PHYSICAL SCIENCE CHAPTER 5 THE PERIODIC TABLE

ORGANIZING THE ELEMENTS SECTION 1 ORGANIZING THE ELEMENTS

ORGANIZING THE ELEMENTS Lavoisier grouped known elements into 4 MAJOR CATEGORIES: metals, non-metals, gases, and earths.

MENDELEEV’S PERIODIC TABLE Looking for the best way to organize the elements. HE PROPOSED: that elements with similar properties could be lined up in rows based on increasing mass HIS PREDICTION: that he could use the elements on the table to predict the properties of elements still missing from the table. EVIDENCE: Gallium and Eka-aluminum are considered same element because they are so similar

THE MODERN PERIODIC TABLE SECTION 2 THE MODERN PERIODIC TABLE

MODERN PERIODIC TABLE PERIODIC LAW: elements are arranged by increasing atomic number (# of protons) PERIODS: each row in the table is a period and the number of elements per period varies due to number of available orbitals per energy level GROUPS: each column in the table is a group Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups (families).

ATOMIC MASS ATOMIC MASS IS A VALUE THAT DEPENDS ON THE DISTRIBUTION OF AN ELEMENT’S ISOTOPES IN NATURE AND THE MASSES OF THOSE ISOTOPES. ATOMIC MASS UNITS: is defined as one twelfth of the mass of a carbon-12 atom

CLASSES OF ELEMENTS ELEMENTS ARE CLASSIFIED AS METALS, NON-METALS, AND METALLOIDS. METALS: good conductors of electricity and heat, most are malleable, many are ductile (can be drawn into wire) NON-METALS: poor conductors of electricity or heat, have low boiling points, tend to be gas at room temperature METALLOIDS: have properties of metals and non-metals: good insulator at low temps, good conductor at high temps.

VARIATION ACROSS A PERIOD ACROSS A PERIOD FROM LEFT TO RIGHT, THE ELEMENTS BECOME MORE NON-METALLIC IN THEIR PROPERTIES THEY ALSO DECREASE IN REACTIVITY FROM LEFT TO RIGHT

REPRESENTATIVE GROUPS SECTION 3 REPRESENTATIVE GROUPS

REPRESENATATIVE GROUPS A valence electron: is an electron that is in the highest occupied energy level of an atom STABLE OR NOT? Play a key role in chemical reactions Elemental properties vary across a period because the number of valence electrons increases from left to right Elements in a group have similar properties because they have same number of valence electrons.

GROUP 1A: ALKALI METALS Single valence electron, extremely reactive Found only in compounds The reactivity of alkali metals increases from the top to bottom of group 1A.

GROUP 2A: ALKALINE EARTH METALS 2 valence electrons, harder than metals in group 1A Differences in reactivity of alkaline earth metals is shown in how they react with water. magnesium: when mixed with other metals can be as hard as steel but lighter…bicycle frames Calcium: your body needs it for bones and teeth, Calcium Carbonate (mixture of calcium, carbon and oxygen) is main ingredient in chalk and limestone.

GROUP 3A: BORON FAMILY All elements in 3A have 3 valence electrons This group is made up of two different types of elements: metals and metalloids

GROUP 4A: CARBON FAMILY Contains 4 valence electrons 1 non-metal=carbon 2 metalloids = silicon and germanium 2 metals = tin and lead Except for water, most of the compounds in your body contain carbon.

GROUP 5A: NITROGEN FAMILY Each element in this family has 5 valence electrons 2 non-metals = nitrogen (gas) and phosphorus(solid) 2 metalloids = arsenic and antimony 1 metal = bismuth BESIDES NITROGEN, FERTILIZERS OFTEN CONTAIN PHOSPHORUS.

GROUP 6A: OXYGEN FAMILY OXYGEN IS MOST ABUNDANT ELEMENT IN EARTH’S CRUST 3 non-metals = oxygen, sulfur, and selenium 2 metalloids = tellurium and polonium ALL ELEMENTS IN THIS GROUP HAVE 6 VALENCE ELECTRONS

GROUP 7A: HALOGENS HAS 7 VALENCE ELECTRONS DESPITE PHYSICAL DIFFERENCES, HALOGENS HAVE SIMILAR CHEMICAL PROPERTIES HIGHLY reactive non-metals…fluorine most reactive

GROUP 8A: NOBLE GASES Group has 8 valence electrons Noble gases are colorless and odorless, also very non-reactive Very hard to detect