Table of Contents Chapter: The Periodic Table Section 1: Introduction to the Periodic Table
What does periodic mean? Periodic means with a repeating pattern A periodic event is predictable
Periodic Table **Periodic Table is a table that shows all the chemical elements that have been discovered. **The elements in the P.T. are arranged according to their properties, in a repeating pattern. **This means that their properties can be predicted, according to their position in the P.T.
https://www.youtube.com/watch?v=fpnw BITSmgU The genius of Mendeleev's periodic table https://www.youtube.com/watch?v=oylt OhzpJL4 Mendeleev and The Modern Periodic Table
Mendeleev Russian chemist that publish a version of a P.T. in which the elements were arranged according to their atomic mass. He observed that this arrangement revealed a pattern.
Importance of Mendeleev s work: The importance of Mendeleev s work lies on the periodic table repeating patterns that he observed and described. By analyzing the properties of different elements already present in the PT, he could infer the properties of elements that were not discovered yet. With time, these missing elements were discovered and placed in the PT empty spots.
The repeating patterns allow scientists to: 1)make predictions about an element s chemical and physical properties, based on this element s position on the periodic table. (Elements with similar properties are placed in the same area of the periodic table) 1)Find the correct location of a new element in the periodic table.
Atomic Mass X Atomic Number Henry Moseley an English physicist realized that Mendeleev's table could be improved by arranging the elements according to atomic number ( number of protons in the nucleus of an atom) rather than atomic mass That how the Periodic Table is organized today
The organization of the PT - Textbook page 436 A period is a row of elements in the periodic table whose properties change gradually and predictably. Why???? Because the atomic number increases by one, when you move from one element to another. There are seven periods
The groups or families are the columns. A group contains elements that have similar physical or chemical properties. The periodic table has 18 columns of elements and each one is called a group or family.
Today s Periodic table : textbook page 435 Zones on the Periodic table PT is divided in different zones: Representative Elements Gr 1,2, 13 through 18 Transition Elements Gr 3 through 12 Inner Transition Elements Two rows placed below
Each element has an element key
The Element Keys Name of the element, symbol, atomic number, atomic mass, the state of matter (at room temperature), if they are synthetic or not. the color of the box will tell you the type of element ( metals, metalloids and nonmetals)
Metals nonmetals and Metalloids in the PT read page 438
Atoms X Elements Atoms are the building blocks of matter Atoms form elements (elements have one type of atom only) ***Atoms have chemical and physical properties that will be kept by the elements
Properties of Atoms and the pattern or trends in the periodic table The chemical and physical properties of atoms change according to the location of the atom in the periodic table Some of the properties are: ionization energy, electronegativity, reactivity, atomic radius, melting and boiling point
Atomic radius distance from the center of the nucleus to the last energy level of the electron cloud Atomic radius = the size of the atom
Graphs will reflect the PT trend- GROUP 1 atomic number increases and the radius increases
Properties of Atoms: Atomic Radius The atomic radius = the size of the atom. Atoms generally get smaller as you go across the periods
Graphs reflect the PT trend - PERIOD 4 Atomic Number increases but radius decreases
How can we explain that the radius of the atoms decreases, when the atomic number increases? We would imagine that the more electrons an atom has, the bigger the radius would be.
Explanation: open book page 467 Models of atoms Look at Group 1: Atomic Number increases and radius increases number of electrons increases but the electrons are not as packet there is more space that the atoms can occupy without being packet. (more energy levels to fit the electrons) The circles represent energy levels - the area where you find electrons
Explanation: open book page 467 Models of atoms Period: Atomic number increases and radius decreases - number of electrons increases with the atomic number, but the space available for the electrons is the same ( 2 energy levels)
Ionization Energy An ion is an atom that lost or received an electron. Ionization energy is also a property of the atoms and shows a pattern in the P.T.
Properties of Atoms: Ionization Energy Ionization energy is the energy required to remove an electron from an atom in the gas state of matter, to form a positive ion The higher the ionization energy, the more difficult it is to remove an electron, because the atom is very stable.
Ionization Energy - Group 1
Ionization Energy- Period 4
Usually metals have high melting and boiling points because the atoms are united by strong bonds.
Reactivity It is another property and it is the capacity of an atom, to react with another atom. Fluorine is the most reactive non-metal Francium is the most reactive of the metals Helium is the least reactive element You can notice a pattern of reactivity in the PT
Reactivity of Elements
Reactivity Why does the reactivity go UP when you move down in Groups 1 and 2 (metals) of the PT?
Reactivity of Group 1- alkali metals Electrons are found in the energy levels of the atoms. Lithium has 2 energy levels, Sodium 3 and Potassium 4.
Reactivity of Group 1- alkali metals Going down the group the reactivity increases because: -The atoms are bigger and there are more energy levels - the electrons in the outer energy level are less attracted by the positive nucleus and will react easily when compared to the ones closer to the nucleus
Reactivity and Electronegativity The elements that are very reactive, also have a high electronegativity. What is electronegativity?
IMPORTANT When atoms combine forming molecules, they can share, donate or receive electrons, forming chemical bonds.
Electronegativity is another property It is the tendency of an atom to attract the electrons of a bond when this atom is in a molecule. Ex: The chlorine atom has a higher electronegativity than the hydrogen atom, so the bonding electrons will be closer to the Cl than to the H in the molecule.
From left to right: atoms in a period have more protons, so the + charge in the nucleus is stronger, attracting more the electrons that will tend to stay closer to the nucleus.