Поделиться
Урок 13.docx
Lesson-lecture on " Hybridization of atomic orbitals. Geometry of molecules" - structure of MATTER - LESSON PLANS for CHEMISTRY 11 class - lesson plans-lesson plans-author's lessons-plan-lesson summary - chemistry
The purpose of the lesson: to generalize and systematize knowledge about the types of hybridization of atomic orbitals in organic compounds; to teach how to apply this knowledge to explain hybridization in inorganic compounds, to consolidate knowledge of the dependence of the geometry of particle molecules on the type of hybridization.
Equipment: table "Structure of the carbon atom", "the Structure of methane, ethane, - giant", totransparency.
Basic concepts: hybridization, types of hybridization, geometry of molecules, particles; algorithms for determining the type of hybridization and geometry of particles of molecules.
Lesson progress
I. Organizational moment
The teacher informs students of the results of previous independent work, analyzes mistakes made in the tasks, and explains the correctness of their execution. Then there is a smooth transition to a new topic.
II. Learning new material
We have studied the main types of chemical bonds and types of crystal lattices. Let us ask ourselves the following problem: how do the molecules of many compounds have a polar covalent bond, and the molecule itself is nonpolar? For example WITH2, the dipole moment is equal to 0, and the space located at an angle of 180 °, why is the water molecule dipole moment is 6.1 · 10-30and relationships located in space at a certain angle of 104.5 °; in the molecule, CH4 is methane, a covalent polar bond and the molecule is nonpolar.
It turns out that one of the reasons is the hybridization of atomic orbitals and the formation of a valence angle during a certain type of hybridization.
The concept of "hybridization" was introduced in the course "Organic chemistry" in the 10th grade when studying the valence States of the carbon atom.
What is hybridization? Alignment of the electron density of atomic orbitals by energy and shape. AO become identical, as a result of which equivalent bonds with other atoms are formed and their maximum distance from each other in space is achieved. There are three possible types of hybridization in a carbon atom: sp3-; sp2-; sp-. Elements of the second period tend to hybridize the most. To determine the type of hybridization we use the algorithm (on totransparency).
Algorithm for determining the type of hybridization and geometry of a molecule or particle
|
Sequential steps for determining the type of hybridization |
Example |
|
1) Determining the number of Unpaired elements in a compound. the Number of unpaired electrons in the Central atom |
H2+1O-2 C. O C. O(O) = -2 ⇒× in atom 0 two unpaired electrons |
|
2) Determining the coordination number of the Central atom (how many other atoms it holds about itself). The coordination number corresponds to the number of σ-bonds |
K bonds.h.(About) = 2 in the 2σ-bond molecule O +8; 1s22s22p4 |
|
3) Building a graphical formula for the Central atom |
|
|
4) On this model, we separate as many orbitals with unpaired electrons , as well as free atomic orbitals, as there are σ -bonds. We start with the s-orbital and determine the type of hybridization
|
the hybridization involves orbitals of energy level II s - (a pair of paired electrons) and 3p - (one pair of paired electrons and two unpaired ones) |
|
5) based on the type of hybridization, we place all hybrid orbitals in space symmetrically relative to the nucleus of the atom:
|
sp3-hybridization 109°28'; 4-hybrid orbitals
|
|
6) Determine the geometry of the molecule, particle sp3-hybridization: 4σ-connections — tetrahedron; 3σ-connections-trigonal pyramid; 2σ-connections-angular: 1σ-connection-linear; sp2-hybridization: 3σ-connections-triangular flat; 2σ-connections-angular; 1σ-connection-linear: sp-hybridization: σ-connection-linear |
In this diagram, we clearly distinguish as many directions of hybrid orbitalsas a-bonds, since in the molecule 2σ-bonds, we distinguish two orbitals
However, the binding angle is 104.5°, not 109°28'. for example, an.кoxygen atom has two pairs of paired electrons in hybrid orbitals, resulting in an increased electron density that reduces the hybridization angle to 104.5° |
It should be remembered that the σ-link always has a direction in space, localized; the l-link does not have a direction in space, nor does the localized link. So, we found out: how to determine the type of hybridization and geometry of a particle or molecule according to the algorithm; орбиталиthe s-, p - and d - orbitals are involved in hybridizationорбитали.
III. Homework assignment
§ 7 # 3-determine geometry and hybridization by algorithm, # 4-explain conclusions based on hybridization and geometry of molecules; repeat § 6, prepare for the lesson of generalizing repetition.
IV. Consolidation
Task; determine the type of hybridization and geometry of molecules:
a) SiCl4; b) BF3; C) Sicl2;
Be in the form of a table.
|
There are only two unpaired electrons in the atom, and you need four, and 2s electrons are steamed together in the atom
In the excited state — four unpaired electrons, since 4 σ-bonds; we separate four orbitals, sp3-hybridization, angle 109°28'; four hybrid orbitals, since 4σ-bonds |
One unpaired electron, and you need three. In the boron atom there is a steaming of 2s electrons
Boron in the excited state — three unpaired electrons, since 3σ-bonds: we separate the three orbitals. sp2-hybridization; three hybrid orbitals, angle 120° |
There are no unpaired electrons, and you need two, there is a steaming of 2s electrons
In the excited state, there are two unpaired electrons in the boron atom, we separate the two orbitals, since 2σ-bonds, two hybrid orbitals are formed, the angle is 180° |
|
The molecular geometry
tetrahedral shape of the molecules
|
The geometry of molecules
is a flat triangle
|
The geometry of molecules
is linear
|
Материалы на данной страницы взяты из открытых источников либо размещены пользователем в соответствии с договором-офертой сайта. Вы можете сообщить о нарушении.
