Chemical properties of oxides

Basic gas laws.Boyle's law (sometimes referred to as the Boyle–Mariotte law): at constant temperature the volume of a gas is inversely proportional to its pressure. T = const Inverse proportionality occurs when one variable gets larger by the same factor as another gets smaller. Charles’s Law: at constant volume the pressure of a gas is directly proportional to its temperature. V = const.Charles defi ned a new temperature scale in which the lowest possible temperature is 0^оС absolute, corresponding to -273.15 ^оС This temperature is called absolute zero. The symbol T is used for absolute temperature, and t is used for Celsius temperature: T = t + 273.15 Temperatures of approximately 0.000001 K have been produced in laboratories, but 0 K has never been reached. Gay-Lussac's Law: at constant pressure the volume of a gas is directly proportional to its temperature. P = const A temperature of 0^оC and a pressure of 1.00 atm (760 mm Hg, 101.3 kPa) constitute a set of conditions for a gas often called standard temperature and pressure (abbreviated STP). Combined gas law. The combined gas law is a gas law that combines Charles's law, Boyle's law, and Gay-Lussac's law. There is no official founder for this law; it is merely an amalgamation of the three previously discovered laws.The combined gas law clearly states that: the ratio between the pressure-volume product and the temperature of a system remains constant. This can be stated mathematically as where: P is the pressure; V is the volume; T is the temperature measured in Kelvin; k is a constant (with units of energy divided by temperature).For comparing the same substance under two different sets of conditions, the law can be written as:

MOLE. MOLAR MASS. In chemical processes involve the smallest particles - molecules, atoms, ions, electrons. The number of these particles even in small quantity of substances is very large. Therefore, to avoid mathematical operations with large numbers, to characterize the quantity of a substance involved in a chemical reaction, a special unit is used - the mole. Mole - is the amount of the substance, which contains a number of particles (molecules, atoms, ions), equal to the Avogadro's constant: N_A = 6.0221367·10²³ mol^-1 This number is about the number of grains of sand that would fi t into a sphere the size of the Earth! Remember the value of this number to at least three signifi cant digits. Avogadro’s constant (or Avogadro’s number) N_A is defined as the number of atoms contained in 12 g of carbon isotope ¹²C: Thus, one mole of substance contains 6.02 • 10²³ particles of this substance. Any amount of a substance can be expressed as a certain number of moles of ν (nu): where N – number of particles of the substance; N_A – Avogadro’s constant. The molar mass of the substance (M) – is the mass of 1 mole of the substance. The molar mass of any substance can be calculated, when mass (m) and amount of substance (ν) are known: Accordingly, knowing the mass and molar mass of the substance, it is possible to calculate the number of moles: or find the weight of substance from the number of moles and molar mass: m = ν • MThus, mole is a quantity of a substance containing the same number of particles, but having a different weight for the different substances, because substance particles (atoms and molecules) has different weight. For example: calculation the molar mass of nitric acid HNO₃.M_r (HNO₃) = A_r (H) + A_r (N) + 3·A_r (O) = 1 + 14 + 3·16 = 63 g/mol.

Atomic structure. Dalton’s atomic theory. Atomos, the Greek root of the word atom, means “indivisible.” It was originally believed that the atom was the ultimate indivisible particle of which all matter was composed. Lord Rutherford showed in 1911 that the atom is not homogeneous, but rather has a dense, positively charged center surrounded by electrons. Subsequently, scientists have learned that the nucleus of the atom can be subdivided into particles called neutrons and protons. In fact, in the past two decades it has become apparent that even the protons and neutrons are composed of smaller particles called quarks. For most purposes, the nucleus can be regarded as a collection of nucleons (neutrons and protons), and the internal structures of these particles can be ignored. The number of protons in a particular nucleus is called the atomic number (Z), and the sum of the neutrons and protons is the mass number (A). Atoms that have identical atomic numbers but different mass number values are called isotopes. In 1803, John Dalton (1766–1844) proposed his atomic theory, including the following postulates. 1. Matter is made up of very tiny, indivisible particles called atoms.2. The atoms of each element has mass, but the mass of the atoms of one element is different from the mass of the atoms of every other element. 3. Atoms combine to form molecules. When they do so, they combine in small, whole-number ratios 4. Atoms of some pairs of elements can combine with each other in different small, whole-number ratios to form different compounds.5. If atoms of two elements can combine to form more than one compound, the most stable compound has the atoms in a 1: 1 ratio. (This postulate was quickly shown to be incorrect.) The postulates of Dalton’s atomic theory explained the laws of chemical combination very readily. 1. The law of conservation of mass is explained as follows: Because atoms only exchange “partners” during a chemical reaction and are not created or destroyed, their mass is also neither created nor destroyed. This, mass is conserved during a chemical reaction. 2. The law of defi nite proportions is explained as follows: Because atoms react in definite integral ratios (postulate 3), and atoms of each element have a definite mass (postulate 2), the mass ratio of one element to the other(s) must also be definite. 3. The law of multiple proportions is explained as follows: Because atoms combine in different ratios of small whole numbers (postulate 4), for a given number of atoms of one element, the number of atoms of the other element is in a small, whole-number ratio. A given number of atoms of the fi rst element implies a given mass of that element, and a small, whole-number ratio for the atoms of the second element (each of the same mass) implies a small, whole-number ratio of masses of the second element.

The Periodic system and Periodic law. The classic Periodic Law formulation of D.I.Mendeleev is as states: the properties of elements and therefore the properties of the simple and complex substances they form are in the periodic dependence on their atomic weight. Nowadays the formulation is: the properties of elements and therefore the properties of the simple and complex substances they form are in the periodic dependence on the charge of the atomic nuclei. letters in the boxes are the symbols for the elements; these abbreviations are based on the current element names or the original names. The number shown above each symbol is the atomic number (number of protons) for that element. For example, carbon (C) has atomic number 6, and lead (Pb) has atomic number 82. Most of the elements are metals. Metals have characteristic physical properties such as effi cient conduction of heat and electricity, malleability (they can be hammered into thin sheets), ductility (they can be pulled into wires), and (often) a lustrous appearance. Chemically, metals tend to lose electrons to form positive ions. For example, copper is a typical metal. An element block is a set of elements located in adjacent element groups. Element blocks are named for their characteristic orbital, which is determined by the highest energy electrons: s-block First two groups of the periodic table -- alkali metals and alkaline earths p-block Last six element groups of the periodic table, excluding helium. The p-block elements include all of the nonmetals except for hydrogen and helium, the semimetals, and the post-transition metals. d-block Transition metals of element groups 3-12. f-block Inner transition elements, usually the lanthanide and actinide series, including lanthanum and actinium. g-block (proposed) Would be expected to include element with atomic numbers higher than 118.

Periodic Trends in Atomic Properties. Periodic trends are specific patterns that are present in the periodic table, which illustrate different aspects of a certain element, including its size and its properties with electrons. The main periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, melting point, and metallic character. The periodic trends that arise from the arrangement of the periodic table provide chemists with an invaluable tool to quickly predict an element's properties. These trends exist because of the similar atomic structure of the elements within their respective group families or period and the periodic nature of the elements. Electronegativity Trends Electronegativity measures an atom's strength to attract and form bonds with electrons. This property exists due to the electronic configuration of atoms. 1. As you move to the right across a period of elements, electronegativity increases.; 2.As you move down a group, electronegativity decreases.; 3.Important exceptions of the above rules include the noble gases, lanthanides, and actinides.; 4.As for the transition metals, while they have values, there is little variance among them as you move across the period and up and down a group. Ionization Energy Trends Ionization Energy is the amount of energy required to remove an electron from a neutral atom in its gaseous phase. Thus, ionization energy increases from left to right on the periodic table. 1. The ionization energy of the elements within a period generally increases from left to right. This is due to valence shell stability. 2. The ionization energy of the elements within a group generally decreases from top to bottom. This is due to electron shielding. 3. The noble gases possess very high ionization energies because of their full valence shell. Note that Helium has the highest ionization energy of all the elements. Electron Affinity Trends Like the name suggests, electron affinity describes the ability of an atom to accept an electron. This causes the electron to move closer to the nucleus, thus increasing the electron affinity from left to right across a period. 1. Electron affinity increases from left to right within a period. This is caused by the decrease in atomic radius. 2. Electron affinity decreases from top to bottom within a group. This is caused by the increase in atomic radius.

Chemical bond. Mechanisms of formation. Basic characteristics of the chemical bond. A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. Basic characteristics of the chemical bond are: bond energy, bond length and bond angle. The bond energy is a measure of the amount of energy needed to break apart one mole of covalently bonded gases. The SI units used to describe bond energy is kilojoules per mole of bonds (kJ/mol). Bond length is the distance between the centers of two covalently bonded atoms. The length of the bond is determined by the number of bonded electrons (the bond order). Generally, the length of the bond between two atoms is approximately the sum of the covalent radii of the two atoms, X + Y.Bond length is given in picometers. Therefore, the bond length of a triple bond < double bond < single bond. Bond angle is the angle that is formed between two adjacent bonds on the same atom. Covalent Bonding. Metal atoms can donate electrons to nonmetal atoms, but nonmetal atoms do not form monatomic positive ions because they would have to donate too many valence electrons to form octets. (Single nonmetal atoms do not donate electrons at all, but some groups of nonmetal atoms can. This will be discussed later in this section. Nonmetal atoms can accept electrons from metal atoms if such atoms are present; otherwise, they can attain an octet by electron sharing. A covalent bond consists of shared electrons. One pair of electrons shared between two atoms constitutes a single covalent bond, generally referred to as a single bond. An unshared pair of valence electrons is called a lone pair. Elements or compounds bonded only by covalent bonds form molecules. Donor-Acceptor Bond (DAB) – special type of covalent bond DAB (also coordination bond), a term denoting one of the ways in which a chemical covalent bond is formed. The ordinary covalent bond between two atoms is due to the interaction of two electrons, one from each atom. The donor-acceptor bond is formed by a pair of electrons from one atom (the donor) and a free (unfilled) orbital from another (the acceptor). Hydrogen bonding is the intermolecular force of attraction between a hydrogen atom in one molecule and a small, highly electronegative atom with an unshared pair of electrons in another molecule. Metallic bonding Metallic bonding is the electromagnetic interaction between delocalized electrons, called conduction electrons, gathered in an " electron sea", and the metallic nuclei within metals. Understood as the sharing of " free" electrons among a lattice of positively charged ions (cations), metallic bonding is sometimes compared with that of molten salts; however, this simplistic view holds true for very few metals.

Oxydation-reduction reactions (redox-reactions). Reactions, in which one or more electrons are transferred, are called oxidation–reduction reactions or redox reactions.We defi ne the oxidation states (or oxidation numbers) of the atoms in a covalent compound as the imaginary charges the atoms would have if the shared electrons were divided equally between identical atoms bonded to each other or, for different atoms, were all assigned to the atom in each bond that has the greater attraction for electrons.Oxidation–reduction reactions are characterized by a transfer of electrons. In some cases, the transfer occurs in a literal sense to form ions.

Types of chemical reactions. 1. Decomposition Reactions – реакции разложения A compound breaks into parts. compound → element + element 2H₂O → 2H₂ + O₂

2. Synthesis Reactions – реакции присоединения (синтеза) Elements are joined together.
element + element → compound 2H₂ + O₂ → 2H₂O Compounds are joined together compound + compound → compound 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ 3. Single Displacement Reactions – реакции единичного замещения A single element replaces an element in a compound. element + compound → element + compound Zn + 2HCl → H₂ + ZnCl₂ 4. Double Displacement Reactions – реакции двойного замещения An element from each of two compounds switch places. compound + compound → compound + compound H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O 5. Combustion Reactions – реакции горения A hydrocarbon (a compound containing only carbon and hydrogen) combines with oxygen. The products of combustion are always carbon dioxide and water. hydrocarbon + oxygen → carbon dioxide + water CH₄ + 2O₂ → CO₂ + 2H₂O When metallic substances combine with oxygen, the result is an oxidation-reduction reaction. The rusting of iron - 4Fe + 3O₂ → 2Fe₂O₃Chemical reactions can be classified in other ways as well: Neutralization Reactions – реакция нейтрализации - Special types of double displacement reactions that involve the reaction between an acid and base to form a salt and water.acid + base → salt + water A suspension of solid magnesium hydroxide in water is widely used as an antacid to neutralize excess stomach acid: Mg(OH)₂ (s) + 2HCl (aq) → MgCl₂ (aq) + 2H₂O Oxidation-Reduction Reactions – окислительно-восстановительные реакции Any reaction in which elements experience a change in oxidation number. one atom gains e^-minus and another atom looses e^-minus S + O₂ → SO₂ In the reaction above, sulfur and oxygen both have an oxidation number of zero before the reaction. After the reaction, sulfur is +4 and oxygen is − 2. Precipitation Reactions – реакции осаждения. Aqueous reactions that involve the formation of a precipitate (solid). soluble compound + soluble compound → insoluble compound 2KI (aq) + Pb(NO₃)₂ (aq) → 2KNO₃ (aq) + PbI₂ (s) ↓ The physical state symbol (aq) says the reaction is taking place in a water solution. The physical state symbol (s) says the lead (II) iodide is a solid - therefore insoluble in the solution. Hydrolysis (гидролиз) is a reaction involving the breaking of a bond in a molecule using water.

Solutions. Concentration units. Solution - a mixture consisting of a solute and a solvent. Solute - component of a solution present in the lesser amount. Solvent - component of a solution present in the greater amount. Concentration - amount of a solute present in a solution per standard amount of solvent There are numerous ways of expressing concentrations. It will be important to know the units used to express each concentration, as these units essentially define the concentration. Percent by Mass (Weight percent, ω %) The percent by mass of a solute is simply the number of grams of solute in exactly 100 g of solution. It can be calculated as exactly 100% times the mass of the solute divided by the mass of the entire solution. Molality (m) Molality is often used as the concentration unit involved in calculations dealing with colligative properties, such as freezing point depression, boiling point elevation and osmotic pressure. Molarity (M) Chemical reactions often take place when two solutions are mixed. To perform stoichiometric calculations in such cases, we must know two things: (1) the nature of the reaction, which depends on the exact forms the chemicals take when dissolved, and (2) the amounts of chemicals present in the solutions, usually expressed as concentrations. The concentration of a solution can be described in many different ways. At this point we will consider only the most commonly used expression of concentration, molarity (M), which is defi ned as moles of solute per volume of solution in liters: Normality (molar concentration of equivalent, N, C_eq) Another concentration measure sometimes encountered is normality (symbolized by N). Normality is defi ned as the number of equivalents per liter of solution, where the defi nition of an equivalent depends on the reaction taking place in the solution