Presentation on theme: "What are the periodic trends?"— Presentation transcript:
1 What are the periodic trends? Atomic radiusIonization energyAffinityelectronegativityShielding affect
2 Atomic radiiDefined as one-half the distance between the nuclei of identical atoms that are bonded together.( draw picture)
3 Trends Radii decreases from left to right across a period. Add protons, add p-e pullIncreases as you go down a familyAdding energy levels, layersException Al- GaTable 5-13 page 141slide
4 Questions In period 3, which has the largest radius Na, Mg, P, Cl In family 2 which has the largest radiusCa, Be, Ba, Sr
5 Ionization EnergyThe energy required to remove an electron from a neutral atom. (first ionization energy)Pg 143 figure 5-15When you remove an electron from a neutral ion you form an ion.Any process that results in the formation of an ion is ionization.
6 Trends Ionization energy increases from left to right across a period. It gets harder and harder to remove an electronRadius is smaller, the pull between nucleus and electron is greater.Noble gas – can’t remove the electron.Dips where electrons double up in an orbital.
7 Trends Ionization energy generally decreases as you go down a family. The radius is larger, the electrons are further away and are therefore held less tightly.Shielding occurs – there are more energy levels that have electrons in them, they shield the outer electrons from the nuclear pull.Show slide
8 Second ionization energy The energy required to remove a second electron from an atom ( ion).Always requires more energy to remove the second and successive electrons than the first.Table 1-3 pg 145
9 practiceElement A has a first ionization energy of 419 kJ/mol. Element B has a first ionization energy of 1000 kJ/mol.Are they in the s or p block?Which will most likely give up their electron?
10 ElectronegativityMeasure of the ability of an atom in a chemical compound to attract electrons.Fluorine assigned a number 4Everything else is based off of that value.
11 Trend Family 18 exception Family 1 is very willing to give up its electrons.Has a noble gas configuration if it doesLoosely heldFamily 17 wants electronsFill the outer energy levelStable
12 TrendAs you go left to right across a period it electronegativity increasesAs you go down a family electronegativity will decreasesShielding affectElectrons are further out, loosely held
13 practiceGiven the elements Ga, Br and Ca which has the highest electronegativity?Given 2s22p5 , 4d105s25p5, and 2s22p2Which is the most electronegative?Which two are in the same family?
14 Affinity and Electronegativity Both affinity and electronegativity measure an atom’s ability to attract electrons.Affinity is the energy change when an atom gains an electronElectronegativity measures the ability of an atom to attract electrons.
15 Electron AffinityThe energy change that occurs when an electron is acquired by a neutral atom.If energy is released when an atom gains an electron, the atom is more stable with the extra electron. This will be represented as a negative numberCl kGroup 17 gains electrons readily.
16 affinityIf energy is required to make the electron ‘stick’, then the atom is less stable.This is represented by a positive number for electron affinity or zero.
17 Stability Atoms will always want the most stable configuration; A noble gas configurationA filled sublevelA half filled sublevel, 1 electron per orbital.
18 practice Given 2s22p5 , 4d105s25p5, and 2s22p2 Which has the highest electron affinity?Which family would you expect to have a greater electron affinity, family 2 or 16?
19 trends Not as regular as other trends. Affinity increases left to right across a period. (electrons are added more easily)Affinity decreases down a family. Electrons add with greater and greater difficulty as you go down a family.Less nuclear attraction – shielding affect
20 Ionic radiiCation – loss of an electron always causes a decrease in atomic radius.Anion – gain of electrons always increases atomic radius
21 Trends Table 5-19 page 149 Ionic radii decreases across a period. Cationic radii decreases across a period then in family 15 radii start to increase.Radii increases down a family.
23 Valence electrons Outer level, highest level electrons. Electrons available to be lost, gained, or shared in the formation of chemical compounds.
24 Section reviewState and discuss the general period and group trends among the main group elements.RadiusFirst ionization energyElectron affinityIonic radiusElectronegativityAmong the main group elements, what is the relationship between the group number and the number of valence electrons?How do the periodic properties of the d block elements compare with hose of the main group elements?
25 Section reviewAmong the main group elements,what is the relationship between the group number and the number of valence electrons?How do the periodic properties of the d block elements compare with hose of the main group elements?