are vertical and enhance similar behaviors due to shared valence electrons.
How does the filling of electron orbitals affect the length of a period?
The filling of s, p, d, and f orbitals dictates the number of elements in each period, with more complex orbitals accommodating more elements.
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Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
