Periodic trends are certain patterns that are present in the routine table that show different aspects of a particular element, including its size and its electronic properties. Significant periodic patterns include: electronegativity, ionization energy, electron affinity, atom radius, melting point, and metallic character. Periodic trends, occurring from the arrangement of the routine table, administer sdrta.netists through an invaluable device to easily predict one element"s properties. These fads exist since of the comparable atomic structure of the aspects within their respective group households or periods, and also because of the routine nature that the elements.

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Electronegativity Trends

Electronegativity can be interpreted as a sdrta.netical building describing one atom"s capacity to attract and also bind v electrons. Since electronegativity is a qualitative property, over there is no standardized technique for calculating electronegativity. However, the most common scale for quantifying electronegativity is the Pauling range (Table A2), named after the sdrta.netist Linus Pauling. The number assigned through the Pauling scale are dimensionless as result of the qualitative nature of electronegativity. Electronegativity values for each facet can be uncovered on specific periodic tables. An instance is noted below.

Figure \(\PageIndex1\): regular Table of Electronegativity values

Electronegativity actions an atom"s propensity to entice and form bonds v electrons. This residential property exists due to the electronic configuration the atoms. Most atoms follow the octet preeminence (having the valence, or outer, shell consist of of 8 electrons). Because facets on the left next of the periodic table have actually less 보다 a half-full valence shell, the power required to get electrons is significantly greater compared with the energy required to shed electrons. Together a result, the elements on the left side of the periodic table normally lose electrons when forming bonds. Conversely, aspects on the ideal side that the periodic table are much more energy-efficient in getting electrons to develop a finish valence covering of 8 electrons. The nature the electronegativity is effectively defined thus: the an ext inclined an atom is to acquire electrons, the more likely the atom will certainly pull electrons toward itself.

From left come right throughout a duration of elements, electronegativity increases. If the valence shell of one atom is much less than half full, it calls for less energy to lose an electron than to gain one. Vice versa, if the valence shell is more than fifty percent full, that is easier to pull an electron right into the valence covering than come donate one. From height to bottom under a group, electronegativity decreases. This is because atomic number boosts down a group, and thus over there is an enhanced distance in between the valence electrons and nucleus, or a greater atomic radius. As for the change metals, return they have actually electronegativity values, there is small variance amongst them throughout the period and up and also down a group. This is because their metallic properties affect their ability to attract electrons as quickly as the various other elements.

According to these two general trends, the most electronegative facet is fluorine, through 3.98 Pauling units.

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api/deki/files/1193/Ionization_Energy_Graph_IK.png?revision=1" />Figure \(\PageIndex3\): Graph reflecting the Ionization power of the facets from Hydrogen come Argon

Another factor that affects ionization energy is electron shielding. Electron shielding explains the ability of one atom"s inner electron to shield the positively-charged nucleus from its valence electrons. When relocating to the appropriate of a period, the number of electrons increases and also the toughness of shielding increases. As a result, that is simpler for valence shell electrons to ionize, and also thus the ionization power decreases down a group. Electron shielding is additionally known as screening.


Some aspects have several ionization energies; these varying energies are referred to as the an initial ionization energy, the second ionization energy, 3rd ionization energy, etc. The very first ionization power is the energy requiredto eliminate the outermost, or highest, energy electron, the 2nd ionization energy is the power required come remove any type of subsequent high-energy electron from a gaseous cation, etc. Listed below are the sdrta.netical equations describing the first and 2nd ionization energies:

First Ionization Energy:

\< X_(g) \rightarrow X^+_(g) + e^- \>

Second Ionization Energy:

\< X^+_(g) \rightarrow X^2+_(g) + e^- \>

Generally, any kind of subsequent ionization energies (2nd, 3rd, etc.) follow the same routine trend together the an initial ionization energy.

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Figure \(\PageIndex4\): routine Table reflecting Ionization power Trend

Ionization energies decrease as atomic radii increase. This monitoring is influenced by \(n\) (the primary quantum number) and \(Z_eff\) (based top top the atomic number and also shows how numerous protons space seen in the atom) on the ionization energy (I). The connection is given by the adhering to equation:

\< i = \dfracR_H Z^2_effn^2 \>

throughout a period, \(Z_eff\) increases and n (principal quantum number) remains the same, therefore the ionization power increases. Under a group, \(n\) increases and also \(Z_eff\) increases slightly; the ionization energy decreases.

Electron Affinity Trends

As the name suggests, electron affinity is the capability of one atom to accept an electron. Unlike electronegativity, electron affinity is a quantitative measurement of the energy adjust that occurs as soon as an electron is included to a neutral gas atom. The much more negative the electron affinity value, the greater an atom"s affinity for electrons.

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Figure \(\PageIndex5\): regular Table reflecting Electron Affinity Trend

Electron affinity normally decreases down a group of elements because each atom is bigger than the atom over it (this is the atom radius trend, disputed below). This means that an included electron is additional away from the atom"s nucleus compared with its position in the smaller sized atom. Through a larger distance between the negatively-charged electron and also the positively-charged nucleus, the pressure of attraction is reasonably weaker. Therefore, electron affinity decreases. Moving from left to right across a period, atoms end up being smaller as the pressures of attraction end up being stronger. This reasons the electron to relocate closer come the nucleus, thus increasing the electron affinity from left to right across a period.


Electron affinity rises from left to best within a period. This is caused by the decrease in atom radius. Electron affinity reduce from peak to bottom in ~ a group. This is caused by the increase in atomic radius.

Atomic Radius Trends

The atom radius is one-half the distance in between the nuclei of two atoms (just choose a radius is half the diameter the a circle). However, this idea is complex by the truth that no all atom are usually bound with each other in the very same way. Some room bound through covalent bonds in molecules, some room attracted come each other in ionic crystals, and others are hosted in metallic crystals. Nevertheless, the is possible for a vast majority of facets to type covalent molecules in i m sorry two like atoms are hosted together by a single covalent bond. The covalent radii of these molecules are often referred to as atomic radii. This distance is measure up in picometers. Atomic radius patterns are observed transparent the routine table.

Atomic size progressively decreases from left come right across a period of elements. This is because, in ~ a period or family members of elements, all electrons are added to the exact same shell. However, at the same time, protons are being added to the nucleus, do it more positively charged. The effect of increasing proton number is higher than the of the boosting electron number; therefore, there is a higher nuclear attraction. This way that the nucleus attractive the electrons much more strongly, pulling the atom"s shell closer to the nucleus. The valence electron are organized closer towards the nucleus of the atom. As a result, the atomic radius decreases.

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api/deki/files/1195/Melting_Point_Trend_IK.png?revision=1" />Figure \(\PageIndex7\): chart of melting Points of miscellaneous Elements

Metallic personality Trends

The metallic character of an facet can be identified as how readily an atom have the right to lose one electron. From ideal to left across a period, metallic character increases since the attraction between valence electron and the nucleus is weaker, permitting an much easier loss of electrons. Metallic character boosts as you move down a group because the atomic size is increasing. As soon as the atomic dimension increases, the outer shells space farther away. The major quantum number increases and average electron thickness moves farther native nucleus. The electrons of the valence shell have less attraction to the cell nucleus and, as a result, can lose electrons an ext readily. This causes an increase in metallic character.

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Another easier means to remember the trend of metallic personality is that moving left and also down towards the bottom-left corner of the routine table, metallic character increases toward teams 1 and 2, or the alkali and also alkaline earth metal groups. Likewise, moving up and to the appropriate to the upper-right edge of the periodic table, metallic personality decreases because you room passing by to the right side of the staircase, which suggest the nonmetals. These include the group 8, the noble gases, and also other usual gases such as oxygen and nitrogen.

In other words: relocate left across period and under the group: rise metallic character (heading towards alkali and also alkaline metals) move right across duration and increase the group: diminish metallic personality (heading towards nonmetals like noble gases)Metallic Character tendency IK.pngdoes atomic radius increase from top to bottom