Chapter 3: The Periodic Table and Atomic Properties PDF

1 Chapter 3 The Periodic Table and Some Atomic Properties Edited by Dr. Nazar Abdulaziz Elnasri -Dr. Wed Mohammed Chemistry department –BMC Asser ...

1 Chapter 3 The Periodic Table and Some Atomic Properties Edited by Dr. Nazar Abdulaziz Elnasri -Dr. Wed Mohammed Chemistry department –BMC Asser  2 Periodic table of elements and properties of atoms The arrangement of elements is in order of increasing atomic number (Z)  3 Periodic table of elements and properties of atoms The vertical columns of the table (numbered from 1 to 18 ) are called groups or families. Element in the same group have similar but not identical characteristics. The horizontal rows of the table (numbered from 1 to 7) are called periods. Each period contains elements with electrons in the same outer shell. Loading…  4 Classification of the Elements in Periodic Table Elements in the periodic table can be classified according to their natures, electronic configurations, and properties, as follows: Metals constitute the largest class of elements of the periodic table, and all of them are solids, except mercury (Hg) is a liquid at room temperature.  5 3.2. Classification of the Elements in Periodic Table Loading…  6 3.2. Classification of the Elements in Periodic Table  7 Characteristic properties of transition elements 1. High electrical and thermal conductivity 2. High melting point 3. Malleable – can be hammered into sheets 4. High tensile strength – can hold large loads without breaking 5. Ductile – can be drawn into wires  8 Atomic size or Radius (Atomic properties) The atomic size (or radius) is the half distance of closest approach between two identical atoms. When we move from the left to the right along a period, in the periodic table, the atomic size decreases. Conversely, it increases when we move from the right to the left. since there is an increase in core charge (Zeff increases), the outer shell electrons are attracted closer to the nucleus (it’s the same shell but there are more electrons in the shell as you move across the period). When we move from the top to the bottom along a group in the periodic table, the atomic size increases. Conversely, it decreases when we move from the bottom to the top. since there is an increase in the number of shells.  9 Atomic size or Radius (Atomic properties) Cation is smaller than atom from which it is formed. Excess of protons in the ion draws the outer electrons closest to nucleus. Anion is larger than atom from which it is formed. More repulsion between electrons and the ionic radius increases.  10 Ionization energy The ionization energy is the amount of energy it takes to detach one electron from a gas neutral atom If it is easy to detach an electron, it has low ionisation energy. If it is hard to detach an electron, it has a high ionisation energy The larger the atom the easier it is to detach an electron. The smaller the atom the harder to detach an electron  11 Ionization energy When we move from the left to the right along a period, in the periodic table, the ionization energy increases. Conversely, it decreases when we move from the right to the left. since there is an increase in core charge, the attraction is greater between the outer shell electrons and the nucleus. Therefore, electrons are harder to remove. Loading… When we move from the top to the bottom along a group in the periodic table, the ionization energy decreases. Conversely, it increases when we move from the bottom to the top. since there is an increase in the number of shells so the size of the atom is increasing, the attraction is weaker between the outer shell electrons and the nucleus. Therefore, electrons are easier to remove.  12 Electronegativity Electronegativity is the ability of an atom to attract a pair of electrons towards itself in a chemical bond. Same electronegativity A:A B is more electronegative than A A :B  13 Electronegativity When we move from the left to the right along a period, in the periodic table, the electronegativity increases. Conversely, it decreases when we move from the right to the left. since there is an increase in core charge, there is a greater attraction of the outer shell electrons to the nucleus. When we move from the top to the bottom along a group in the periodic table, the electronegativity decreases. Conversely, it increases when we move from the bottom to the top. since the electrons are further from the nucleus, there is a weaker attraction Electronegativit y  14 Endothermic and Exothermic energy 4-Electron Affinity  15 Addition reading 16 Addition reading Factors Affecting ionization energy