It is a yellow-white volatile solid soluble in water. In this article, we will understand the basic concepts required to predict Lewis structure, geometry, hybridization, and polarity of a given substance.
Lewis Structure
Lewis Structure
Lewis structure is a 2D representation of the arrangement of atoms in a compound. It shows the arrangement of electrons around individual atoms. According to Lewis, only valence electrons participate in bond formation, and hence only valence electrons are represented in Lewis symbols. One compound can have more than one possible Lewis structure. We look for the structure that satisfies the octet rule and formal charges in such cases.
Octet Rule
Octet Rule
All the atoms of the main group elements prefer to have eight valence electrons (except period1 elements) to attain stability. This preference for eight electrons is called the octet rule. Group 18 elements are considered most stable and have 8 valence electrons (except He). Thus, elements of other groups prefer 8 valence electrons to have noble gas-like stability.
The octet rule is important for a stable Lewis structure, but many compounds can never follow the octet rule but are stable. Octet rule does not explain the stability of- • Hypovalent compounds- central atom is electron-deficient, and its octet can never be completed. For example, AlCl3, etc. • Hypervalent compounds- central atom is electron-rich due to the expansion of octets and has more than 8 valence electrons on the central atom. For example, SF6, etc. • Odd electron species- some molecules have odd electrons and can never achieve octet as they cannot have an even number of electrons. For example, NO, etc.
Formal Charge
Formal Charge
It is a theoretical concept. It compares the electrons present on an isolated neutral atom with the electrons present on the atom in the compound. The formula for the formal Charge is Formal Charge = (total number of valence shell electrons in an isolated atom) – (number of nonbonded electrons)- 0.5*(number of electrons involved in bond formation) A negative formal charge is more stable on an electronegative atom than on an electropositive atom and vice-versa. Steps for drawing Lewis structure for a given compound
SeCl4 Geometry
SeCl4 Geometry
Molecular geometry refers to the 3D arrangement of atoms of a molecule in space. VSEPR theory helps in determining the shape and geometry of a given compound. VSEPR theory stands for valence shell electron pair repulsion theory. This theory is based on the principle that the valence shell electrons of each atom in a molecule arrange themselves in such a way that the inter-electronic repulsion is minimum, and the arrangement becomes stable. The stable arrangement is called geometry. Geometry and shape are often confused with each other. Geometry refers to the arrangement of bond pair of electrons, while shape refers to the arrangement of bond pair and lone pair of electrons.
How To Predict SeCl4 Geometry Using VSEPR
SeCl4 Hybridization
SeCl4 Hybridization
Hybridization is one of the fundamental concepts used to explain bond formation. Hybridization involves mixing two or more atomic orbitals with comparative energy, size, and shape to form orbitals with the same energy, shape, and size. The hybridized orbitals form bonds, and the extent of overlap is better than unhybridized orbitals. For example, one 4s and one 4p can form two sp hybrid orbitals, but 4s and 8d cannot.
In SeCl4, Se is the central atom. We are focusing on the hybridization of the central atom only. In the ground state, Se has 2 unpaired electrons. It can only form two bonds. Promotion of electrons takes place from 4p to 4d, and 4 valence electrons become unpaired.
Steric Number Method
The steric number refers to the total number of electron pairs on the central atom. For SeCl4, electron pairs=5 (shown while prediction of geometry using VSEPR) Also, Steric number = number of (sigma bonds +lone pair on central atom) Steric number for SeCl4= (4+1)=5 Hybridization comes out to be sp3d from the table.
SeCl4 Polarity
SeCl4 Polarity
A compound is polar if it has a non-zero net dipole moment and non-polar if the net dipole moment is zero. The exact value of net dipole moment can be found by vector addition of dipole moment of all the bonds in a molecule. The dipole moment of a bond can be calculated using the formula Dipole moment = charge* distance of separation between the charges We need not calculate the exact value of dipole moment to determine polarity but can do a qualitative assessment of the compound for the same. The dipole moment of a compound depends on • Dipole moment, which in turn depends on the difference between the electronegativities of atom forming bonds. • Geometry of compound In SeCl4, only one type of bond is formed: ‘ Se-Cl’. The electronegativity of Se and Cl is 2.55 and 3.16, respectively. The difference comes out to be 0.61. Thus, the bonds are polar. Polar bonds do not guarantee a polar molecule. We consider the geometry and symmetry of the compound as well. The shape is a see-saw, and the bond vectors do not cancel each other out. Thus, the compound is polar.
Related Topics CH2Br2 Lewis Structure CHF3 Lewis Structure H2Se Lewis Structure SeOCl2 Lewis Structure SeF6 Lewis Structure XeOF4 Lewis Structure AlCl3 Lewis Structure CH3CN Lewis Structure SeF4 Lewis Structure Cl2 Lewis Structure AsH3 Lewis Structure
Conclusion
Selenium tetrachloride is a covalent compound. The Lewis structure drawn in the above sections is the most suitable. Se expands its octet and is a hyper-valent compound. The geometry of the compound is trigonal pyramidal, and the shape is a see-saw. The hybridization of the central atom is sp3d. It is a polar compound. Happy Reading!
