Periodic Table Trends

Article with the name “Periodic Table Trends” as the name suggests explores the trends and patterns in the property of elements while arranged in the modern-day periodic table. Scientists in the early days observed that while arranging the elements based on either atomic weight or atomic number, elements with similar properties automatically got arranged closer to each other. This article will explore the same thing with the modern-day lens and will tell you about all the trends in various properties such as atomic radius, valency, metallic or non-metallic characters, reactivity, boiling point, melting point etc. So, let’s learn about these trends in the properties of elements while arranged in the periodic table.

What is Periodic Table?

A periodic Table is the arrangement of all the elements in the known universe based on either atomic weight or atomic number. There are various failed attempts to arrange the known elements so that all the elements with similar properties are arranged together. But in 1863 Russian chemist Dmitri Mendeleev, gave Mendeleev’s Periodic Table which is the most successful attempt of that time. In modern-day, scientists using Mendeleev’s Periodic Table as a base created a long-form periodic table which is called Modern Periodic Table.

In this table, Periods are made up of elements that are organized horizontally (from left to right) and the group is made up of elements that are arranged vertically (from top to bottom). We’ll learn about the periodic trends in these periods and groups in this article.

What are Periodic Trends in Periodic Table?

Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element. They were discovered by the Russian chemist Dmitri Mendeleev in the year 1863. Major periodic trends include atomic radius, ionization energy, electron affinity, electronegativity, valency and metallic character. These trends exist because of the similar electronic configuration of the elements within their respective groups or periods and because of the periodic nature of the elements. These give a qualitative assessment of the properties of each element. Let’s take a look at them in detail,

Atomic Radius

The atomic radius is the distance between an atom’s nucleus and its outermost shell. The periodic trend of atomic radius across a period – Atomic radius steadily lowers as we move from left to right in a period. This is due to the fact that as we move left to right in a period, the atomic number of the elements increases, causing the nuclear charge to increase while the number of shells in elements remains constant. Moving from top to bottom in a group, atomic radii gradually rise as nuclear charge and the number of shells grows.

Exception: Noble gases exhibit extraordinary behaviour. When compared to the preceding halogen atom, the atomic radii of inter gases rapidly increase. The explanation for this unusual behaviour is that in the case of noble gases, atomic radius relates to van der Waal’s radius, whereas in the case of other elements, it refers to the covalent radius.

Valence Electrons 

The electrons in an atom’s outermost shell are referred to as the atom’s valence electrons. The amount of valence electrons grows as we move left to right across a period in the periodic table. Valence electrons remain consistent across a group. It denotes that elements in the same group have the same number of valence electrons. Hydrogen, lithium, and sodium elements, for example, are all found in the first group and all have the same number of valence electrons, which is one. 

Valency  

An atom’s valency is its ability to combine. Moving left to right across a period in the periodic table, valency increases first, then declines. There is no change in valency among members of a group. The valency of elements from the same groups is the same.

Metallic Character of The Elements  

The metallic property of elements reduces as we move left to right across a period in the periodic table. The metallic property of elements grows as we progress up the periodic table from top to bottom.

Non – Metallic Character of The Elements  

The nonmetallic property of elements grows as we move left to right across a period in the periodic table. The non-metallic nature of a group of periodic table elements reduces as we proceed from top to bottom.

Reactivity of Elements

Metal reactivity is determined by its electropositive nature. As a result, the more metallic the element is, the more electropositive it is, and the more reactive it is. As the metallic character decreases from left to right, so does the reactivity. Although the reactivity of nonmetals rises as one moves from left to right over time. As a result, we can deduce that as we move left to right in a period, the reactivity of elements steadily diminishes until group thirteen, when it begins to increase. 

Melting Point

The melting point is the total amount of energy necessary to convert a solid into a liquid. If the link between the atoms of elements is strong, it takes a lot of energy to break the bond. It gets smaller as we go from top to bottom. Non-metals, on the other hand, rise from top to bottom of the periodic table. Among metals, carbon has a high melting point. Boron has a high melting point when compared to other semi-metals. Tungsten has a high melting point when compared to other metals.

Boiling Points of Elements  

Metal boiling points fall gradually from top to bottom in a group. While the boiling temperatures of nonmetals grow from top to bottom in a periodic table group.

Electron Affinity

Electron affinity is the energy released when an electron is added to an atom. As you move from left to right across a period, the electron affinity generally increases. This is because the added electron experiences a greater attractive force from the nucleus as the nuclear charge increases. But there are exceptions to electron affinity trends i.e., noble gases, fluorine, Group 2, Group 14 and Group 15. 

Down a group, the electron affinity generally decreases. This is because as you move down a group, the atomic size increases due to the addition of extra energy levels or shells. With larger atomic size, the outer electrons are farther from the nucleus, resulting in weaker attractive forces between the nucleus and the incoming electron. Therefore, atoms in lower groups have less affinity for an additional electron.

Electronegativity

Electronegativity is a measure of an atom’s ability to attract electrons. As you move from left to right across a period, the electronegativity generally increases. This is because the increased nuclear charge makes the atom more electronegative.

Similar to electron affinity, electronegativity tends to decrease down a group. As you move down a group, the atomic size increases and the valence electrons are located farther from the nucleus. This increased distance reduces the effective nuclear charge experienced by the valence electrons, making it more difficult for the atom to attract additional electrons. Consequently, the electronegativity decreases down the group.

Ionization Enthalpy

Atomic radius shrinks as a period progresses from left to right. As a result, as the size of an atom diminishes, so does the attractive attraction between the nucleus and the outermost electrons. As a result, ionization energy often increases over the periodic table. 

However, when we look at the pattern of ionization enthalpy in groups, we can see that it falls from top to bottom in a group. This is owing to the fact that as the number of shells grows down the group, the outermost electrons will be further away from the nucleus, resulting in a lower effective nuclear charge. Second, the shielding effect increases down the group as the number of shells grows, resulting in a decrease in ionization energy.

Electron Gain Enthalpy

As we move from left to right in a period, the electron gain enthalpy becomes increasingly negative. We can conclude from the patterns of attributes in the periodic table that the elements at the two extremes of the periodic table are most reactive (note: noble gases have entirely filled shells; so they are least reactive) and the elements in the middle are the least reactive. The elements on the extreme left are alkalis, which easily shed electrons to produce cations. 

On the other hand, halogens, the elements on the extreme right that easily gain electrons to create an anion – are present. It is related to the metallic and non-metallic properties of elements whereas while travelling from left to right in a period, metallic properties drop while nonmetallic properties increase. Metallic properties rise in a group while non-metallic properties diminish. In addition, as a period progresses from left to right, metallic features decrease and nonmetallic properties increase. In a group, metallic traits increase while nonmetallic properties decrease.

The below-attached picture shows the general trend in the properties of elements. The direction of arrow shows the increase in property on moving in the direction of arrow.

List of All Periodic Trends

The following table is the summary of all the periodic trends in the properties of different elements.

Property	Across the Period	Down the Group
Atomic Radius	Decreases	Increases
Valence Electrons	Increases	Remains constant
Valency	First Increases then decrease	Remains constant
Metallic Character	Decreases	Increases
Non-Metallic Character	Increases	Decreases
Reactivity	Decreases	Increases after Group 13
Melting Point	Varies (General trend: Decreases for Metals)	Varies (General trend: Increases for Metals)
Boiling Point	Varies (General trend: Decreases for Metals)	Varies (General trend: Increases for Metals)
Ionization Enthalpy	Increases	Decreases
Electron Gain Enthalpy	Increases	Decreases

Read More,

• Periodic Classification of Elements
• Merits of the Modern Periodic Table
• Characteristics of the Periods and Groups of the Periodic Table

Sample Problems on Periodic Table Trends

Question 1: What is meant by the electronic configuration of an element?

Answer: 

An element’s electronic configuration is a symbolic representation of how its atoms’ electrons are arranged across different atomic orbitals. A standardised notation is used for expressing electron configurations, in which the energy level and type of orbital are written first, followed by the number of electrons present in the orbital expressed in superscript.

Question 2: Is it easier to remove an electron from sodium or aluminium?

Answer:

It doesn’t take much energy to extract one electron from a sodium atom in order to generate a Na+ ion with a filled-shell electron configuration. The second aluminium ionisation energy is bigger than the first, and the third is much higher.

Question 3: What is the penetration effect?

Answer:

The proximity of an electron in an orbital to the nucleus is referred to as penetration. It can be viewed as the relative density of electrons near an atom’s nucleus for each shell and subshell. Looking at the radial probability distribution functions, we can see that the electron density of s orbitals is higher than that of p and d orbitals.

Question 4: What is the effect on metallic character as we move in a periodic table?

Answer:

As we advance down the group, the metallic character rises because atomic size increases, resulting in easy electron loss. It, on the other hand, lowers as we move from left to right over time.

Question 5:  What are some metallic characteristics?

Answer:

The qualities associated with the metals contained on the periodic table are referred to as metallic character. These characteristics include metallic shine, hardness, malleability, thermal conductivity, and others.

FAQs on Periodic Table Trends

Q1: What is Periodic Table?

Answer:

The periodic table is a tabular arrangement of chemical elements, organized based on their atomic number, electron configuration, and recurring chemical properties. It provides a comprehensive overview of the elements and their relationships.

Q2: What are Periodic Table Trends?

Answer:

Periodic table trends are regular patterns or trends observed in the properties of elements as you move across a period (horizontal row) or down a group (vertical column) in the periodic table. These trends help us understand the behavior and characteristics of elements.

Q3: What is Atomic Radius?

Answer:

Atomic radius refers to the size of an atom. It is measured as the distance from the nucleus to the outermost electron shell of an atom. Atomic radius generally decreases across a period and increases down a group in the periodic table.

Q4: What is Electronegativity?

Answer:

Electronegativity is the measure of an atom’s ability to attract electrons towards itself in a chemical bond. It indicates the relative strength with which an atom can hold onto its electrons. Electronegativity tends to increase across a period and decrease down a group.

Q5: What is Ionization Energy?

Answer:

Ionization energy is the amount of energy required to remove an electron from a neutral atom and form a positive ion. It is a measure of the atom’s ability to hold onto its electrons. Ionization energy generally increases across a period and decreases down a group.

Q6: What is Electron Affinity?

Answer:

Electron affinity is the energy change that occurs when an atom gains an electron to form a negative ion. It represents the tendency of an atom to accept an electron. Electron affinity generally increases across a period and decreases down a group.

Q7: What is Metallic Character?

Answer:

Metallic character refers to the extent to which an element displays metallic properties such as conductivity, malleability, and luster. Metallic character tends to decrease across a period and increase down a group.

Q8: What is Reactivity?

Answer:

Reactivity refers to the tendency of an element to undergo chemical reactions. It can vary depending on the element’s position in the periodic table. Generally, metals are more reactive on the left side of the periodic table, while nonmetals are more reactive on the right side.

Q9: What are Trends for Melting and Boiling Points on the Periodic Table?

Answer:

Melting and boiling points generally increase across a period and decrease down a group in the periodic table. This trend is primarily influenced by the strength of atomic bonding within the elements.

Q10: What is Trend for Ionic Size on Periodic Table?

Answer:

Ion size generally decreases across a period and increases down a group. Cations (positively charged ions) are smaller than their parent atoms, while anions (negatively charged ions) are larger due to changes in the electron configuration.

Q11: What are Trends for Chemical Reactivity on Periodic Table?

Answer:

Chemical reactivity varies across the periodic table. Generally, metals tend to be more reactive as you move down a group due to the ease of losing electrons. Nonmetals tend to be more reactive as you move up a group because they have a higher tendency to gain electrons.

Q12: What is Trend of Number of Valence Electrons on Periodic Table?

Answer:

Valence electrons are the electrons present in the outermost energy level of an atom. The number of valence electrons generally increases by one from left to right across a period and remains constant within a group (column) in the periodic table.