Topic 3: Elements & the Periodic Table

Organizing the Elements Meet the Elements Elements are organized based on their physical and chemical properties

Each element was named and given a symbol Berzelius (1814) Used letters to represent the element First letter of name, capitalized For elements with the same first letters – add second letter Hydrogen (H), Helium (He), Carbon (C), Cobalt (Co)

Exceptions… Some names are based on Latin names Original elements Gold (Au) – aurum Iron (Fe) – ferrum Lead (Pb) – plumbum Copper (Cu) - cuprum

An Order for the Elements Mendeleev All elements have an atomic mass Mass of one atom Determined mass of each atom by comparing it with the mass of a carbon atom

Elements were organized by listing them in order of increasing atomic mass Eg. Oxygen has more mass than carbon – it comes after carbon Other properties repeat at regular intervals

The Periodic Table: How to Read the Elemental Road Map A) Landmarks for each element Name 2. Symbol

3. Atomic mass Mass of one atom of the element Total mass of PROTONS and NEUTRONS Electrons have essentially no mass Is an average Can be a difference in # of neutrons from atom to atom (isotopes) Usually found below symbol Eg. C = Cr = O = Pb = S = Ca =

4. Atomic number Number of PROTONS in the nucleus of the atom Usually found above symbol Eg. O = C = N = Ca = Fe = B =

What pattern do you see in with respect to atomic number? As you read left to right, atomic number increases ATOMS are NEUTRAL Number of protons = number of electrons Charge balances to 0

# Neutrons = Atomic mass – Atomic Number Using the atomic mass and atomic number you can determine the number of neutrons in any atom # Neutrons = Atomic mass – Atomic Number (Round to the nearest whole #) Eg. Silver Atomic mass = Atomic number = # Neutrons = Eg. Strontium

Use the periodic table to find complete the table below Symbol Name Atomic # Atomic Mass # Protons # Electrons Ba Nickel P 35 12 Uranium 54

The Periodic Table: How to Read the Elemental Road Map Subdivisions of the map Metals Non-metals Metalloids

Metals Found on LEFT side of periodic table Similar physical properties: Shiny, malleable, ductile, conduct heat & electricity All are solids @ room tempEXCEPT mercury (Hg) - liquid

Non-metals Found on RIGHT side of table Similar physical properties: Dull, brittle, insulators (don’t conduct heat or electricity) At room temperature - some gases, some solids; ONLY liquid is bromine (Br)

Metalloids “Dividing line” between metals and non-metals Both metallic and non-metallic properties Shiny or dull, may conduct electricity, poor conductors of heat, brittle, not ductile All solids at room temperature Atomic #s: 5 14 32 33 51 52 84

The Periodic Table: How to Read the Elemental Road Map C) Neighborhoods 1. Families (Groups) Vertical columns #1-18 (L to R) Have similar chemical properties Reactivity increases as you move down the group

Group 1 = Alkali metals Have 1 electron in outer shell Most reactive metals – react when exposed to air and water

Group 2 = Alkaline earth metals Have 2 electrons in outer shell Reactive

Groups 3 – 12 – Transition Metals

Group 17 = Halogens Have 7 electrons in outer shell Most reactive non-metals

Group 18 = Nobel gases Have 8 electrons in outer shell (no unpaired electrons) Most stable elements Unreactive

2. Periods Horizontal rows # 1 – 7 from top to bottom