The modern periodic law states that the physical and chemical properties of elements are periode functions of their atomic numbers. This means elements with similar properties appear at regular interv when arranged by increasing atomic number
modern periodic table is arranged in order of increasing atomic numbers. Elements organized into rows called periods and columns called groups. Elements in the same group share chemical properties, while periods indicate the number of electron shells.
There are 7 periods and 18 groups in the modern periodic table. Perlods are horizontal rows, and they represent the number of electron shells in atoms. Groups are vertical columns, and elements in same group have the same number of valence electrons.
A group is a vertical column in the periodic table containing elements with the same number of valence electrons. For example, Group 1 elements all have one valence electron and exhibit simi chemical properties, like reacting with water to form basic solutions.
Elements in the same group have the same number of valence electrons, which determine how they bond with other elements. For example, alkali metals in Group 1 have one valence electron, maling them highly reactive and giving them similar chemical behavior.
The period number indicates the number of electron shells in an atom of the element. For example, elements in Period 2, like lithium and fluorine, have two electron shells, while those in Period 3, like sodium, have three electron shells.
Group 1 elements are called alkali metals, including lithium (Li), sodium (Na), and potassium (K They are highly reactive metals with one valence electron, making them good conductors of electricks and quick to react with water.
Noble gases are found in Group 18 of the periodic table. These include helium (He), neon (Ne). and argon (Ar). They are unreactive because they have a full outer shell of electrons, making them stable and chemically inert.
Metallic character decreases across a period as elements become less likely to lose electrons. This Ans because the thiefective nuclear charge increases, pulling electrons closest to lose harder to lose
The number of valence electrons increases from left to right across a period. For example, in Period 2, lithium has 1 valence electron, carbon has 4, and fluorine has 7. This trend explains the gradual change in chemical properties across a period.
Group 1 elements form +1 ions because they lose one electron to achieve a stable configuration For example, sodium (Na) loses one electron to form Na", achieving the stable configuration of neon.
Group 17 elements form-1 ions because they gain one electron to complete their outermost shell. For example, chlorine (CI) gains one electron to form Cl, achieving the stable configuration of argon
Group 2 elements, also called alkaline earth metals, form +2 ions by losing two valence electrons For example, magnesium (Mg) loses two electrons to form Mg.
For elements in Groups 1-2 and 13-18, the group number corresponds to the number of valence electrons. For example, Group 15 elements like nitrogen have 5 valence electrons, while Group
Noble gases already have a full outer shell of electrons, making them stable and unreactive. They do not tend to gain or lose electrons, so they rarely form ions or participate in chemical reactions.
Atomic size decreases across a period because the number of protons in the nucleus increases, pulling the electrons closer. For example, fluorine has a smaller atomic radius than lithium, even though both are in Period 2.
Atomic size increases down a group due to the addition of electron shells. For instance, cesium in Group 1 is much larger than lithium because cesium has six more electron shells.
Cesium (Cs), found in Group 1 and Period 6, has the largest atomic size. This is because it has many electron shells, and the outermost electrons are far from the nucleus.
Atomic radii increase consistently down a group because additional electron shells are added, even though the elements have the same number of valence electrons. :
Infini yonization energy is the energy required to remove the outermost electron from a neutral atom It reflects how tightly an atom holds onto its electrons and is higher in non-metals than in metals
lonization energy increases across a period because the nuclear charge increases, making it harder Ansonitations, For example, fluorine has a higher ionization energy than lithium in Period 2
ionization energy decrease down a group because the outermost electrons are farther from the nucleus and experience less attraction, making them easier to remove.
Helium (He) has the highest ionization energy because its electrons are very close to the nucleus, and the small atomic size increases the attraction between the nucleus and electrons.
Metals have low ionization energy because they tend to lose electrons easily to achieve a stable electron configuration. This property makes them good conductors of electricity.
Electron affinity is the energy change that occurs when an atom gains an electron to form a negative ion. Non-metals, like chlorine and oxygen, have high electron affinities because they strongly attract electrons.
Fluorine (F) has the highest electronegativity because it strongly attracts electrons to fill its auter shell. This makes it the most reactive non-metal in the periodic table.
Metallic character increases down a group because atoms more easily lose their valence electrons due to reduced nuclear attraction. For example, cesium is more metallic than lithium.
Non-metals are more electronegative because they have a strong tendency to attract electrons to complete their outer shell, unlike metals, which tend to lose electrons.
Density generally increases down a group as the atomic mass increases, while atomic size does not expand proportionally. For example, elements like gold and osmium are extremely dense due to their high atomic mass.
