Honors Chemistry Enloe High SChool Periodic Trends Honors Chemistry Enloe High SChool

Element’s Electron Configuration Elements in the same column have similar valence electron configurations As a result, elements in the same column have similar chemical properties This also helps us understand the periodic trends

Atomic Radius Half the distance between the nuclei of two atoms of the same element that are bonded together Atomic radius decreases as you move from left to right across the periodic table Effective nuclear charge: The net positive charge experienced by an electron in a many electron atom

Atomic Radius Atomic Radius increases as you move down a group in the periodic table This is because the valence electrons are in higher energy levels farther from the nucleus

Atomic Radius

Ionic Radius Cations Anions Cations are smaller than parent atoms Cation sizes generally increase from right to left Cation sizes increase down a family This is caused by having more protons than electrons Anions are larger than parent atoms Anion sizes generally increase from right to left Anion sizes increase down a family This is caused by having more electrons than protons

Atomic/Ionic Radius Examples Select the larger species in each of the following pairs: Kr or Xe Si or P Arrange the following in order of increasing size N3-, O2-, F1-

Ionization Energy Minimum energy required to remove an electron from an isolated gaseous atom Requires more energy as you remove more electrons Ionization energy increases when: Moving left to right across the period Moving from the bottom to the top of a group This is because the attraction between the electrons and the nucleus increases

Ionization Energy Once an atom has filled it’s octet, there is a noticeable increase in ionization energy Na 1st ionization energy is 496 kJ/mol Na 2nd ionization energy is 4,560 kJ/mol This is because a core electron is being removed rather than a valence electron

Ionization Energy Magnesium 1st ionization energy is 738 kJ/mol Aluminum 1st ionization energy is 578 kJ/mol This drop is due to Al having a partially filled p orbital (Think electron configurations)

Ionization Energy Arrange the following in order of increasing first ionization energy: S, Cl, Se, Br Which atom has the lower first ionization energy Al or B O or C

Electronegativity The ability of an atom in a molecule to attract electrons to itself Electronegativity increases when: Moving from left to right across a period Moving from the bottom to the top within a group Caused by the nucleus wanting to hold onto electrons more tightly Electronegativity does not apply to noble gases

Metallic Properties Low ionization energy Low electronegativity Large atomic radius/cation radius Have luster or shine Malleable and ductile Great conductors of heat and electricity Most have fewer than 3 valence electrons

Metallic Character Property used to determine how metallic an element will behave Increases when: Moving from right to left across a period Moving from top to the bottom of a group This can be explained by the periodic trends

Nonmetallic Properties High ionization energy High electronegativity Small atomic/anion radii Dull and brittle solids Poor conductors of heat and electricity Most have 5 or more valence electrons

Nonmetallic Character Property to describe how nonmetallic an element will behave Increases when: Moving from left to right across a period Moving from bottom to top within a group This is due to the periodic trends

Metallic and Nonmetallic Character Which of the following is the more active element: K or Rb Na or Al F or Br As or Se

Oxidation State/Number A positive or negative whole number assigned to an element in an ion or molecule For our purposes it will be the same as the charge for an ion Depends on the number of valence electrons an atom has

Oxidation State/Numbers Some elements can have multiple oxidation numbers Transition metals have multiple oxidation numbers because of the d orbitals Metalloids and other elements along the staircase depend on what they are bonded to

Oxidation States/Number Assign oxidation numbers to the following elements: Ca S Mn As

Electron Configuration for Ions For representative elements we will always add or remove electrons from the highest s or p orbital For transition elements follow this order Highest p, then highest s, and lastly highest d

Electron Configuration for Ions Cations Anions Ion that is positively charged Always lose electrons from the valence shell Metals tend to form cations Ion that is negatively charged Always gain electrons Nonmetals tend to form anions