Family vs Period Notes Family group columns of element as called groups or families Elements in each family have similar but not identical properties All elements in a family have the same number of valence electrons Periods Each horizontal row of elements is called a period The elements in a period are not alike in properties In fact the property change greatly across every given row Names of some representative elements Several groups of representative elements are known by common names Alkali Metals valence electrons The Alkali family is found in the first column of the periodic table Atoms of the Alkali metals have a single electron in their outermost level in other words 1 They are shiny have the consistency of clay and are easily cut with a knife They are the most reactive medals They react violently with water Alkali metals are never found as free elements in nature They are always bonded with another element Alkaline Earth Metals They are never found uncombined in nature They have to valence electrons Alkaline earth metals include magnesium and calcium among others Transition Metals Transition Elements include those elements in the D block These ate the metals you are probably most familiar with copper tin zinc iron nickel gold They are good conductors of heat and electricity The compound of transition metals are usually brightly colored and are often used to color and silver paints Transition elements have 1 or 2 valence electrons which they lose when they form bonds with other atoms Some transition elements can lose electrons in their next to outermost level Halogen Family never found free in nature The elements in this family are fluorine chlorine bromine iodine and astatine Halogens have 7 valence electrons which explains why they are the most non metals They are Halogen atoms only need to gain 1 electron to fill their outermost energy level They react with alkali metals to form salts Noble Gases Noble gases are colorless gases that are extremely un reactive One important property of the noble gases in their inactivity They are inactive because their Because they do not readily combine with other elements to form compounds the noble gases outermost energy level is full are call inert The family of noble gases includes helium neon argon krypton xenon and random All the noble gases are found in small amounts in the earth s atmosphere Valence Electrons Valence electrons are the electrons in the outer energy level of an atom These are the electrons that are transferred or shared when atoms bond together A trend is a general direction in which something tends to move The elements on the periodic table of elements show many trends in their physical and Periodic Trends chemical properties Across the rows Down the columns Atomic Radius 1 2 the distance between the nuclei of 2 like atoms in a diatomic molecule Atomic radius increases as you move down a group As you go down the group they all have the same valence electron but you add a shell Atomic size increases Atomic radius decreases as you move across a period electrons increase but so do protons Increased nuclear charge pulls the electrons closer to the nucleus The size trend in periods is less pronounced than in groups because of the electron shielding Atomic size decreases effect Shielding Effect Reduction in effective nuclear charge on an electron that is caused by the repulsive forces of other electrons between it and the nucleus In an atom with one electron that electron experiences the dill charge of the positive nucleus However in an atom with many electrons the outer electrons are simultaneously attracted to the positive nucleus and repelled by the negatively charged electrons Adding energy levels and shielding as we go down a column explains almost all the trends in a Adding electrons to same energy level so these trends are mostly explained by increased Adding Energy Levels and Shielding Groups group Periods nuclear charge Ionization Energy Energy is needed to remove an electron from an atom The energy needed to overcome the attraction of the nuclear charge and remove an electron from a gaseous is called the Ionization Energy The first ionization energy decreases as you move down a group The size of the atom increases Electron is farther from the nucleus The first ionization energy increases as you move from left to right across a period Nuclear charge increases while shielding is constant Attraction of the electron to the nucleus increases 2nd 3rd 4th Ionization Energies Subsequent electrons require more energy to remove than the first electron How much more energy is needed depends on what energy levels and orbitals the electrons are in Electronegativity is a measure of an atom s attraction for another atom s electrons Electronegativity Sexy factor Is an arbitrary scale from 0 to 4 Generally metals are electron givers and have low electronegativities Nonmetals are electron takers and have high electronegativities Overall Reactivity This ties all the previous trends together in one package However we must treat metals are the largest since they are the best electron givers The most reactive metals are the largest since they are the best electron givers The most reactive nonmetals are the smallest ones the best electron takers The Octet Rule The goal of most atoms except Hydrogen Lithium and Beryllium is to have an octet or group of 8 electrons in their valence energy level They may accomplish this by either giving electrons away or taking them Metals generally give electrons nonmetals take them from other atoms Atoms that have gained or lost electrons are called ions Ions called anion When an atom gains an electron it is negatively charged more electrons than protons and is In the same way that nonmetal atoms can gain electrons metal atoms can lose electrons They become positively charged cations