ATOMS • Starter: I have in front of me a beaker of water that has had sand mixed in and salt dissolved in. Using the techniques we learnt last lesson write a step by step guide to separating out the salt and sand. • Homework: Complete sheets on atomic structure of the first 20 elements. ATOMS • All atoms (except Hydrogen) are made from three types of particles. They are: • Protons – Positively charged particle • Neutrons – A neutral (no charge) particle • Electrons – Negatively charged particle STRUCTURE OF THE ATOM • Protons and neutrons are located in the nucleus • The electrons are located in the shells/orbits. Charge Mass Location Proton +1 Neutron neutral Electron -1 1 1 0 Nucleus Nucleus Shells MASS AND ATOMIC NUMBERS • Mass number – Total number of protons and neutrons in the nucleus. • Atomic number – Number of protons or electrons in the atom. • Number of neutrons = • Mass number – Atomic number • How many protons, electrons and neutrons does Lithium have? Example 9 Be has 4 …protons, …electrons and …-…=… neutrons Protons = atomic number Electrons = atomic number Neutrons = mass – atomic number 7 3Li has …protons, …electrons and …-…=… neutrons 19 9F has …protons, …electrons and …-…=… neutrons 27 13Al has …protons, …electrons and …-…=… neutrons What is the mass of an atom with ? 10protons, 10 neutrons and 10 electrons? ? 8protons, 8 neutrons and 8 electrons? ? 9protons, 10 neutrons and 9 electrons? ? 18protons, 22 neutrons and 18 electrons? • What can you tell me about the structure of aluminium's atoms from how it’s represented on the periodic table? • Using the periodic table in your books write down the element with the atomic number 15 • An atom from element “E” is represented as follows. What information can you give me about element E? Use your periodic tables! Isotopes • Lo1: To understand the terms Isotope and relative atomic mass • Lo2: To learn how to draw the electronic structure of elements STARTER • A) How many protons, neutrons and electrons does this element have? • B) Use your to find out atomic mass with atomic periodic table the name and of the element number 92 • C) Identify the element I have drawn on the board 197.0 79 SO IF ATOMIC MASS IS THE NUMBER OF PROTONS+ NEUTRONS What’s going on with Chlorine? 17 Protons 18 Neutrons 17 Electrons 17 Protons 20 Neutrons 17 Electrons CHLORINE CAN EXIST IN TWO FORMS Isotope: Atoms of an element with different numbers of neutrons. Isotopes have the same atomic number but different atomic mass numbers. Isotopes of an element have identical chemical properties (They behave the same way) Carbon has two isotopes C 12 and 14 C6 6 What is the difference? RELATIVE ATOMIC MASS • We measure the weight of elements in Atomic mass units (amu). The scale of atomic mass units is so that hydrogen, the lightest element has an amu of 1. • “The Relative Atomic Mass (Ar) of an element is the mass of an "average atom” taking into account different isotopes of the element and their relative abundance.” CALCULATING AR • We take the masses of the isotopes and multiply them by their relative Abundance before adding them together (Mass 1 x Abundance 1)+ (Mass 2 x Abundance 2)= Ar • Using Chlorine as an example because we know it has two isotopes; 35 and 37 with abundances of 75% and 25% respectively… 17 Protons 18 Neutrons 17 Electrons 17 Protons 20 Neutrons 17 Electrons CHLORINE CAN EXIST IN TWO FORMS Using the equation you just wrote in your books, calculate the Ar of Chlorine. Show your working! IN YOUR BOOKS: • A) Carbon masses of abundance abundance has two isotopes with atomic 12 and 13, Carbon 12 has an of 99% While Carbon 13 has an of 1% calculate the Ar of Carbon. • Magnesium has three stable isotopes: ?? Calculate the Ar of Magnesium A QUICK RECAP: • When we change the number of protons an element has, it changes it’s ____________ and becomes a different ________ • When we change the number of neutrons an element has, it changes it’s ___________ and it becomes an _______ of that element ELECTRON SHELLS • Rules: • A) Each shell has a set capacity that once reached, no more electrons can be placed. That electron starts on a new shell, further away from the nucleus • B) Electrons cannot start a new shell unless the previous one is already full Electron shells Fill up from the centre •Max 2 in first shell •Max 8 in second shell •Max 8 in third shell •More in next shell e.g. Na 11 What are the electron arrangements for :- 6C 12Mg 20 Ca ELECTRON CONFIGURATION STARTER: ISOTOPE RECEP • The element rhenium consists of two isotopes 185Re and 187Re, in the atomic ratio of 2:3. Calculate the relative atomic mass. • Element X has two isotopes, Element 91X has an atomic abundance of 60%. The Ar of element X is 94.6. Using this information find the atomic mass of the other isotope of element X ELECTRON CONFIGURATION • Now that we know how many particles are present in an atom, we need to put the electrons into a regular pattern in their orbits. • This is known as the electron configuration. Electron shells Fill up from the centre •Max 2 in first shell •Max 8 in second shell •Max 8 in third shell •More in next shell •Can’t go to the next shell without filling the lower ones first. IN YOUR BOOKS • Sodium has an atomic number of _____. It has _____ electrons in its atom. • On the 1st shell, there will be ____ electrons. • On the 2nd shell, there will be ____ electrons. • On the 3rd shell, there will be ____ electron. • The configuration for sodium would be __,__,__. • This is a diagram of how the electron configuration of sodium would look like: ANSWERS • Beryllium (2,2) • Sulphur (2,8,6) ANSWERS • Oxygen (2,6) • Potassium (2,8,8,1) ANSWERS • Helium (2) WHAT DO THESE TWO ELEMENTS HAVE IN COMMON? RELATIONSHIP BETWEEN THE ELECTRON CONFIGURATION AND GROUP NUMBER • Look at the configuration of the elements in the question and the group number the element is located. • Do you notice a relationship? • The group number of an element tells us the number of electrons that are on the outer shell of the configuration. • E.g. Oxygen has ____ electrons on the outer shell, it is found in group ____. • However, the elements in Group 0 do not have 0 electrons on the outer shell. Instead, the outer shell is full, so no more electrons can join that shell. • Helium (He) has 2 electrons on the outer shell. It is found in group 0 and not group 2 because only 2 electrons are allowed on the first shell, so it is full!!!! THE PERIODIC TABLE Lo: To learn how to use the periodic table to determine electron configuration STARTER • Draw the electron configuration of Magnesium and label it with it’s electron configuration. • Element X has 6 shells, there are only two electrons on the outer shell. Using your periodic tables Identify the real name of Element X. LETTING THE PERIODIC TABLE DO THE WORK 1 2 4 5 6 Period 3 IN YOUR BOOKS • Group = Columns going along • Period = Rows going down • The group an element is in tells us the number of electrons it has on it’s outer shell while it’s period tells us how many shells it has • For example; Phosphorus would be Group___ Period ___ QUESTIONS: • Iodine can be found in group __ Period __ , meaning it has __ shells and __ electrons on it’s outer shell. • How many electrons would a group 5 element need to gain in order to have a full shell? • How many electrons does Neon have on it’s outer shell? H and He • Helium is the reason we call the last group 0 instead of group 8. All group 0 elements besides He have 8 electrons in their outer shell. • Following the logic so far, what group should we put hydrogen in? SO WHY DON’T WE? • Elements that belong to the same group have similar chemical properties, even if they have different physical properties. • Group 1 metals are all alkali metals, they are all soft to the point they can be cut with a knife and they all react violently with water. PHYSICAL VS CHEMICAL PROPERTIES • Group 1 elements are in the same group, so they have similar chemical properties, but their physical properties are different. • Using the table below construct a bar chart of the melting points of group 1 metals STARTER PHYSICAL AND CHEMICAL PROPERTIES • Physical Properties: Characteristics of a substance that can be observed or measured without changing the chemical nature of the substance • Chemical properties: describes the way that an element or compound reacts chemically with other substances. • Can we think of examples of both? • Thinking back to last lesson, is there any way we can predict the properties of a substance? • The properties of elements show trends as they descend/ascend groups in the periodic table • Using our graphs from last lesson, what would you estimate the melting point of Caesium is? A NEW GRAPH: GROUP 7 Element • Atomic Number Melting o Point (C ) Boiling o Point (C ) ??? ??? Fluorine Chlorine Iodine Astatine PROPERTIES QUIZ IONS 18/12/2018 • What is an electrons charge, mass and location within an atom? • Write out the numbered electron configuration for… a) Sodium b) Oxygen • Ion: An atom or molecule with a net charge due to the loss or gain of at least one electron. For a full outer shell. Charge Mass Location +1 1 Nucleus Neutron neutral 1 Nucleus Electron -1 0 Shells Proton IONS • When an atom needs to lose electrons for a full outer shell, the ion will be positive. • When an atom needs to gain electrons for a full outer shell, the ion will be negative. • E.g. Potassium needs to _____ _ electron for a full outer shell. The ion for Potassium is __. • E.g Nitrogen is in group __, so it needs to gain __ electrons to have a full shell, so the ion for Nitrogen is __ IN YOUR BOOKS. • Work out the ions for the following elements: 1. 2. 3. 4. 5. 6. 7. 8. Magnesium (Mg) Chlorine (Cl) Aluminium (Al) Sulfur (S) Caesium (Cs) Phosphorus (P) Hydrogen (H) Argon (Ar) HOTSEAT! • You have 5 minutes to look over your books at atoms and come up with at least 1 tricky question that you can answer yourself • Our expert in the hotseat must answer any questions asked until the time runs out • If you get a question wrong, our questioner tells us the right answer and becomes our expert. • Whoever is our expert when the time runs our wins a special Christmas prize.