IIIIII Unit 3: Electrons and the Periodic Table CP Chemistry Periodic Table Trends

Periodic Law zWhen elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals. What patterns do you notice? Atomic #s 3, 11, 19 are all alkali metals

zAtomic Radius ysize of atom © 1998 LOGAL Atomic Radius zAtomic Radius yAverage distance in an atom between the nucleus and the outermost electron

Atomic Size Trend zAtomic Size increases down a group yWhy larger going down? xAdding more energy levels. zAtomic Size decreases across a period yWhy smaller across? y Increased nuclear charge (more protons) without additional energy levels pulls e - in closer.

zAtomic Radius yIncreases to the LEFT and DOWN Atomic Radius Fr Smallest biggest

The closer you are to Francium, the larger you will be! Which is larger: a.Rb or Li Rb b.N or Ne N Atomic Size & Radius Examples

Ionization Energy zIonization energy is the amount of energy needed to remove an electron. zM + energy  M +1 + e - zElectrons that are close to the nucleus are hard to remove because they are under a strong force of attraction

Ionization Energy Trend zIonization Energy Increases across a period yWhy? Valence electrons experience a greater nuclear force because they are closer to the nucleus. ySmaller atoms have higher Ionization energy. zIonization Energy Decreases down a group. yWhy? Valence electrons removed are farther from the nucleus because they are in higher energy levels. So not held as tightly. yBigger atoms have lower Ionization energy.

zWhy opposite of atomic radius? yIn small atoms, e - are close to the nucleus where the attraction is stronger ySmall atoms have High IE yBig Atoms have Low IE Ionization Energy Trends

yLowest as you go DOWN and to the LEFT Ionization Energy Fr zBottom right elements WANT to lose an electron to become more stable. High IE Low IE

zFirst Ionization Energy E. Ionization Energy K Na Li Ar Ne He

zWhich would have a higher Ionization energy, Sodium or Chlorine? zChlorine is higher. zChlorine is smaller and has a higher nuclear charge (more protons) = stronger hold on electron = higher energy to take it away. zAlso, remember – Na wants to lose an electron (it is a metal) and Cl wants to gain an electron (non-metal)

Electronegativity zThe ability of an atom to attract an electron. zThe smaller the atom, the more electronegative it is because of a greater nuclear force. (greater coulombic attraction as distance between nucleus and electron is shorter.

Electronegativity Trends zElectronegativity Increases across a period. yWhy? Non-metals such as F, O and N want more electrons to complete their valence shell. ySmaller atoms have greater nuclear charge and thus, more force to attract electrons. yException: Noble gases are not included because they generally do not want to gain electrons. They are already stable.

Electronegativity Trends zElectronegativity Decreases Down a Group yWhy? Atomic size increases and valence electrons are farther from the nucleus. yMore energy levels increases shielding. So the pull from the positive nuclear charge is less. yIn General: xNon-Metals have high Electronegativities xMetals have low Electronegativities

yHighest as you go UP and to the RIGHT towards Fluorine Electronegativity Trends F yRemember- Noble gases not included in this trend!

zIonic Radius yCations (+ ions) the ionic radius is smaller than the original atom. yWhy? There is an increased attraction for the fewer electrons that remain. Ionic Radius Na  Na +

Ionic Radius yFor Anions (– ions) the ionic radius is larger than the original atom. xWhy? The nuclear attraction is less for an increased number of electrons. xExtra electrons repel each other and spread out – larger!) © 2002 Prentice-Hall, Inc. Cl  Cl -1

Practice zWhich atom is larger H or He? zWhich atom has a greater ionization energy, Ca or Sr? zWhich atom is more electronegative, F or Cl? yHydrogen – Smaller nuclear charge yCa – smaller and higher nuclear charge yFluorine – Smaller, less shielding with less energy levels.

zWhich atom has the larger radius? yBe orBa yCa orBr Ba – more energy levels Ca – lower nuclear charge Examples

zWhich atom has the higher 1st I.E.? yNorBi yBa orNe N Ne Examples

zWhich particle has the larger radius? ySorS 2- yAlorAl 3+ S 2- Al Examples

Alkali Metal Reactivity