Atomic Mass• Definition: the ~ mass of one atom of an element• Tells us how much one atom weighs in atomic mass units. Mass
Organization of The Periodic Table Group/Family PeriodOrdered by atomic mass. Columns arranged to form groups with similar properties
Assessment• Which element has the greatest atomic mass?• Lithium• Sodium• Potassium• Rubidium
Reactivity• The ease and speed with which an element combines, or reacts, with other elements or compounds Pure sodium reacts explosively with air
Groups/families of elements have similar reactivityGroup 1: metals that react violently with water Group 18: Gases that barely react at allWhy do groups/families of elements react the same way?
Atoms have neutral charge• # of Protons (+) = # of Electrons (-) = 0 charge• Example: Hydrogen• How many electrons does C have?
Electrons orbit in “shells” • 1st shell can fit 2 electrons 1st period/row • 2nd and 3rd shells can fit 8 electrons2nd period/row3rd period/row
Atoms want their shells to be full• 2 electrons in first shell• 8 electrons in 2nd and 3rd shells• Examples:
Question• How many electrons does an oxygen have?• How many electrons are in its outer shell?• Which group is oxygen most likely to react with?
QuestionFor the first 3 periods:1) How many electrons are in the outer shell of each element in group 1? Group 2?Group 13? Group 14? Group 15? Group 16? Group 17? Group 18?2) How many electrons does each element in each group above need to fill itsouter shell?3) Which groups are the most likely to react with one another?4) Which group is least likely to react with any other group?
Only use the 1 3 periods st• For the first 3 periods:• 1) How many electrons are in the outer shell of each element in group 1? Group 2?• Group 13? Group 14? Group 15? Group 16? Group 17? Group 18?• 2) How many electrons does each element in each group above need to fill its• outer shell?• 3) Which groups are the most likely to react with one another?• 4) Which group is least likely to react with any other group?
Take home message• The properties of an element can be predicted from its location on the Periodic Table• This is largely a result of the number of electrons in their outer shell.
Metals• Shiny• Solids (at room temp)• Malleable – can be hammered flat• Ductile – can be pulled into wire• High Conductivity – ability to transfer heat or electricity to another object
Reactivity of Metals High LowMetals will usually lose electrons when they react with other elements
Nonmetals• Opposite of properties of metals• Not shiny• Poor conductors• Mostly gases (at room temperature)• Solids are brittle Sulfur
Reactivity of Nonmetals Low Low HighNonmetals will usually gain or share electrons when they react with other elements
Some Important Nonmetals• Carbon – important element for making up living organisms• Noble Gases – group 18 – very nonreactive. Have full outer shells.
Metalloids• Inbetween metals and nonmetals• Solids (at room temp)• brittle and hard• Semiconductors – can conduct electricity under some conditions but not others. – very important for computer chips• Most common example – Silicon – in sand and glass
Assessment• The atomic number is the number of• valence electrons.• neutrons.• protons in the nucleus.• electrons in the nucleus.
Assessment• The periodic table is a chart of the elements that shows the repeating pattern of their• energies.• properties.• element symbols.• names.
Assessment• Which piece of information cannot be found in a square on the periodic table?• Atomic mass.• Chemical symbol.• Atomic number.• Number of neutrons.
Assessment• Which element will have properties most similar to Calcium?• Potassium.• Scandium.• Magnesium.• Bromine.
Assessment• Which group is most likely to lose/share 2 electrons in a chemical reaction?• 1.• 2.• 17.• 18.
Assessment• Which side of the periodic table contains most of the nonmetals?• Left side.• Right side.• Middle.
Assessment• Which is not a property of nonmetals?• Brittle.• Nonmalleable.• High conductivity.• Most are gases at room temperature
Assessment• Which metal is probably the most reactive?• Potassium• Calcium• Scandium• Titanium
Assessment• Which nonmetal is probably the most reactive?• Nitrogen• Oxygen• Fluorine• Neon