13 Electron Configurations in Groups Elements can be sorted into noble gases, representative elements, transition metals, inner transition metals based on their electron configurationsEvery element ends in the same last term in the electron configuration
14 Representative Elements Groups 1,2,13,14,15,16,17Called representative elements because they display a wide range of physical and chemical properties
15 Transition ElementsIn atoms of a transition metal, the highest occupied s sublevel and a nearby d sublevel contain electrons.These elements are characterized by the presence of electrons in the d orbitalsInner transition elements contain unfilled f orbitals
16 Periodic TrendsAtomic radius – ½ the distance between the nuclei of two atoms of the same element when the atoms are joinedExtremely small – measured in picometersAtomic size (radius) increases from top to bottom within a group and decreases from left to right across a period.
17 Periodic Trends Atomic radius – WHY??? Group trends – as the atomic number increases within a group, the charge on the nucleus increases and the number of occupied energy levels increases.The increase in positive charge draws the electrons closer to the nucleusThe increase in the number of occupied orbitals shields the electrons in the highest occupied energy level from the attraction of the protons in the nucleus.
18 Periodic Trends Atomic Size – WHY???? Periodic trends – each element has one more proton and one more electron that then preceding element.Across a period, the electrons are added to the same principal energy level. The shielding effect is constant for all the elements in a periodThe increasing nuclear charge pulls the electrons in the highest occupied energy level closer to the nucleus and the atomic size decreases
20 IonsPositive and negative ions form when electrons are transferred between atoms\Metals form cations – they lose electrons to form a positive chargeNonmetals form anions – they gain electrons to form a negative charge
22 Periodic TrendsIonization Energy – the energy required to remove an electron from an atomMeasured in the gaseous stateThe energy required to remove the first electron – first ionization energyThe energy required to remove the second electron – second ionization energyThe energy required to remove the third electron – third ionization energy
23 Periodic Trends Ionization Energy Can help you predict what ions will formThe first ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period
25 Periodic Trends Ionization Energy – WHY???? Atomic size increases as the atomic number increases within a group. As the size of the atom increases, nuclear charge has a smaller effect on the electrons in the highest occupied energy level. So less energy is required to remove an electron
26 Periodic Trends Ionization Energy – WHY???? The nuclear charge increases across the period, but the shielding effect remains constant. So there is an increase in the attraction of the nucleus for an electron. Thus, it takes more energy to remove an electron from an atom
34 Periodic TrendsElectronegativity – the ability of an atom of an element to attract electrons when the atom is in a compound
35 Periodic TrendsElectronegativity – decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a periodMetals have low valuesNonmetals have higher valuesFluorine – highest with value of 4