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A valence electron is an electron in an atom’s outer shell that can participate in the creation of a chemical bond if the outer shell is not closed; in a single covalent connection, both atoms contribute one valence electron to create a shared pair in chemistry and physics.
The existence of valence electrons can affect an element’s chemical characteristics, such as its valence—whether or not it can connect with other elements and, if so, how easily and how many times. In this approach, the reactivity of a particular element is strongly reliant on its electrical arrangement. A valence electron can only reside in the outermost electron shell of a main-group element; a valence electron can also exist in an inner shell of a transition metal.
Chemically, an atom with a closed valence electron shell (equivalent to a noble gas configuration) is inert. The very low energy required to remove the extra valence electrons to generate a positive ion makes atoms with one or two valence electrons more than a closed shell extremely reactive. Due to its inclination to either obtain the missing valence electrons and form a negative ion, or to share valence electrons and create a covalent bond, an atom with one or two electrons fewer than a closed shell is reactive.
A valence electron may receive or release energy in the form of a photon, much like a core electron. Atomic excitation occurs when an energy gain causes an electron to migrate (jump) to an outer shell. Alternatively, the electron can break free from its linked atom’s shell, resulting in ionization and the formation of a positive ion. When an electron loses energy (and hence emits a photon), it might travel to an inner shell that isn’t completely occupied.
Valence Orbitals
An atom has two fundamental components: a nucleus and electrons. An atom’s nucleus is made up of protons and neutrons. The electrons surround the positively charged nucleus. Early atomic models showed electrons in fixed orbits around the nucleus, like planets orbiting the sun.
Theoretically, electrons live in orbitals. An orbital is an area of space where an electron is likely to be found. Orbitals are classified as s, p, d, or f. An s orbital may house two electrons and is spherical. The three p orbitals have the same fundamental dumbbell structure but differ in their spatial orientation. It can contain six electrons.
The d orbitals are more complex than the s and p orbitals. The d orbitals, which may store up to ten electrons, are depicted to the right.
The outermost electrons determine the element’s chemical and physical properties. Valence electrons are the most loosely held electrons and interact with other atoms to create chemical bonds. The valence electrons’ orbital type (s, p, d, or f) depends on the element’s periodic table location. Transition, or d-block, elements, for example, have partly filled d orbitals. These elements employ d orbital electrons for bonding and reactivity.
Orbitals are commonly preceded by numbers, e.g. 4f, 5d, 3p. This value represents the orbital’s size and energy. Greater number denotes greater energy orbital. It is therefore more energetic and farther from the nucleus than electrons in the 2s orbital of lithium (Li).
The seven f orbitals present in lanthanides and actinides are less known than the transition elements. The 14 electrons that potentially occupy these orbitals are strongly constricted (near to the nucleus) and do not appear to overlap with surrounding atoms’ valence orbitals. These orbitals are hypothesized to be important in lanthanide and actinide bonding. As a result, the significance of f orbitals in bonding and reactivity has been hotly debated.
Chemical And Physical Behavior Of The Elements
A physical property is a quality of matter that is unrelated to a chemical change. For example, electrical conductivity and melting and boiling temperatures are physical qualities. Color and density may be detected without affecting the matter’s physical condition. Other physical attributes, like the melting point of iron or the freezing point of water, can only be noticed when matter changes. It is not possible to modify the physical condition or qualities of matter without also changing their chemical identities. Wax melts, sugar dissolves in coffee, and steam condenses into liquid water. Magnetizing and demagnetizing metals (like anti-theft security tags) and powdering solids are some instances of physical changes (which can sometimes yield noticeable changes in color). In each case, the substance’s physical state, shape, or qualities change, but not its chemical makeup.
A chemical reaction always creates new forms of stuff that were not existing before the reaction. Rust is generated by a chemical reaction between iron, oxygen, and water. The nitroglycerin explosion is a chemical change since the gasses created are not the same as the initial material.
Chemical Reactivity
The rate at which a chemical material tends to undergo a chemical reaction over time is referred to as reactivity. The physical features of the sample control reactivity in pure chemicals. Grinding a sample to a greater specific surface area, for example, boosts its reactivity. The presence of impurities in impure substances affects their reactivity as well. The crystalline shape of a chemical can also alter its reactivity. In all circumstances, however, reactivity is essentially owing to the compound’s subatomic characteristics.
Although it is usual to say that substance ‘X is reactive,’ all substances react differently with different reagents. For example, in making the statement that ‘sodium metal is reactive’, we are alluding to the fact that sodium reacts with many common reagents (including pure oxygen, chlorine, hydrochloric acid, water) and/or that it reacts rapidly with such materials at either room temperature or using a Bunsen flame.
The terms stability’ and reactivity’ should not be used interchangeably. After a statistically specified duration, an isolated molecule of an electrically excited state of the oxygen molecule
produces light spontaneously. A species’ half-life is another indicator of its stability, although its reactivity can only be determined through interactions with other species.
Conclusion
The overlap of two independent atomic orbitals on different atoms provides an area with one pair of electrons shared by the two atoms, according to the Valence Bond Theory. A bond is formed when the orbitals overlap along an axis that contains the nuclei.
