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Period vs. Group: Know the Difference

Shumaila Saeed
By Shumaila Saeed || Published on February 16, 2024
In the periodic table, a period refers to a horizontal row, indicating elements with the same number of atomic orbitals, while a group is a vertical column representing elements with similar chemical properties due to the same number of valence electrons.
Period vs. Group

Key Differences

A period in the periodic table refers to the horizontal rows. Each period indicates a new atomic shell being filled with electrons. In contrast, a group, also known as a family, consists of elements in a vertical column. Groups are significant in the periodic table because elements within the same group share similar chemical properties due to having the same number of valence electrons.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024
The number of periods in the periodic table indicates the number of electron shells an atom can have. For example, elements in the second period have electrons in two shells. Meanwhile, elements in a group share similar chemical reactivity and valence electron configuration, like the elements in Group 1, which are all alkali metals and have one electron in their outermost shell.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024
As we move across a period from left to right, the atomic number increases, and elements change from metals to metalloids and nonmetals. However, within a group, despite an increase in atomic number as we move down, the elements maintain similar characteristics, such as the halogens in Group 17, which are all nonmetals and highly reactive.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024
The length of each period varies: the first period has only two elements, while later periods have more, reflecting the increasing number of electrons that can be accommodated in higher energy levels. In groups, the number of elements varies depending on the group's position in the periodic table, but the elements within a group always have similar patterns of electron shells.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024
Periods are crucial for understanding the electron configuration and predicting the atomic radius of elements, as atomic radius generally decreases across a period. Groups, on the other hand, help in predicting the reactivity and valency of elements, as these properties are consistent within a group.
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Shumaila Saeed
Feb 16, 2024
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Comparison Chart

Orientation

Horizontal rows in the periodic table.
Vertical columns in the periodic table.
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Feb 16, 2024

Represents

Elements with the same number of atomic orbitals.
Elements with similar properties due to same number of valence electrons.
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Atomic Number

Increases across a period.
Increases down a group.
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Feb 16, 2024

Electron Configuration

Change across a period, adding electrons to the same shell.
Similar in a group, differing in the number of shells.
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Chemical Properties

Vary across a period (from metallic to nonmetallic).
Generally similar within a group.
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Feb 16, 2024
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Example

Oxygen and Fluorine are in the same period but have different properties.
Chlorine and Bromine are in the same group and share similar properties.
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Period and Group Definitions

Period

A period is a specific duration of time.
The project will be completed over a period of six months.
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Jan 18, 2024

Group

In music, a group refers to a band or ensemble.
The Beatles were a popular music group in the 1960s.
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Jan 18, 2024

Period

In science, a period is the time for a complete cycle of a wave.
The period of the pendulum's swing depends on its length.
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Shumaila Saeed
Jan 18, 2024

Group

A group is a collection of individuals or items.
The study group meets every Wednesday evening.
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Shumaila Saeed
Jan 18, 2024
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Period

In menstruation, a period is the monthly bleeding in women.
Her period is usually regular every month.
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Jan 18, 2024

Group

In chemistry, a group is a column of elements in the periodic table with similar properties.
The halogens are found in the same group in the periodic table.
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Shumaila Saeed
Jan 18, 2024

Period

(chemistry) A row in the periodic table of the elements.
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Shumaila Saeed
Jan 15, 2024

Group

In organizational contexts, a group is a unit or department within a larger entity.
She works in the marketing group of the company.
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Jan 18, 2024

Period

In grammar, a period is a punctuation mark indicating the end of a sentence.
Make sure to put a period at the end of each sentence.
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Shumaila Saeed
Jan 18, 2024

Group

A column in the periodic table of the elements.
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Period

Period refers to a historical era with distinctive characteristics.
The Victorian period was known for its unique architectural style.
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Jan 18, 2024

Group

(chemistry) A column in the periodic table of chemical elements.
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Group

(chemistry) A functional group.
Nitro is an electron-withdrawing group.
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Group

In mathematics, a group is a set equipped with an operation that combines any two of its elements to form a third element.
The set of integers forms a group under addition.
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Jan 18, 2024

Repeatedly Asked Queries

What does a period signify in the periodic table?

In the periodic table, a period signifies a horizontal row of elements.
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Shumaila Saeed
Feb 16, 2024

How does atomic size change across a period?

Atomic size generally decreases as you move across a period.
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Shumaila Saeed
Feb 16, 2024

What does a group signify in the periodic table?

In the periodic table, a group signifies a vertical column of elements.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

How does reactivity change within a group?

Reactivity in a group varies, often increasing down the group in metals and decreasing in nonmetals.
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Shumaila Saeed
Feb 16, 2024

Can elements in the same period have different properties?

Yes, elements in the same period can have varied properties.
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Shumaila Saeed
Feb 16, 2024

Why are elements in the same group chemically similar?

Elements in the same group have similar electron configurations, leading to similar chemical properties.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Can a period refer to a historical time frame?

Yes, a period can refer to a specific historical era.
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Shumaila Saeed
Feb 16, 2024

Does a period in science have a different meaning than in history?

Yes, in science, a period often refers to the time of a cycle, different from its historical meaning.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

What is a period in grammar?

In grammar, a period is a punctuation mark used to end a sentence.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Is the term 'group' used in mathematics?

Yes, in mathematics, a group is a set with an operation that combines elements in a specific way.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

How many periods are there in the periodic table?

There are seven periods in the standard periodic table.
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Shumaila Saeed
Feb 16, 2024

What is the significance of group numbers in the periodic table?

Group numbers indicate the number of valence electrons in the elements.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Is the term 'period' used in music?

In music, period can refer to a specific duration of a musical piece.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

How are periods and groups arranged in the modern periodic table?

Periods are arranged horizontally, and groups are arranged vertically in the periodic table.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

What's the difference between groups and periods in terms of electron shells?

In periods, electrons fill the same shell, while in groups, electrons fill different shells.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Are there exceptions to trends in periods and groups in the periodic table?

Yes, there are exceptions due to factors like electron shielding and atomic size.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Are all elements in a group found in the same state of matter?

No, elements in a group can exist in different states of matter.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

What is an example of a group in chemistry?

An example is the alkali metals, which form Group 1 in the periodic table.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Can the term 'group' refer to a collection of people?

Yes, in general usage, a group can refer to a collection of people.
Shumaila Saeed
Shumaila Saeed
Feb 16, 2024

Do elements in the same period have the same number of electron shells?

Yes, elements in the same period have the same number of electron shells.
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Shumaila Saeed
Feb 16, 2024

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About Author
Shumaila Saeed
Written by
Shumaila Saeed
Shumaila Saeed, an expert content creator with 6 years of experience, specializes in distilling complex topics into easily digestible comparisons, shining a light on the nuances that both inform and educate readers with clarity and accuracy.

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