Chemistry Lecture 1 and 2: Chemistry Basics - Atomic Theory PDF

CHEMISTRY BASIC: THE ATOMIC THEORY CHE 101_LECTURE 1 AND 2 1 THE ATOMIC THEORY ATOM ▪ The smallest piece of an element that maintains the identity of that element ▪ Atom comes from a Greek word that means “indivisible” ▪ Atoms themselves are composed of smalle...

CHEMISTRY BASIC: THE ATOMIC THEORY CHE 101_LECTURE 1 AND 2 1 THE ATOMIC THEORY ATOM ▪ The smallest piece of an element that maintains the identity of that element ▪ Atom comes from a Greek word that means “indivisible” ▪ Atoms themselves are composed of smaller parts called subatomic particles Modern Atomic Theory ▪ All matter is composed of atoms. ▪ Atoms of the same element are the same; atoms of different elements are different. ▪ Atoms combine in whole-number ratios to form compounds. 2 THE ATOM Atomic Number: ▪ Number of protons in nucleus of an atom ▪ All atoms of the same element share same number of protons ▪ However, Atoms of the same element can have different numbers of neutrons ▪ Atoms of the same element with different numbers of neutrons are called Isotopes. 3 Isotopes Mass Number: ▪ The sum of the number of protons and neutrons in the nucleus is called the mass number. 4 Questions ▪ The most common carbon atoms have six protons and six neutrons in their nuclei. What are the atomic number and the mass number of these carbon atoms? ▪ An isotope of uranium has an atomic number of 92 and a mass number of 235. What are the number of protons and neutrons in the nucleus of this atom?. ▪ The number of protons in the nucleus of a tin atom is 50, while the number of neutrons in the nucleus is 68. What are the atomic number and the mass number of this isotope? 5 Atomic symbols ▪ It is also common to state the mass number after the name of an element to indicate a particular isotope. ▪ Carbon-12 represents an isotope of carbon with 6 protons and 6 neutrons ▪ Uranium-238 is an isotope of uranium that has 146 neutrons. 6 7 8 9 Atomic symbols 10 Questions ▪ What is the symbol for an isotope of uranium that has an atomic number of 92 and a mass number of 235? ▪ How many protons are in Na? ▪ Calculate the number of protons, neutrons, and electrons in an atom of aluminium. Write the symbol ▪ A neutral atom has an atomic number of 56 and a mass number of 138. Determine its name, symbol, number of protons, number of neutrons, and number of electrons. ▪ Using the periodic table, write the atomic number and symbol of the following elements 11 Questions ▪ Give complete symbols of each atom, including the atomic number and the mass number. ▪ an oxygen atom with 8 protons and 8 neutrons ▪ a potassium atom with 19 protons and 20 neutrons ▪ a lithium atom with 3 protons and 4 neutrons ▪ a magnesium atom with 12 protons and 12 neutrons ▪ a magnesium atom with 12 protons and 13 neutrons ▪ a xenon atom with 54 protons and 77 neutrons ▪ Americium-241 is an isotope used in smoke detectors. What is the complete symbol for this isotope? ▪ Carbon-14 is an isotope used to perform radioactive dating tests on previously living material. What is the complete symbol for this isotope? 12 Questions ▪ Give atomic symbols for each element. ▪ sodium ▪ argon ▪ nitrogen ▪ radon ▪ Give name for each element. ▪ Si ▪ Mn ▪ Fe ▪ Cr 13 Molecules and chemical nomenclature ▪ Define molecule. ▪ Name simple molecules based on their formulas. ▪ Determine a formula of a molecule based on its name. 14 Molecules and chemical nomenclature Molecules ▪ There are many substances that exist as two or more atoms connected together so strongly that they behave as a single particle. ▪ These multiatom combinations are called molecules. ▪ A molecule is the smallest part of a substance that has the physical and chemical properties of that substance. ▪ A molecule, is composed of more than one atom ▪ Eg Oxygen, Hydrogen, Nitrogen, Fluorine, Chlorine, Bromine, Iodine 15 Molecules and chemical nomenclature Molecular Formula ▪ A formal listing of what and how many atoms are in a molecule ▪ Hydrogen is H2, ▪ H is the symbol for hydrogen ▪ The subscript means, there are two atoms of this element in the molecule ▪ O2, N2 ▪ S8, P4 ▪ If there is no numerical subscript on the right side of an element’s symbol, it is assumed that there is only one atom in a formula 16 Molecules and chemical nomenclature Sulphur and Phosphorus ▪ The connection is called a chemical bond 17 Molecules and chemical nomenclature Rules of Chemical Nomenclature 1. Identify the elements in the molecule from its formula. This is why you need to know the names and symbols of the elements 2. Begin the name with the element name of the first element. If there is more than one atom of this element in the molecular formula, use a numerical prefix to indicate the number of atoms 5 penta Number of Atoms Prefix 6 hexa 1 mono 7 hepta 2 di 8 octa 3 tri 9 nona 4 tetra 10 deca 18 Molecules and chemical nomenclature Rules of Chemical Nomenclature 1. Identify the elements in the molecule from its formula. This is why you need to know the names and symbols of the elements 2. Begin the name with the element name of the first element. If there is more than one atom of this element in the molecular formula, use a numerical prefix to indicate the number of atoms 3. Name the second element by using three pieces: a. a numerical prefix indicating the number of atoms of the second element, plus b. the stem of the element name (e.g., ox for oxygen, chlor for chlorine, etc.), c. plus c. the suffix -ide. 19 4. Combine the two words, leaving a space between them. Molecules and chemical nomenclature Rules of Chemical Nomenclature 1. SO2 2. CO2 3. SO3 4. CO ▪ In some cases, when a prefix ends in a or o and the element name begins with o we drop the a or o on the prefix. ▪ monooxide = monoxide ▪ pentaoxide = pentoxide 20 Molecules and chemical nomenclature Rules of Chemical Nomenclature ▪ Nitrogen trichloride ▪ Diphosphorus pentoxide 21 Questions 1. Name each molecule. ▪ PF3 ▪ CO ▪ Se2Br2 ▪ SF4 ▪ P2S5 2. Give the formula for each molecule. ▪ carbon tetrachloride ▪ silicon dioxide ▪ trisilicon tetranitride ▪ disulfur difluoride ▪ iodine pentabromide 22