ELECTRON CONFIGURATION EX. The following electronic configurations result from the correct use of any of the diagrams given earlier. Magnesium, Mg, 12 electrons: 1s 2 2s 2 2p 6 3s 2 Silicon, Si, 14 electrons: 1s 2 2s 2 2p 6 3s 2 3p 2 Iron, Fe, 26 electrons: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Gallium, Ga, 31 electrons: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 1

NOBLE GAS CONFIGURATIONS With the exception of helium, all noble gases (group VIIIA) have electronic configurations that end with completely filled s and p subshells of the highest occupied shell. These configurations are called noble gas configurations. Noble gas configurations can be used to write electronic configurations in an abbreviated form in which the noble gas symbol enclosed in brackets is used to represent all electrons found in the noble gas configuration.

NOBLE GAS CONFIGURATION EX. Magnesium: [Ne]3s 2 (The symbol [Ne] represents the electronic configuration of neon, 1s 2 2s 2 2p 6.) Iron: [Ar]4s 2 3d 6 (The symbol [Ar] represents the electronic configuration of argon, 1s 2 2s 2 2p 6 3s 2 3p 6.) Gallium: [Ar]4s 2 3d 10 4p 1 (The symbol [Ar] represents the electronic configuration of argon, 1s 2 2s 2 2p 6 3s 2 3p 6.)

ELEMENT CLASSIFICATION The periodic table can be used to classify elements in numerous ways: by Distinguishing Electron. by status as Representative, Transition, or Inner-transition Element. by status as Metal, Nonmetal, or Metalloid.

DISTINGUISHING ELECTRON The distinguishing electron is the last electron listed in the electronic configuration of the element.

ELEMENT CLASSIFICATION Representative elements have an s or p distinguishing electron. Transition elements have an d distinguishing electron. Inner-transition elements have an f distinguishing electron.

METALS, METALLOIDS, & NONMETALS

Properties of elements change in a systematic way within the periodic table. METALLIC AND NONMETALLIC PROPERTIES Most metals have the following properties: high thermal conductivity, high electrical conductivity, ductility, malleability and metallic luster. Most nonmetals have properties opposite those of metals and generally occur as brittle, powdery solids or as gases. PROPERTY TRENDS The Elements of Group VA(15) nitrogenphosphorous arsenicantimony bismuth

METALLOIDS Metalloids are elements that form a diagonal separation zone between metals and nonmetals in the periodic table. Metalloids have properties between those of metals and nonmetals, and often exhibit some characteristic properties of each type.

METALLIC PROPERTY TRENDS Elements in the same period of the periodic table become less metallic and more nonmetallic from left to right across the period. Elements in the same group of the periodic table become more metallic and less nonmetallic from top to bottom down the group.

ATOMIC SIZE TRENDS For representative elements in the same period, atomic size decreases from left to right in the period. For representative elements in the same group, atomic size increases from top to bottom down the group.

REPRESENTATIVE ELEMENT ATOMS

FIRST IONIZATION ENERGY TRENDS The first ionization energy is the energy required to remove one electron from a neutral gaseous atom of an element. For representative elements in the same period, the general trend is an increase from left to right across the period. For representative elements in the same group, the general trend is a decrease from top to bottom down the group.

Based on the photo, what is the trend for chemical reactivity with ethyl alcohol in group 1A(1)? As the atomic number increases in group 1A(1), the chemical reaction becomes more vigorous. The rate of gas formation and the size of the bubbles indicate that reactivity increases from top to bottom in this group. CHEMICAL REACTIVITY TRENDS potassiumsodiumlithium