1 Periodic Table of the Elements
3 Where did it come from? 1869 Demitri Mendeleev Russian chemist who discovered a pattern to the elements Wrote properties on cards Arranged cards according to properties and eventually tried increasing atomic mass A repeating pattern of similar properties then appeared
4 A Periodic Pattern periodic = means happening at regular intervals Ex: Days of the Week Same order every 7 days Elemental properties repeat every seven elements
5 Mendeleev s first try resulted with gaps in the pattern. He predicted elements would fill in the gaps, but they had not yet been discovered. Using the pattern he was able to predict their properties. By 1886, all gaps were filled. His predictions were correct.
6 A Slight Tweak A few elements did not fit the pattern in the table 1914 Henry Moseley British scientist who determined the number of protons (the atomic number) in an atom of each element When elements were arranged by atomic number they all fit Mendeleev s periodic pattern
7 Each Square Contains Atomic Number 6 Chemical Symbol Element s Name Atomic Mass C Carbon 12.0
8 Period vs. Group Period Horizontal rows of elements Properties repeat in a pattern across the period Left Right: elements become less metallic All nonmetals are on the right! Group aka Family Vertical column of elements Elements share chemical and physical properties
9 Break it Down Elements are classified in one of 3 categories depending on their properties. The number of electrons in the outer energy level of an atom helps determine in which category an element belongs. Metals - Nonmetals - Metalloids -
10 Metals Most elements Left of the zigzag line Few electrons in out level Most are solid at room temperature Exception: Mercury is a liquid Properties Shiny Malleable Electrically Conductive Thermally Conductive
11 Nonmetals Right of zigzag line Most have complete sets of electrons in outer level Most are gases at room temperature Properties (opposite of metals) Not shiny Not malleable (break if hit) Poor conductors of electricity and heat
12 Metalloids Border zigzag line 1/2 complete set of electrons in outer level Properties of metals and nonmetals Ex: Tellurium is shiny but is also brittle Ex: Boron is hard like diamonds, but it is brittle. It also is a could conductor of electric currents.
13 Elements of all three categories are made of atoms.
14 What are the parts of an atom? Protons Neutrons Electrons
15 INSIDE THE NUCLEUS Protons Positive Charge Determine atomic number Neutrons Neutral Charge OUTSIDE THE NUCLEUS Electrons Negative Charge Located in energy levels Same as atomic number (atoms aren t +/-) Protons and electrons cancel out!
16 Remember Atoms of elements join together chemically to make compounds. The joining of atoms is called CHEMICAL BONDING. When these bonds form, electrons are shared, gained, or lost by individual atoms.
17 Electrons are Often Shared in a Chemical Reaction to Make Compounds What goes in equals what comes out!
18 Which electrons are shared? VALENCE ELECTRONS: Electrons in the outermost energy level
19 How many valence electrons does an atom have? Determined two ways: 1. Model (electron dot diagram) Just count them up! 2. Periodic Table Elements are grouped based on similar properties Elements in the same group (column) have the same number of valence electrons
20 Group 1-2: Same as group number Group 3-12: No rule Groups 13-18: 10 fewer valence electrons than group number Exception: Helium has only 2 (not 8)
21 To bond or not to bond Atoms with 8 electrons in outer level are not likely to form bonds because level is full Atoms with less than 8 are much more likely to form bonds because they want to fill the outer level Atoms with 1 electron with share with atoms that have only 7.
22 When is two enough? The first energy level in all atoms only holds two electrons. Some atoms have only one energy level. They are full with only two electrons not 8. Hydrogen, Lithium, and Helium Lithium gives one away so it s left with two.
23 How exactly are the particles arranged? Bohr Model of the atom: The 3 rd ring can hold up to 18 e - The 4 th ring and any after can hold up to 32 e - All of the protons and the neutrons in nucleus The 1 st ring can hold up to 2 e - The 2 nd ring can hold up to 8 e -
24 Helpful Rules For Drawing Bohr Models 1. Period number tells the number of energy levels. 2. If an element is in Group 1-it will have 1 valence electron. 3. If an element is in Group 2-it will have 2 valence electrons. 4. If an element is in Group 13-it will have 3 valence electrons. 5. If an element is in Group 14- it will have 4 valence electrons.
25 6. If an element is in Group 15-it will have 5 valence electron. 7. If an element is in Group 16-it will have 6 valence electrons. 8. If an element is in Group 17-it will have 7 valence electrons. 9. If an element is in Group 18- it will have 8 valence electrons. 10. Atoms in elements in Groups 3-12 do not have a rule relating their valence electrons to their group number.
26 To Bond or Not to Bond 1. Valence electrons determine whether an atom forms bonds. 2. Atoms of Noble Gases do not usually form chemical bonds. All Noble Gases have 8 valence electrons (except helium). 3. An atom is considered to be full if the energy level contains 8 electrons. 4. Atom that has fewer than 8 valence electrons is more likely to form bonds than an atom that has 8 valence electrons.
27 FYI: Types of Bonds Ionic: bond that forms when electrons are transferred from one atom to another, which results in a positive ion and a negative ion Covalent: bond formed when atoms share one or more electrons Metallic: bond formed by the attraction between positively charged metal ions and the electrons around them
28 Groups at a Glance Follow along on the last page of your library packet to make sure you have important information for each of the groups in the periodic table. Groups have the same number of?
29 Group 1: Alkali Metals Li, Na, K, Rb, Cs, Fr Most reactive metals because atoms give up their only outer electron easily 1 electron in outer level Only found in nature combined with other elements Properties: soft, color of silver, shiny, low density Pure metals often stored in oil-keeps from reacting with water or oxygen
30 Group 2: Alkaline-Earth Metals Be, Mg, Ca, Sr, Ba, Ra Not as reactive because they have 2 outer electrons that are not shared as easily as just one Properties: color of silver, higher densities than alkali metals
31 Groups 3-12: Transition Metals Less reactive than groups 1-2 because they do not share electrons easily Properties Vary Widely: Shiny, conductors of electric and thermal currents, higher densities and melting points than groups 1-2 (except mercury) Most solid, but mercury is liquid Most silver, but gold is gold Some are not reactive (titanium used in medicine), but iron is very reactive (forms rust)
32 Lanthanides and Actinides Periods 6 and 7. Found at bottom of periodic table to keep table from being too wide. Transition metals Lanthanides: Shiny, reactive metals Actinides: Radioactive or unstable (change into atoms of another element) Elements after Plutonium do not occur in nature.
33 Group 13: Boron Group B = One metalloid Al, Ga, In, Tl = Four metals 3 electrons in outer level Very reactive Properties: solid at room temperature Aluminum is most common (earth s crust)
34 Group 14: Carbon Group C = one nonmetal Si, Ge = two metalloids Sn, Pb = two metals Uuq = name to be determined 4 electrons in outer level Properties: solid at room temp and reactivity varies Si and Ge used to make computer chips
35 Group 15: Nitrogen Group N, P = two nonmetals As, Sb = two metalloids Bi = one metal 5 electrons in outer level Nitrogen = 80% of air you breath, fertilizers Properties: solid at room temp. (except N) Reactivity varies among elements.
36 Group 16: Oxygen Group O, S, Se = Three nonmetals Te = One metalloid Po = One metal 6 electrons in outer level Properties: All but oxygen are solid at room temperature. Reactive. Oxygen makes up about 20% of the air you breath!
37 Group 17: Halogens F, Cl, Br, I, At All nonmetals, very reactive Seven electrons in outer energy level so only need one to have a complete set (8) Combine with most metals to form salts Properties: Poor conductors of electric current, violent reactions with alkali metals to form salts, never uncombined in nature
38 Group 18: Noble Gases He, Ne, Ar, Kr, Xe, Rn All nonmetals Very unreactive because they have 8 electrons in outer energy level (except helium which has 2) Properties: colorless, odorless gases at room temperature. Unreactive
39 Hydrogen Most abundant element in the universe Put above group 1 because it only has one electron in the outer energy level, but properties are unlike any single group Properties: colorless, odorless gas at room temperature; low density; explosive reactions with oxygen