Periodic Table Notes PDF

THE PERIODIC TABLE The periodic table consists of all known elements, their symbols, atomic number, and the mass number. Rows are called periods columns are called groups ARRANGEMENTS OF ELEMENT IN THE PERIODIC TABLE Elements are arranged in rows (periods) according to increasing atomic number The...

THE PERIODIC TABLE The periodic table consists of all known elements, their symbols, atomic number, and the mass number. Rows are called periods columns are called groups ARRANGEMENTS OF ELEMENT IN THE PERIODIC TABLE Elements are arranged in rows (periods) according to increasing atomic number The elements are represented by symbols, with mass numbers at the top and atomic numbers at the bottom e.g. 27Al13. Elements in the same period have the same number of shells e.g. all elements in the table above are in period 2 and have 2 shell. Elements in the same group have same number of electron in the outermost shell. (Download periodic table) Examples Group 1 Group 7 Group 8/0 (fully- filled) Li 2.1 F 2.7 He 2 Na 2.8.1 Cl 2.8.7 Ne 2.8 K 2.8.8.1 Br 2.8.8.7 Ar 2.8.8 Elements in the same group have similar chemical properties because they have same number of electrons In the outermost shell. Note: chemical reactions only involve transfer of electrons in the outermost shell. Examples: Lithium + oxygen---------- lithium oxide Li+O2 Li2 O Sodium + oxygen----- sodium oxide Na +O2------- Na2 O The elements are represented by symbols, with mass numbers at the top and atomic numbers at the bottom e.g. 27Al13. CHEMICAL FAMILIES Group one elements are called Alkali metals. Group 2 elements are called Alkaline earth metals. Group 7 elements are called Halogens. Group 8 or 0 elements are Noble gases. Elements that do not belong to a group (They lie between group2 and 3) are called Transition metals. Relation between electron configuration and the position of an element in the periodic table. The last number of the electron configuration gives the group of the element. The number of shells is same as the period number. The periodic table is divided into metals and non-metals Properties of metals 1. high melting and boiling points. 2. shiny when freshly cut. 3. malleable (can be hammered into shapes) 4. ductile, (can be pulled into wires) 5. good conductors of heat and electricity 6. form ionic compounds 7. form positive ions in their compounds. Properties of non-metals 1. Low melting and boiling points 2. Brittle when solids 3. Do not conduct electricity except graphite 4. Do not conduct heat except diamond 5. Form both ionic and covalent compounds 6. Form negative ions except Hydrogen Note 1. The only liquid metal is mercury, the rest are solids.2. The only liquid non-metal is bromine, the most are gases and a few solids. IONS An ion is a charged particle or atom. There are two types of ions: cations and anions Cations are positively charged ions e.g. Na+ , Mg+2 , NH4 + , Al+3 Anions are negatively charged ions e.g. Cl_ , O2_, N3_. Atoms of elements in group 0(noble gases) do not form ions because they have a fully filled outer most shell. Atoms of elements from all the other groups form ions so that they can have a fully filled outermost shell like noble gases. These atoms form ions by either loosing or gaining electrons. This electron transfer only happens during a chemical reaction. Cations Cations are positively charged ions. Cations are formed when atoms loose electrons. Group 1 lose 1 electron to form an ion with positive 1 e.g. Na+ Group2 lose 2 electrons to form an ion with positive 2 e.g. Mg+2 Group 3 lose 3 electrons to form an ion with positive 3 e.g. Al+3 Group 4 lose 4 electrons to form an ion with positive 4 e.g. Pb+4 Anions Anions are negatively charged ions. They are formed when atoms gain electrons. Atoms of elements from group 4,5,6 and 7 form anions. Group 4 gain 4 electron to form an ion with negative 4 e.g. C4- Group 5 gain 3 electron to form an ion with negative 3 e.g. N3-. Group 6 gain 2 electron to form an ion with negative 2 e.g. O2-. RADICAL A radical is a group of atoms that exist and react as one unit with one net charge. VALENCY Valency refers to the number of electrons lost or gained by an atom or radical. It is also called the combining power. If the atom or radical is charged, the charge gives the valency because it represents number of electrons lost or gained. To get valency of elements on the periodic table, check the Group. CHEMICAL FORMULA A chemical formula represents a compound or molecule using chemical symbols. We can work out the chemical formula using the following steps: 1.write the symbols of elements or radical present in the compound. 2.Put the valency of each at the top. 3.Exchange the valencies and write at the bottom 4. Write the chemical formula putting valency numbers at the bottom. NB For a radical, put bracket then the valency number below it. If the two valency numbers in the formula have common factor, simplify Chemical Equations A chemical equation shows chemical reaction using symbols and chemical formula. A chemical equation must be balanced to make sure the number of atoms of each element on the reactant side equals the number of atoms of each element on the product side. There are 3 types of equations that represent a chemical reaction. Word equation Chemical equation. (use symbols) Ionic equation When writing chemical equation, some elements must be written as molecules because they exist freely in nature as molecules. These are Oxygen O2 Hydrogen H 2 Nitrogen N 2 State Symbols The state symbols in brackets show the physical state of. the substance at the reaction temperature. Solid (s), liquid (l), gas (g), or dissolved in water (aq). aq is called aqueous which comes from the Latin word aqua meaning water. Chemical equations must have state symbols in brackets below each compound or element.