Atoms and Molecules - Model of Matter PDF

MODEL OF MATTER – ATOMS AND MOLECULES Chapter 8  8.1 What is the Simplest Unit of an Element and How Do We Represent Its Structure?  Pg 66 What is an atom? An atom is the simplest unit of an element. In Chapter 3, you...

MODEL OF MATTER – ATOMS AND MOLECULES Chapter 8  8.1 What is the Simplest Unit of an Element and How Do We Represent Its Structure?  Pg 66 What is an atom? An atom is the simplest unit of an element. In Chapter 3, you learnt about the Periodic Table of Elements. Each element in the Periodic Table consists of only 1 type of atom. The element carbon is only made up of carbon atoms, while the element oxygen is only made up of oxygen atoms.  Pg 69 STRUCTURE OF AN ATOM An atom contains three types of sub-atomic particles. ✔ proton, in the nucleus of the atom ✔ neutron, in the nucleus of the atom ✔ electron, moves around the nucleus  Pg 70 CHARGE OF AN ATOM The 3 sub-atomic particles have different relative charges and relative masses. type of sub- position in the relative charge relative mass atomic particle atom within the proton +1 1 nucleus within the neutron 0 1 nucleus around the electron –1 nucleus  Pg 70 CHARGE AND MASS OF AN ATOM Why do we use “relative charge” and “relative mass” instead of “charge” and “mass”? Since atoms are so small, the actual charge and mass of the sub-atomic particles are very small too. Therefore, we take the ratio of the charges (and masses) of the proton, neutron and electron. RATIO OF CHARGE RATIO OF MASS proton : neutron : electron proton : neutron : electron  Pg 71 CHARGE AND MASS OF AN ATOM The following table shows the number of protons, neutrons and electrons in 3 elements, and the overall charge. What do you observe about the data? number of Since the protons number of number of number of overall positive and and type of atom protons electrons neutron charge negative electrons charges are are always balanced, the same. carbon 6 6 6, 7 or 8 0 and neutrons do How does not have a this affect nitrogen 7 7 7 or 8 0 charge, the the overall overall charge? charge of uranium 92 92 143 or 146 0 an ATOM is 0.  Pg 71 CHARGE AND MASS OF AN ATOM The following table shows the number of protons, neutrons and electrons in 3 elements, and the overall charge. What do you observe about the data? Number of number of number of number of overall neutrons is type of atom protons electrons neutron charge not equal to the number of protons. carbon 6 6 6, 7 or 8 0 Some types of atoms nitrogen 7 7 7 or 8 0 have different number of uranium 92 92 143 or 146 0 neutrons.  Pg 71 CHARGE AND MASS OF AN ATOM RATIO OF MASS Recall this proton : neutron : electron Since the electrons are much lighter than the protons and neutrons, the mass of an atom is mainly contributed by the mass of the nucleus, or the mass of protons and neutrons in the nucleus.  8.2 How can the Number of Protons in an Atom be Used to Identify an Element?  Pg 72 IDENTIFYING AN ELEMENT From the Periodic Table proton number proton number – number of protons in an atom mass number mass number - total number of protons (nucleon number) and neutrons in an atom How many protons and neutrons does an atom of lithium have? Lithium has 3 protons and 4 neutrons.  Pg 72 IDENTIFYING AN ELEMENT Based on the Periodic Table, what is unique about each element?  Pg 72 IDENTIFYING AN ELEMENT Each element has a different proton number. Elements are arranged in ascending proton number. number of number of number of type of atom protons electrons neutron hydrogen 1 1 0 helium 2 2 2 lithium 3 3 4 As a result of having different proton numbers, different elements have different physical and chemical properties.  8.3 How Do We Represent the Simplest Units of Elements and Some Compounds?  Pg 75 REPRESENTATIONS OF ATOMS AND MOLECULES A molecule is made up of two or more atoms that are chemically combined. hydrogen atom hydrogen molecule water molecule To represent an atom of Atoms of the same Atoms of different an element, a single circle element can combine to elements can also labelled with the form a molecule. combine to form a chemical symbol of the molecule. element is used. H H H O H H  Pg 76 CHEMICAL FORMULA The chemical formula identifies each constituent element in a molecule by: its chemical symbol, and Indicates the number of atoms of the element. number of type of atom in type of molecule chemical formula atom(s) in the the molecule molecule hydrogen H2 hydrogen 2 hydrogen 2 water H2O oxygen 1  Pg 76 CHEMICAL FORMULA Recall from Chapter 3 Elements cannot be broken down into simpler substances. Compounds consist of two or more elements that are chemically combined together. molecule of an molecule of a element compound consists of only one type consists of two or more of atoms that are types of atoms that are chemically combined chemically combined N N O O O N O nitrogen molecule oxygen molecule nitrogen dioxide molecule  Pg 76 CHEMICAL FORMULA Classify the following substances as elements or compounds, based on the given chemical formula. Ammonia, NH3 Chlorine, Cl2 Carbon monoxide, CO  8.4 What are Some Applications of Atomic Technologies and the Possible Issues That can Arise from Them?  Pg 79 Applications of Atomic Technologies gold-plated orchid scans of parts of the human body using flowers medical imaging Does application of atomic technologies bring about ONLY benefits to mankind?  Pg 79 Possible Issues of Atomic Technologies What if human abuse our knowledge of atomic technologies, or accidents happen to beneficial explosion from atomic Fukushima nuclear disaster applications? bombs