Periodic Trends in Physical Properties
The systematic arrangement of elements in a periodic table reveals some periodic tendencies in element properties. Atomic and ionic radii, for example, decrease from left to right in a period. Understanding the patterns in fundamental properties of elements (atomic and ionic radii, ionization enthalpy, and electron gain enthalpy) will lead you to the conclusion that periodicity in properties is mostly determined by an element’s electronic configuration. We can discover a relationship between chemical properties and fundamental qualities of elements after thoroughly researching the concepts.
Period and Group
- Periods are elements that are organized horizontally (from left to right).
- A group is made up of elements that are arranged vertically (from top to bottom).
Periodic Trends in Physical Properties
There are different trends in physical properties, for instance, atomic radius, valence electrons, melting point, boiling point, ionization enthalpy, and so on. 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 behavior. When compared to the preceding halogen atom, the atomic radii of inter gases rapidly increase. The explanation for this unusual behavior 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 nonmetallic 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.
- 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. And traveling 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.
Sample Problems
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 aluminum?
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.
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