CH3CH3?Bond Angle? Molecular Geometry? Hybridization? Polar Or Non-polar?

What Is CH3CH3?

CH3CH3 is a hydrocarbon compound with the molecular formula of C2H6. It is also referred to as Ethane and is a colorless and non-odorous gas at temperatures of room temperature and pressure. Ethane is an ionic molecule that has a tetrahedral structure. This means it comprises four identical C-H bonds and two carbon atoms joined through a single bond.

Ethane is a colorless, smell-less, gaseous hydrocarbon (a compound made up of carbon, hydrogen, and carbon) that is part of the paraffin series. Its chemical formula is C2H6. It is the simplest structural hydrocarbon, which has only one carbon-carbon bond. The second-most important element in natural gas is that it can also be found as a dissolved substance within the oil and petroleum oils and is a by-product of oil refinery operations and coal’s carbonization process.

The Importance Of Ethane 

The importance of Ethane in the industrial world is due to the ease at which it can be transformed into the chemical ethylene (C2H4) or hydrogen through pyrolysis or cracking after passing via a hot tube. Much like propane and in lesser amounts of butane, Ethane is the main raw material used in the massive ethylene petrochemical business, which creates essential products such as polyethylene plastic, glycol, and ethyl ethanol.

Over 90% of the Ethane produced during the 1960s was used as fuel, but it was not separated from natural gas. It is believed that ethane gas can be liquefied under pressure or at lower temperatures and, consequently, separate from natural gas. Like propane, liquid Ethane is not used as a domestic or industrial fuel.

Bond Angle Of CH3CH3

The bond angle in CH3CH3, also referred to as Ethane, is an important characteristic of the chemical. Knowing how the angle of the bonds is essential in determining a compound’s physical and chemical characteristics, including its reactivity, boiling point, and polarity. This article will review the CH3CH3 bond angles, their significance, and the variables that influence the angle.

Bond Angle of CH3CH3

Its bond angle CH3CH3 refers to the angle between two C-H bonds of the same carbon atom within the molecule. For example, carbon-carbon bond angle of the ethane molecule is 109.5 degrees, which is similar to the tetrahedral bond angle. The angle is the result of electron pairs formed on carbon atoms that repel one another, push the molecules away from each other, and create the tetrahedral shape.

The angle between the C-H bonds of CH3CH3 can also be described as tetrahedral, which means it is that angle of C-H bonds on every carbon atom measures 109.5 degrees. This angle is perfect for an efficient pack of ethane molecules within the solid state. It additionally allows the molecule to be in a symmetrical manner. The structure of Ethane’s symmetry is vital as it influences the dipole moment of the molecule as well as its reactivity and boiling point.

Significance Of Bond Angle

The bond angle in the molecule is a significant element that determines the chemical and physical properties. The bond’s angle affects the molecule’s polarity direction, which impacts its solubility and boiling point. Ethane’s bond angle ofe of 109.5 degrees leads to an unpopular molecule without a net dipole. This results in Ethane being a unipolar solvent, and the reason it isn’t water-soluble.

The bond angle can also influence the reactivity of molecules. In the case of Ethane, the tetrahedral bond angles allow an efficient overlap of hydrogen and carbon orbitals, which makes them more reactive than molecules with lower bond angles, like alkenes. Tetrahedral geometry also permits Ethane to move around the carbon-carbon bond. This is crucial to its stability and reactivity.

Factors Affecting Bond Angle

The bond angle of molecules is influenced by various factors, including the number of pairs of electrons and the electronegativity atoms, as well as the hindrance caused by steric. For CH3CH3, this angle will be affected by the number of electron pairs on carbon atoms and the steric hindrance caused through the methyl group.

The electron pairs on carbon atoms of CH3CH3 oppose each other and push the carbon atoms further away, creating a tetrahedral shape with an angle of 109.5 degrees. In addition, the steric hindrance induced through the methyl group alters the bond angle, pulling hydrogen atoms closer and decreasing the bond angle.

In the end, the bond angle for CH3CH3, also known as Ethane, is 109.5 degrees, the same as the tetrahedral bond angle. The angle is the result of electron pairs formed by carbon atoms. It is the ideal angle for efficiently packing ethane molecules into their solid form. The bond angle can also influence its polarity and reactivity and the point at which the boiling occurs of the molecules. The factors that affect the bond angle are

The Molecular Geometry of CH3CH3

If molecules are covalently bound, the molecules have an ideal geometrical structure (as predicted by the valence bond theory). This arrangement of geometrical shapes concentrates the charge density within the binding region and ensures that the nuclei are as far from each other as possible.

If a molecule contains multiple bonds, the molecular geometry of the molecule is to be considered to determine if it is non-polar or polar. This is determined by the arrangement of the bonds and the lone pairs surrounding the carbon atom at the center.

Molecular Geometry

Molecular geometry refers to the three-dimensional structure of the atoms which compose the molecule. It’s often a crucial element in determining molecules’ physical and chemical properties. For example, the molecular shape of specific molecules may affect their reactivity and solubility.

The Factors That Affect Molecular Geometry

There are a variety of elements that affect molecular geometry, which include the number of lone pairs and bonding between the atoms. These variables can affect the structure of molecules.

The repulsion between electrons of the valence on an atom may also be a factor in the design of the molecule. It is known as the valence-shelf electron pair repulsion theory, also called VSEPR short. The theory predicts the 3-dimensional structure of molecules by studying the repulsion between the two electrons – lone electrons and the valence electrons within a molecule.

A molecule with 6 electrons and two lone pairs will exhibit an equilateral planar structure. The most typical kind of molecule that you’ll find in your studies. It is essential to note that the types as mentioned above of molecules also can adopt an angular or trigonoplanar structure based on the bond types and atoms found within the molecules.

The shape of a molecule may be determined by the number of bonds it has and if these bonds are polar or not. A polar molecule has electric poles on the opposite side of the molecules. This may make the molecule have the highest surface tension and makes it easier to dissolve other materials.

As an example, the molecular shape that water has is known as a Tetrahedral shape since it has four electrons that are bonded and two lone pairs that are not shared. It is also composed of six and two polar bonds, making it a polar molecule.

The study of molecular geometry can be done by studying the physical properties of the molecules or employing techniques for spectroscopy. For example, they can be used to study IR microwave, IR, and Raman spectroscopy. In addition, X-ray crystallography electron diffraction and neutron diffraction are other methods that can provide you with more details on molecules’ structure and molecular makeup.

If you’re studying molecular geometry, it’s crucial to comprehend how lone pairs and bonded electrons influence the repulsion between molecule atoms. If you understand how lone pairs and bonded electrons get repelled by one another, understand the bond angles between the atoms within molecules.

The attraction between electrons of the valence within an atom defines the bonds. They change according to how many lone pairs or bonds are present within a particular molecule. This is why it’s essential to know about the VSEPR theory. (VSEPR) concept.

Molecular geometry can be explored with the aid of Lewis structures. Here, you can see the atoms and single electrons that connect to one another in a 3D model. This visualization is beneficial in determining the proper structure of your molecules.

Hybridization

It is called hybridization if two orbitals from atomic physics are combined to create the hybrid orbital of atomic particles. This expansion of the valence bond theory affects molecular geometry and bonding properties. Hybridization is generally performed by atomic orbitals that have similar energy levels. However, it could occur with fully-filled or half-filled atomic orbitals.

The fundamental idea is that orbitals of atomic nature mix to create new atomic orbitals, which may contain the same amount of electrons as original orbitals in the atomic scale. The fusion of orbitals of atomic nature could result in completely different forms, energy levels, and more.

In the most basic case of hybridization, carbon atoms can utilize their three orbitals with p-type occupied singly.

Sp3 

Another kind of hybridization is sp3, where three p orbitals join to form a hybrid orbital. The hybrid orbitals are characterized by trigonal symmetry and form an angle of 120 degrees with one the other.

This can result in a tetrahedral arrangement of bonds, which we observed in methane and ethylene. This is also apparent in phosphorus pentachloride. This contains 5 Sp3 hybridized orbitals with equal energy and is distinguished by its trigonometric bipyramidal form.

The Hybrid Orbitals

The hybrid orbitals are aligned at an angle of 120 degrees toward each other and are on the horizontal plane. The two remaining orbitals are situated at 90-degree angles to the hybrid orbits of the equatorial and are located in the vertical plane.

The hybridized orbitals of sp3 have the same number of characters for s and p, like those of the original orbitals, while the sp2 hybridized orbitals are like SP orbitals. However, they don’t contain as many s or characters as the original ones.

Sp3 Hybridization

In the event of the sp3 hybridization process, we can expect every carbon atom to possess four carbon-hydrogen bonds, which will be a tetrahedral arrangement of bonds. The C-H-C and H-C-H angle of bonds is similar to 109.5 degrees, while the Acid (OH) group’s bond to carbon atoms will be at the angle of 109.5 degrees.

The sp3 hybridized atoms could be polar or non-polar dependent on the chemical interactions between the C-C and C-H bonds. The sp3 atoms will exhibit an increased bond-bond electrostatic attraction between the two C-C sigma bonds than between those two C-H bonds. This repulsion could cause the bond angles to widen and close from their 120deg ideal angles to reduce the resistance force.

Polar Or Non-polar?

The polarity of a molecule refers to the number of electric charges around it. The electronegativity of the atoms within the bonds determines this. Therefore, a molecule that distributes electrons equally between its atoms is considered non-polar, and a molecule with significant differences in electronegativity can be classified as not polar.

The primary distinction between polar and bonds that are not polar is the fact elements in polar bonds are attracted to the shared electrons differently. The molecule is therefore characterized by dipole energy which results in one end of the molecule possessing negative charges (d-) while the other has positive charges (d+).

A non-polar covalent bond will have the same proportion of electrons in the atoms. This is partly due to the atoms’ electronegativity levels, which indicates the degree to which they are attracted to the same pair of electrons.

Electronegativity

However, bonds with different electronegativity levels can be polar if the element with the highest electronegativity isn’t associated with any electronegative element. A molecule, for instance, composed of two chlorine atoms, C2H4, is a covalent, polar bond since the carbon atom draws more electrons away from the chlorine atom than the chlorine atom.

Another crucial aspect to consider when deciding if a molecule is polar molecular geometry. This refers to the molecule’s shape and the size and position of its molecules atoms. For example, carbon dioxide can be described as a linear molecule with two polar bonds. In contrast, water is a bent structure. An extremely high electronegativity. Oxygen atoms draw charges away from carbon atoms.

Because there is no underlying symmetry in the molecules, the individual dipoles of bonds cannot cancel each other out, and the total molecular polarity is zero. If a molecule is more complex, like the boron trifluoride (BF3), the trigonal configuration of the three bonds leads to the absence of a general dipole.

The Carbon-Oxygen Double Bond 

Found in formaldehyde (methanal) as well as the carbon-nitrogen triple bond of Acetonitrile (cyano methane) are covalent bonds that are both polar. This is because the elements that are more electronegative within these bonds take electrons from carbon atoms, making them less appealing compared to the elements with lower electronegative.

In addition, the polarity of molecules is usually affected by the interactions with their polar bond with other polar molecules. This is referred to as the dipole-dipole interplay. It is less effective than metallic, ionic, or covalent bonds. However, it is responsible for the general polarity of a molecule.

To understand the concept of a polar bond, it’s important to understand how it functions. When a polar bonds, one atom pulls on the electron pair shared by the other more strongly than another, resulting in dipole moments. This creates areas that are partially positive and negative charges, which can create interesting interactions between molecules.

FAQ’s

Describe CH3CH3.

Ethane, a colourless and odourless gas that is frequently used as fuel, has the chemical formula CH3CH3.

What is the CH3CH3 bond angle?

In CH3CH3, the bond angle is 109.5 degrees.

What is the CH3CH3’s molecular geometry?

Each carbon atom in CH3CH3 is coupled to four other atoms in a tetrahedral arrangement, giving the compound a tetrahedral molecular geometry.

What does CH3CH3 hybridization entail?

In CH3CH3, the carbon atoms are sp3 hybridised. It follows that each carbon atom has four orbitals, each of which can be used to create four covalent bonds with other atoms.

How polar or nonpolar is CH3CH3?

A non-polar molecule is CH3CH3. As the electrons in covalent bonds are equally distributed among the atoms due to the electronegativity of carbon and hydrogen, there is no net dipole moment.

What are some typical applications for CH3CH3?

The primary uses of ethane are as a fuel for cooking and heating as well as as a starting point for the synthesis of compounds like ethylene and polyethylene. Moreover, it serves as a propellant in aerosol sprays and a refrigerant.

 

 

CH3CH3?Bond Angle? Molecular Geometry? Hybridization? Polar Or Non-polar?

What Is CH3CH3?

CH3CH3 is a hydrocarbon compound with the molecular formula of C2H6. It is also referred to as Ethane and is a colorless and non-odorous gas at temperatures of room temperature and pressure. Ethane is an ionic molecule that has a tetrahedral structure. This means it comprises four identical C-H bonds and two carbon atoms joined through a single bond.

Ethane is a colorless, smell-less, gaseous hydrocarbon (a compound made up of carbon, hydrogen, and carbon) that is part of the paraffin series. Its chemical formula is C2H6. It is the simplest structural hydrocarbon, which has only one carbon-carbon bond. The second-most important element in natural gas is that it can also be found as a dissolved substance within the oil and petroleum oils and is a by-product of oil refinery operations and coal’s carbonization process.

The Importance Of Ethane 

The importance of Ethane in the industrial world is due to the ease at which it can be transformed into the chemical ethylene (C2H4) or hydrogen through pyrolysis or cracking after passing via a hot tube. Much like propane and in lesser amounts of butane, Ethane is the main raw material used in the massive ethylene petrochemical business, which creates essential products such as polyethylene plastic, glycol, and ethyl ethanol.

Over 90% of the Ethane produced during the 1960s was used as fuel, but it was not separated from natural gas. It is believed that ethane gas can be liquefied under pressure or at lower temperatures and, consequently, separate from natural gas. Like propane, liquid Ethane is not used as a domestic or industrial fuel.

Bond Angle Of CH3CH3

The bond angle in CH3CH3, also referred to as Ethane, is an important characteristic of the chemical. Knowing how the angle of the bonds is essential in determining a compound’s physical and chemical characteristics, including its reactivity, boiling point, and polarity. This article will review the CH3CH3 bond angles, their significance, and the variables that influence the angle.

Bond Angle of CH3CH3

Its bond angle CH3CH3 refers to the angle between two C-H bonds of the same carbon atom within the molecule. For example, carbon-carbon bond angle of the ethane molecule is 109.5 degrees, which is similar to the tetrahedral bond angle. The angle is the result of electron pairs formed on carbon atoms that repel one another, push the molecules away from each other, and create the tetrahedral shape.

The angle between the C-H bonds of CH3CH3 can also be described as tetrahedral, which means it is that angle of C-H bonds on every carbon atom measures 109.5 degrees. This angle is perfect for an efficient pack of ethane molecules within the solid state. It additionally allows the molecule to be in a symmetrical manner. The structure of Ethane’s symmetry is vital as it influences the dipole moment of the molecule as well as its reactivity and boiling point.

Significance Of Bond Angle

The bond angle in the molecule is a significant element that determines the chemical and physical properties. The bond’s angle affects the molecule’s polarity direction, which impacts its solubility and boiling point. Ethane’s bond angle ofe of 109.5 degrees leads to an unpopular molecule without a net dipole. This results in Ethane being a unipolar solvent, and the reason it isn’t water-soluble.

The bond angle can also influence the reactivity of molecules. In the case of Ethane, the tetrahedral bond angles allow an efficient overlap of hydrogen and carbon orbitals, which makes them more reactive than molecules with lower bond angles, like alkenes. Tetrahedral geometry also permits Ethane to move around the carbon-carbon bond. This is crucial to its stability and reactivity.

Factors Affecting Bond Angle

The bond angle of molecules is influenced by various factors, including the number of pairs of electrons and the electronegativity atoms, as well as the hindrance caused by steric. For CH3CH3, this angle will be affected by the number of electron pairs on carbon atoms and the steric hindrance caused through the methyl group.

The electron pairs on carbon atoms of CH3CH3 oppose each other and push the carbon atoms further away, creating a tetrahedral shape with an angle of 109.5 degrees. In addition, the steric hindrance induced through the methyl group alters the bond angle, pulling hydrogen atoms closer and decreasing the bond angle.

In the end, the bond angle for CH3CH3, also known as Ethane, is 109.5 degrees, the same as the tetrahedral bond angle. The angle is the result of electron pairs formed by carbon atoms. It is the ideal angle for efficiently packing ethane molecules into their solid form. The bond angle can also influence its polarity and reactivity and the point at which the boiling occurs of the molecules. The factors that affect the bond angle are

The Molecular Geometry of CH3CH3

If molecules are covalently bound, the molecules have an ideal geometrical structure (as predicted by the valence bond theory). This arrangement of geometrical shapes concentrates the charge density within the binding region and ensures that the nuclei are as far from each other as possible.

If a molecule contains multiple bonds, the molecular geometry of the molecule is to be considered to determine if it is non-polar or polar. This is determined by the arrangement of the bonds and the lone pairs surrounding the carbon atom at the center.

Molecular Geometry

Molecular geometry refers to the three-dimensional structure of the atoms which compose the molecule. It’s often a crucial element in determining molecules’ physical and chemical properties. For example, the molecular shape of specific molecules may affect their reactivity and solubility.

The Factors That Affect Molecular Geometry

There are a variety of elements that affect molecular geometry, which include the number of lone pairs and bonding between the atoms. These variables can affect the structure of molecules.

The repulsion between electrons of the valence on an atom may also be a factor in the design of the molecule. It is known as the valence-shelf electron pair repulsion theory, also called VSEPR short. The theory predicts the 3-dimensional structure of molecules by studying the repulsion between the two electrons – lone electrons and the valence electrons within a molecule.

A molecule with 6 electrons and two lone pairs will exhibit an equilateral planar structure. The most typical kind of molecule that you’ll find in your studies. It is essential to note that the types as mentioned above of molecules also can adopt an angular or trigonoplanar structure based on the bond types and atoms found within the molecules.

The shape of a molecule may be determined by the number of bonds it has and if these bonds are polar or not. A polar molecule has electric poles on the opposite side of the molecules. This may make the molecule have the highest surface tension and makes it easier to dissolve other materials.

As an example, the molecular shape that water has is known as a Tetrahedral shape since it has four electrons that are bonded and two lone pairs that are not shared. It is also composed of six and two polar bonds, making it a polar molecule.

The study of molecular geometry can be done by studying the physical properties of the molecules or employing techniques for spectroscopy. For example, they can be used to study IR microwave, IR, and Raman spectroscopy. In addition, X-ray crystallography electron diffraction and neutron diffraction are other methods that can provide you with more details on molecules’ structure and molecular makeup.

If you’re studying molecular geometry, it’s crucial to comprehend how lone pairs and bonded electrons influence the repulsion between molecule atoms. If you understand how lone pairs and bonded electrons get repelled by one another, understand the bond angles between the atoms within molecules.

The attraction between electrons of the valence within an atom defines the bonds. They change according to how many lone pairs or bonds are present within a particular molecule. This is why it’s essential to know about the VSEPR theory. (VSEPR) concept.

Molecular geometry can be explored with the aid of Lewis structures. Here, you can see the atoms and single electrons that connect to one another in a 3D model. This visualization is beneficial in determining the proper structure of your molecules.

Hybridization

It is called hybridization if two orbitals from atomic physics are combined to create the hybrid orbital of atomic particles. This expansion of the valence bond theory affects molecular geometry and bonding properties. Hybridization is generally performed by atomic orbitals that have similar energy levels. However, it could occur with fully-filled or half-filled atomic orbitals.

The fundamental idea is that orbitals of atomic nature mix to create new atomic orbitals, which may contain the same amount of electrons as original orbitals in the atomic scale. The fusion of orbitals of atomic nature could result in completely different forms, energy levels, and more.

In the most basic case of hybridization, carbon atoms can utilize their three orbitals with p-type occupied singly.

Sp3 

Another kind of hybridization is sp3, where three p orbitals join to form a hybrid orbital. The hybrid orbitals are characterized by trigonal symmetry and form an angle of 120 degrees with one the other.

This can result in a tetrahedral arrangement of bonds, which we observed in methane and ethylene. This is also apparent in phosphorus pentachloride. This contains 5 Sp3 hybridized orbitals with equal energy and is distinguished by its trigonometric bipyramidal form.

The Hybrid Orbitals

The hybrid orbitals are aligned at an angle of 120 degrees toward each other and are on the horizontal plane. The two remaining orbitals are situated at 90-degree angles to the hybrid orbits of the equatorial and are located in the vertical plane.

The hybridized orbitals of sp3 have the same number of characters for s and p, like those of the original orbitals, while the sp2 hybridized orbitals are like SP orbitals. However, they don’t contain as many s or characters as the original ones.

Sp3 Hybridization

In the event of the sp3 hybridization process, we can expect every carbon atom to possess four carbon-hydrogen bonds, which will be a tetrahedral arrangement of bonds. The C-H-C and H-C-H angle of bonds is similar to 109.5 degrees, while the Acid (OH) group’s bond to carbon atoms will be at the angle of 109.5 degrees.

The sp3 hybridized atoms could be polar or non-polar dependent on the chemical interactions between the C-C and C-H bonds. The sp3 atoms will exhibit an increased bond-bond electrostatic attraction between the two C-C sigma bonds than between those two C-H bonds. This repulsion could cause the bond angles to widen and close from their 120deg ideal angles to reduce the resistance force.

Polar Or Non-polar?

The polarity of a molecule refers to the number of electric charges around it. The electronegativity of the atoms within the bonds determines this. Therefore, a molecule that distributes electrons equally between its atoms is considered non-polar, and a molecule with significant differences in electronegativity can be classified as not polar.

The primary distinction between polar and bonds that are not polar is the fact elements in polar bonds are attracted to the shared electrons differently. The molecule is therefore characterized by dipole energy which results in one end of the molecule possessing negative charges (d-) while the other has positive charges (d+).

A non-polar covalent bond will have the same proportion of electrons in the atoms. This is partly due to the atoms’ electronegativity levels, which indicates the degree to which they are attracted to the same pair of electrons.

Electronegativity

However, bonds with different electronegativity levels can be polar if the element with the highest electronegativity isn’t associated with any electronegative element. A molecule, for instance, composed of two chlorine atoms, C2H4, is a covalent, polar bond since the carbon atom draws more electrons away from the chlorine atom than the chlorine atom.

Another crucial aspect to consider when deciding if a molecule is polar molecular geometry. This refers to the molecule’s shape and the size and position of its molecules atoms. For example, carbon dioxide can be described as a linear molecule with two polar bonds. In contrast, water is a bent structure. An extremely high electronegativity. Oxygen atoms draw charges away from carbon atoms.

Because there is no underlying symmetry in the molecules, the individual dipoles of bonds cannot cancel each other out, and the total molecular polarity is zero. If a molecule is more complex, like the boron trifluoride (BF3), the trigonal configuration of the three bonds leads to the absence of a general dipole.

The Carbon-Oxygen Double Bond 

Found in formaldehyde (methanal) as well as the carbon-nitrogen triple bond of Acetonitrile (cyano methane) are covalent bonds that are both polar. This is because the elements that are more electronegative within these bonds take electrons from carbon atoms, making them less appealing compared to the elements with lower electronegative.

In addition, the polarity of molecules is usually affected by the interactions with their polar bond with other polar molecules. This is referred to as the dipole-dipole interplay. It is less effective than metallic, ionic, or covalent bonds. However, it is responsible for the general polarity of a molecule.

To understand the concept of a polar bond, it’s important to understand how it functions. When a polar bonds, one atom pulls on the electron pair shared by the other more strongly than another, resulting in dipole moments. This creates areas that are partially positive and negative charges, which can create interesting interactions between molecules.

FAQ’s

Describe CH3CH3.

Ethane, a colourless and odourless gas that is frequently used as fuel, has the chemical formula CH3CH3.

What is the CH3CH3 bond angle?

In CH3CH3, the bond angle is 109.5 degrees.

What is the CH3CH3’s molecular geometry?

Each carbon atom in CH3CH3 is coupled to four other atoms in a tetrahedral arrangement, giving the compound a tetrahedral molecular geometry.

What does CH3CH3 hybridization entail?

In CH3CH3, the carbon atoms are sp3 hybridised. It follows that each carbon atom has four orbitals, each of which can be used to create four covalent bonds with other atoms.

How polar or nonpolar is CH3CH3?

A non-polar molecule is CH3CH3. As the electrons in covalent bonds are equally distributed among the atoms due to the electronegativity of carbon and hydrogen, there is no net dipole moment.

What are some typical applications for CH3CH3?

The primary uses of ethane are as a fuel for cooking and heating as well as as a starting point for the synthesis of compounds like ethylene and polyethylene. Moreover, it serves as a propellant in aerosol sprays and a refrigerant.