Periodic Trends Chapter 6 Lesson 3 PDF

Chapter 6 Lesson 3 The periodic law : Atoms are arranged by increasing atomic number. The elements display a repeating pattern of chemical and physical properties. Periodic Trends : Periodic trends are patterns that are present in the periodic table. They show different properties of elements , an...

Chapter 6 Lesson 3 The periodic law : Atoms are arranged by increasing atomic number. The elements display a repeating pattern of chemical and physical properties. Periodic Trends : Periodic trends are patterns that are present in the periodic table. They show different properties of elements , and how these characteristics increase or decrease as you move across a row or down a column of the periodic table. Four main periodic trends : 1- Atomic Radius 2- Ionization Energy 3- Electronegativity 4- Ionic radius What is the trend for atomic radius as we go down a group? Vertical trend : As we go down a family , valence electrons are found in energy levels further from the nucleus. - As we go down a column the atomic radius will increase Quick practice Which one has a larger atomic radius ? O or S Ca or Be What is the horizontal trend for atomic radius? ( Trend across a period) As we move across a row ,we are still in the same energy level however the atomic number is increasing causing an increase in the effective nuclear charge.so the nucleus is stronger and it can attract more the outer most energy level causing a decrease in the atomic radius. Quick Practice Which atom is smaller? Mg or Si Ga or As 2- Ionization Energy What is ionization energy? Ionization energy is the energy required to remove an electron from an atom. It is measured in kilojoules KJ Ionization energy and atomic radius are inversely proportional. The larger the atom is the easier its electrons are removed. The amount of energy required to remove an electron depends on shielding. Shielding is when the core (inner) electrons block the protons from pulling on the valence electrons Ionization energy across column: As we go down a group the atomic radius increases so the amount of ionization energy needed to remove the electrons decreases. Ionization energy across a period As we go across a row , the atomic radius becomes smaller which means that the ionization energy will increase. -  The second ionization energy I.E is the energy required to remove the second electron(s). Always greater that first I.E. The third I.E is the energy required to remove a third electron, which is greater than 1st and 2nd I.E. Successive values of Ionization Energy: If you examine the previous table , you will notice that successive ionization energy for a certain element increases. From the previous table you will notice that the ionization energy at which the large increase in energy occurs is related to the number of valence electrons. For example magnesium has two valence electrons because the dramatic increase in ionization energy occurs after the second I.E value. 1. Element X has two valence electrons because between second and third ionization energy there is a dramatic increase in the IE. 2. Element Y has 4 valence electrons because after the third IE there is a dramatic increase in the IE values. 3. Element Z has three IE because after the third IE there is a dramatic increase in the IE values. 3- Electronegativity : What is electronegativity ? Electronegativity of an element indicates the relative ability of its atoms to attract electrons in a chemical bond. Electronegativity down a group : As we move down a group the electronegativity decreases. The electronegativity down a group decreases because the atomic radius increases so the ability of an atom to gain electrons decreases. Electronegativity across period : As we move from left to right in the periodic table , the electronegativity increases. Unit for electronegativity Melting and boiling point : Melting point : The melting point is the amount of energy needed to break a bond in order to change a substance from a solid state to a liquid state. Boiling point : The boiling point is the amount of energy required to break a bond to change a substance from a liquid state to the gas state. The size of the radius of the ion depends on the overall charge of the ion positive or negative 1- anions are larger than their respective atoms. Electron-electron repulsion forces them to spread apart Electrons outnumber protons The protons cannot pull the extra electrons more tightly toward the nucleus. 2- cations are smaller than their respective atoms Less electron-electron repulsion allows for them to come closer together Protons outnumber electrons The protons can pull the fewer electrons toward the nucleus more tightly If am electron that is lost is the only valence electron causing the electron configuration of the cation to be like a noble gas than the entire energy level is lost in this case the radius of the cation is much smaller than its respective atom.