Exploring the Periodic Table Chapter 5.2 Notes

The Role of Electrons The number of valence electrons determines many of the chemical properties of an element Elements in the same group have similar chemical and physical properties because they have the same number of valence electrons Group 1 = 1 valence electron Group 2 = 2 valence electrons Group 13 = 3 valence electrons Group 14 = 4 valence electrons Group 15 = 5 valence electrons Group 16 = 6 valence electrons Group 17 = 7 valence electrons Group 18 = no valence electrons

Location is Related to Electron Arrangement If you know where an element is located on the periodic table, then you can find out how electrons are arranged in the atom The electron arrangement becomes more complex as you move to the right across a period and as you move down along a group

Ion Formation Atoms that do not have full outer orbitals either gain or lose electrons A full outer orbital is 8 electrons Remember that neutral atoms have the same number of protons and electrons; if an atom gains or loses electrons, the atom now has a net electric charge An atom with a charge is called an ion Elements in Group 1 form positive ions Group 1 elements have 1 valence electron, easier for the atom to lose 1 electron than gain 7 Elements in Group 17 form negative ions Group 17 elements have 7 valence electrons, easier for the atom to gain 1 element than lose 7

Ion Formation Positive ions are called cations. Example: Li + Negative ions are called anions. Example: F -

Classifying Elements All elements are either metals, nonmetals, or semiconductors (metalloids)

Families of Elements Chapter 5.3 Notes

Further Classifying Elements Group number Number of valence electrons Name of family 11alkali metals 22alkaline-earth metals 3-12variedtransition metals 177halogens 188noble gases

Metals Metals include the alkali metals, alkaline- earth metals, and transition metals Alkali metals: very reactive, soft, shiny, reacts violently with water Only found in nature combined with other elements because they are so reactive

Metals Alkaline-earth metals: harder, stronger, denser, and have higher melting points than alkali metals Less reactive but still react to form 2+ ions (lose their 2 valence electrons) Transition metals: are even harder, stronger, denser, and have higher melting points (except mercury) than both alkali and alkaline-earth metals Found in the middle of the periodic table

Nonmetals Nonmetals are on the right side of the periodic table (except hydrogen) Include some elements from groups and all of the elements in groups 17 and 18 Noble gases are inert, or unreactive, because they have a full outermost orbital Noble gases do not form with other atoms to make compounds

Nonmetals Halogens (group 17) are the most reactive nonmetals because they have 7 valence electrons Want to gain 1 electron so it has a full outer orbital Combine easily with alkali metals because alkali metals want to lose 1 electron Compounds formed by halogens and alkali metals are called salts

Nonmetals Nonmetals and their compounds are abundant on Earth Oxygen, nitrogen, and sulfur are nonmetals; the most plentiful gases in the air are oxygen and nitrogen Carbon forms many compounds Graphite or diamond in its pure state Hydrogen is normally classified as a nonmetal but it is really in a class of its own Unlike any other element Most abundant element on earth Can react with many other elements

Semiconductors Six elements that are semiconductors (or metalloids) Boron, silicon, germanium, arsenic, antimony, tellurium Have some properties of both metals and nonmetals

Homework Worksheet: “Placing All Your Elements on the Table”