Keep protons in the nucleus from repelling each other. Atomic Number Mass Number Atomic Mass number of protons determines identity of atom

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1 Module 1 - The Atom page 1 of 5 A: Matter & Energy Matter The Has, can be weighed, takes up space Made of Energy Makes the stuff do things, like move or glow No mass, doesn t take up space B: Atomic Structure An atom is the smallest particle of an element that still has the properties of an element Means Indivisible An atom is made of: Protons Electrons Neutrons Label the Diagram Location nucleus orbitals (outer levels) nucleus Charge + - no charge Symbol p + e - n 0 What it does Size Gives atom its identity Can be lost, gained, or shared to form bonds between atoms Protons and neutrons are the same size. One proton or neutron is like having 2000 electrons. electrons are tiny Keep protons in the nucleus from repelling each other How many protons? How many neutrons? How many electrons? What is the mass number? What is the atomic number? What is the identity of the element? C: Atomic Math Atomic Number Mass Number Atomic Mass number of protons determines identity of atom # protons + # neutrons # neutrons = mass # - atomic # not given in the periodic table mass of 6.02 x atoms (1 mole) of the atom comes close to the mass number Can you determine the mass number for the above elements? What do you need to know to determine the mass number? # neutrons: mass number: # neutrons: mass number:

2 D: Isotopes Means Form Or Type Example: Hydrogen # protons # electrons # neutrons atomic number mass number identity symbol page 2 of 5 are isotopes that are radioactive. An isotope can become radioactive if it has too few or too many neutrons. Ex. hydrogen-3 is radioactive, while hydrogen-1 and hydrogen-2 are stable E: Electrons 1. Bohr-Rutherford (B-R) Diagrams Show how electrons are arranged in an atom Steps: 1) Write the element symbol and draw a circle around it. This represents the nucleus. 2) Look at the row number for the element. Draw this many orbitals (rings) around the nucleus. 3) Determine the number of electrons (look at the atomic number) Place the electrons, in pairs, on the orbitals. When the orbital is full, go to the next orbital full energy levels: When the number of neutrons changes, the changes H2O has two hydrogen atoms heavy water is when the H in H2O is deuterium Two types of isotope notation: 1) name - mass number (ex.hydrogen-1) 2) mass number symbol (ex. 1 H) Can you find the mass number in your periodic table?. To find the mass number you need the number of. The periodic table only tells you the number of protons and electrons. Example: Fluorine Valence Electrons Lewis Diagram Outermost electrons on an atom Symbol with dots representing the number of valence Strongest influence on properties of the atom electrons NOW DO THE PARTIAL PERIODIC TABLE 2. Electron Arrangement In The Periodic Table across a period down a group valence electron pattern orbital pattern 3. Why Atoms Gain Or Lose Electrons Atoms gain or lose electrons to have a totally l or totally outer level Atoms with a totally full or empty outer shell are stable Stable = do not form Ex. have totally full shells Atoms that are close to having a totally full or totally empty outer shell are reactive Reactive = easily form Ex. Group 1: vse -, close to empty valence shell Ex. Group 7: vse -. close to full valence shell

3 E: Electrons (continued) 4. Ions ions are atoms or charged groups of atoms Cation = positive ion, ex. Li+, (NH4) + Anion = negative ion, ex. N 3-, (OH) - How does an atom become charged? it loses or gains are too heavy to move around neutral: # = # # = # atoms are Will the atom gain or lose electrons? # valence electrons closer to 0 lose # valence electrons closer to 8 gain page 3 of 5 charged: # # # # ions are How do we find the charge on an ion? combine the total number of positive charges with the total number of negative charges Calculate the charge: Ex. Magnesium Ex. Nitrogen # valence electrons: Will it gain or lose? Why? ** positive ions don t change their name Atomic #12 # valence electrons: Will it gain or lose? Why? charge: name of ion: ** negative ions end in -ide Atomic #7 Ex. Carbon # valence electrons: Will it gain or lose? Why? When carbon loses electrons: NOW DO THE PERIODIC TABLE OF IONS Summary: Changing the number of neutrons changes the mass of the atom Changing the number of electrons changes the charge of the atom adding electrons creates a negative ion taking electrons away creates a positive ion Changing the number of protons changes the identity of the atom More practice creating ions: Atomic #6 When carbon gains electrons: Atomic #6 Word Bank: charge mass identity positive ion negative #electrons in neutral atom: #protons in neutral atom: Identity of atom: # electrons gained/lost final charge: 7 gained 3 e - 12 loses 2 e bromine gains 1 e -

4 F: The Bohr Model of the Atom Overview: Electrons are in orbitals Distance between the orbitals is fixed Electrons cannot be between orbitals An electron can jump to a higher orbital if and only if it absorbs an amount of energy equal to the distance between the orbitals page 4 of 5 When the electron falls back down, it will release the same amount of energy it absorbed n = energy level nm = nanometers ** shown here is a HYDROGEN atom. The distances between orbitals would be different for a different atom. How far is it between level 1 and 2? nm How much energy does the electron have to absorb to jump from level 1 to level 2? nm When the electron falls back down, how much energy will it release? nm How far is it between level 2 and 3? nm How much energy does the electron have to absorb to jump from level 2 to level 3? nm When the electron falls back down, how much energy will it release? nm Will the electron absorb energy of 400 nm? Why or why not? Electromagnetic Radiation An electron responds to a specific type of energy called electromagnetic radiation (EMR) Travels in waves, and can travel through a (like space) shorter wavelength = wave Wavelengths are measured in (3 gold atoms end to end = 1 nm) Look at the diagram of the Bohr atom above: circle the numbers that show up as colours?

5 F: The Bohr Model of the Atom (continued) page 5 of 5 Remember that an electron only absorbs very specific wavelengths of energy Remember that white light has all the colours of light put together If white light was shined onto some hydrogen atoms, which colours (in nm) would get absorbed? Absorption spectrum: the colours that get by an element when light is shined on the element. The electrons absorb those colours, and jump up to a higher orbital. Emission spectrum: When the electron falls back down, the colours it absorbed get released Every element will have its own emission spectrum. This means that every element will glow a different colour Sodium Lithium Copper Potassium Absorption spectra can be used to determine the makeup of stars and clouds in space.