Briefly discuss the difference between isotopes, isobars and isotones and give two examples for each. Discuss briefly. Laws of Chemical Combination a The law of conservation of mass Lavoisior, — states that in chemical reaction, the mass of the system reactants and products remains constant. Hence matter is neither created nor destroyed in a chemical reaction. Silicon dioxide SiO2 , made up of elements silicon and oxygen, contains With what mass of oxygen will 10g of silicon combine?
In another experiment 16 g of mercury was obtained by the decomposition of Show that these data conform to the law of constant composition. In an experiment In another experiment Calculate the mass of O2 liberated in each experiment.
Show that the data explain the law of multiple proportions. Introduction In crystalline solids the atoms or ions are arranged in a periodic fashion and have long range order. By translating atoms or group of atoms in three dimensions, a crystal structure is formed. The crystal structure of a material is based on the crystal lattice, which is an imaginary point in space.
This array of points are not arbitrary but follows a set of rotational and translation rules. Unit cell — is the smallest group of lattice points that displays the full symmetry of the crystal structure. The unit cell has all the properties found in the bulk crystal. The possible geometry and CN of ionic solids can be predicted by radius ratio calculation.
Calculate the radius ratio and predict the CN and geometry. Activity 2. In a crystal structure, the centers of atoms, ions, or molecules lie on the lattice points. While cubes may easily be stacked to fill up all empty space, unfilled space will always exist in the packing of spheres. To maximize the efficiency of packing and minimize the volume of unfilled space, the spheres must be arranged as close as possible to each other.
They could be placed directly over spheres in the first layer A to give a sequence denoted ABA. The third layer is completely different than those first two layers and is stacked in the depressions of the second layer.
Thus, By: Bezabih Kelta M. For ionic compounds we can imagine the larger ions usually the anions forming the close-packed array, and cations occupying some of the holes. In either hexagonal hcp or cubic close-packed ccp or fcc arrays of B there is one octahedral and two tetrahedral holes per B atom. Zinc blende has cubic structure where as wurtzite is hexagonal.
Such structures are said to be polymorphs. Thus the difference between wurtzite and zinc blende lies in the different arrangements of layers of ions. Alpha molecules have low temperature while beta molecules have high temperature.
Outline the similarities and differences between cubic and hexagonal close-packed arrangements of spheres, paying particular attention to a coordination numbers, b interstitial holes and c unit cells.
State the coordination number of a sphere in each of the following arrangements: a ccp; b hcp; c bcc; d fcc; e simple cubic. Suggest, with reasons, which form is which. What name is given to this type of structural change?
Limitations to the Arrhenius Theory 1 The theory defined an acid or a base in terms hydrogen or hydroxyl compounds only. However, this does not explain the weak base ammonia NH3 , that does not contain OH- itself , which in the presence of water, releases hydroxide ions into solution. Note: A strong acid always has a weak conjugate base. A weak acid always has a strong conjugate base.
Activity 3. Write at least three acid-base conjugate pair reactions. It turns out that it may be more accurate to say that "Lewis acids" are substances which are electron-deficient or low electron density known as electrophiles and "Lewis bases" are substances which are electron-rich or high electron density - known as nucleophiles. The product of any Lewis acid-base reaction is called an adduct, a single species that contains a new covalent bond: By: Bezabih Kelta M.
Solvents which have no tendency to accept or release protons are known as aprotic solvents, e. Review Activity 3 1. Discuss briefly the advantages of Arrhenius definition of acids and bases. List at least 3 limitations of Arrhenius definition of acids and bases. If the pH of a solution is 9.
For each of the following pairs, give the stronger acid. Explain your answer. For the following reactions, label each species as an acid or a base. Indicate the species that are conjugates of one another.
Fig 4. It is the number of oscillations or waves per second. If one complete oscillation takes place in t seconds, the number of oscillations cycle in one second is. A radio operator broad casts at a frequency of What is the wavelength, in nanometers, of green light having a frequency of 6. The electromagnetic spectrum is largely invisible; we see only a tiny portion near the middle of the range.
This spectrum is continuous in that each color merges into the next without a break, like a rainbow. Instead of a rainbow colors, only a few colored lines are seen. Because of the appearance of the spectrum, it is often called discontinuous or line spectrum. The line spectrum is characteristic of a particular gas in the tube. These spectrum are the only radiations visible to human naked eye.
The spectrum consists of seven main colors. Table 4. Arrange these radiations in order of increasing wavelength. When sunlight is dispersed by passing through a prism a continuous spectrum is obtained. On the other hand, the dispersion of light from flame of vaporized compound is dispersed in a similar manner, only certain wavelengths of light are emitted.
These emitted lights are characteristic of that particular element. These produce line atomic spectra. Calcium, for instance produces a strong red color when put into a non luminous laboratory flame. This may serve as a qualitative test for the presence of the element. Since light is a form of energy these lines emitted by the atoms of an element are due to a loss of energy by the atoms. Specifically it is the electrons which gain energy and then give out this excess energy again in the form of radiation.
The loss of energy is in the form of a precise energy value quanta. The first person to notice a pattern in the lines of the visible region of the spectrum was John Balmer. Far IR Table 4. Calculate the wavelengths of the radiations by a hydrogen atom when an electron makes the following transitions. The wavelength of which of the above transitions is are in the visible region? The three postulates on which Bohr model was based are described: 1. In a hydrogen atom, the electrons revolve around the nucleus in certain definite circular paths called orbits, or shells.
The atom does not radiate energy while in one of its stationary states. That is even through it violates the idea of classical physics the atom does not change energy while the electrons moves with in an orbit.
Each shell or orbit corresponds to a definite energy. The electrons present in an atom can move from a lower energy level E lower to a level of higher energy Ehigher by absorbing the appropriate energy. Similarly, an electron can jump from a higher energy level Ehigher to a lower energy level Elower by losing the appropriate energy. The energy absorbed or lost is equal to the difference between the energies of the two energy levels, i.
The states with higher energies are called excited states. Thus the energy of a hydrogen atom in the ground state is - What is the wavelength of the emitted photon? Using figure 4. The only 'success' was with the hydrogen atom and similar atoms i.
Thus, it does not explain the properties of multi electronic atoms. It does not show conformity to the uncertainty principle, which states that it is not possible to know precisely both the energy and position of the electron at the same time. If the energy is known, the position cannot be determined with certainty.
He used the classical physics concepts to determine the electrons around the nucleus of an atom and considered an electron as macro objects. Activity The line spectra in H-atom has wavelength of Then determine n1. Quantum numbers are very significant because they can determine the electron configuration of an atom and a probable location of the atom's electrons.
They can also aid in graphing orbitals. The principal quantum number n - n can be any positive integer values 1,2,3…etc - The principal quantum number, n, designates or describes the principal electron shell the main energy levels. The first principal shell is also called the ground state, or lowest energy state.
It can also be a positive integer, but it cannot be larger than one less than the principal quantum number n-1 : i. It is called the magnetic quantum number because the effect of different orientations of orbitals was first observed in the presence of a magnetic field. This means that when ms is positive the electron has an upward spin, which can be referred to as "spin up. Example Boron atom has a total of five electrons. Write the four quantum numbers for each of the five electrons in the ground state.
This orbital can accommodate a total of two electrons. The remaining one electron is placed in the. What is the electron capacity of the third energy level? Assign the four quantum numbers for all electrons added to fluorine atom. Can the two electrons in the same orbital have the same spin quantum numbers? Explain in groups. Explain why each of the following sets of quantum numbers would not be possible for an electron, according to the rules for quantum numbers.
It is easy to lie down than stand up; bonding is natural way of allowing the elements to lie down. Chemical bonds form to lower the energy of the system, the components of the system becomes more stable through the formation of bonds. Octet rule - Octet rule - States that an atom tends to gain, lose or share electrons until there are eight electrons in its valence shell the nearest noble gas configuration at its row.
Note: - Hydrogen follows a special configuration called Duet rule 2 electrons in its outer most shell. What is chemical bonding? It is formed between metals and nonmetals. Example: Multiple covalent bonds are common for certain atoms depending upon their valence configuration.
For example, a double covalent bond, which occurs in ethylene C2H4 , results from the sharing of two sets of valence electrons. Atomic nitrogen N 2 is an example of a triple covalent bond. This results in a net negative charge within the bond favoring the more electronegative atom and a net positive charge for the least electronegative atom. However, these are soluble in non- polar solvents.
The procedure for doing this can be summarized in the following steps: i. Write the electron configuration of the combining atoms and determine the valence shell electrons of each atom. Add the valence shell electrons of all combining atoms charge on the molecule: if the molecule is positively charged, subtract the number of charges from the total valence electrons and if the molecule is negatively charged add the number of charge to the total valence shell electrons of the molecule.
Decide the central atom: In many instances the arrangements of atoms can be inferred from the formula, followed by the atoms that surround the central atom.
Once we know the arrangement of atoms in the molecule, we can go about distributing the valence electrons. The rules to decide the central atom a The atom with fewer numbers is taken as central atom. Share a pair of electron between central atom and surrounding atom form a temporary single bond.
Complete the octet starting from the surrounding atom By: Bezabih Kelta M. Put any electron that is not shared between central and surrounding atom as after the surrounding atoms complete their octet is put as lone pair on the central atom vii. If the central atom has less than an octet, you must form multiple bonds so that each atom has an octet. Example: What is the Lewis structure for CCl4? Solution: First we need the arrangement of atoms.
Made for sharing. Download files for later. Send to friends and colleagues. Modify, remix, and reuse just remember to cite OCW as the source. Lecture Handouts. Kimberly Berkowski 10 Alkenes Dr. Kimberly Berkowski 18 Alkyl Halides Dr. Sarah O'Connor 25 Aromaticity Prof. Sarah O'Connor 33 Carbonyl Chemistry cont. Sarah O'Connor 35 Multistep Synthesis cont.
Sarah O'Connor. Need help getting started? Don't show me this again Welcome! Thermodynamics, Kinetics, Reaction Coordinate Diagrams. Alkyl Halides, Nucleophilic Substitution Reactions cont. Alkyl Halides: Elimination Reactions, Aromaticity cont.
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