For Test #7: The Periodic Table

The Periodic Table 1)Dimitri Mendeleev – 1st to publish a periodic table. 2) The Periodic Law: When arranged by increasing atomic number, the elements display a regular and repeating pattern of chemical and physical properties.

Groups vs Periods Groups – contain elements with similar chemical properties (vertical columns) because they all have the same number of valence (outer shell) electrons. Periods – contains elements with the same number of occupied energy levels. Their chemical properties vary. Note: Know special group names

Can YOU name the special groups?

Phases of Elements Most Reactive Metal Most reactive nonmetal Liquids Gases

Reading the Periodic Table: Classification Nonmetals, Metals, Metalloids, Noble gases Classes of Elements

1) Which is the more reactive metal? A) Potassium or cesium? B) Calcium or barium? 2) Which is the more reactive nonmetal? A) Iodine or Chlorine? B) Carbon or Oxygen?

Diatomic vs Monoatomic Elements Diatomic Elements H O F Br I N Cl Monatomic Elements Noble gases & all the others if not in a compound

Reading the Periodic Table: Classification Nonmetals, Metals, Metalloids, Noble gases Can you name the symbols for the gases?

Reading the Periodic Table: Classification Nonmetals, Metals, Metalloids, Noble gases Can you name the metalloids?

Reading the Periodic Table: Classification Nonmetals, Metals, Metalloids, Noble gases Can you name the 2 liquid elements?

Atomic Radius Atomic Radius is the distance from the center of an atom to its outermost electron shell. Values on Table S Units are picometers (pm)

1)Atomic Radius increases as you move down a group because there are more shells of electrons. 2)Atomic Radius decreases as you move to the right across a period because the nuclear charge increases & pulls the electrons in closer to the nucleus. Atomic Radius Trends Bigger Smaller

Metal Ions Metal tends to give up electrons and form smaller sized ions that are positively charged. Atom Ion

Nonmetal Ions Nonmetals tend to gain electrons and form larger sized ions that are negatively charged. Atom Ion

Isoelectronic Series All contain same total # of electrons Example: 8 O -2 9 F Ne 11 Na Mg +2 How many electrons in each? Which has the largest ionic radius? ~~The one with the most negative charge~~ because they all have the same number of filled shells but the most negative one always has the smallest nuclear charge

You Try Kr Br -1 Sr +2 Rb +1 Are they isoelectronic? Which is largest in radius? K +1 Na +1 Rb +1 Na +1 Are they isoelectronic? Which is largest in radius?

Ionization Energy Ionization energy is the amount of energy needed to pull an electron from an gaseous atom. Values on Table S Units are kilojoules per mole (kJ/mol) It takes more energy to pull electrons off smaller atoms. Trends are opposite of that for atomic radius.

Ionization Energy Trends 1) Ionization Energy decreases as you move down a group. 2) Ionization Energy increases as you move to the right across a period. Bigger Smaller

Know the Ionization Energy Exceptions as you move across any Period and WHY **Group 13 – The reason is ‘Shielding of p1 electron by s2 electrons ’ The s 2 electrons shield the p 1 electron from the full effective nuclear charge making it easier to remove an electron and so it takes less energy **Group 16 – The reason is ‘Electron-pair Repulsion’ Electron-pair repulsion in the p 4 configuration makes it easier to remove an electron and so it takes less ionization energy **Groups 3 to 12: The Transition Metals – The reason is that they have an incomplete d sublevel’ which causes many irregularities

Ionization Energy Trends

Which of the following atoms has the largest first ionization energy? 1)Br, Cl, P, I 2) K, Rb, Sr, Ca

Electronegativity Electronegativity measures how much an atom attracts shared electrons in a chemical bond (“electron attraction”) Linus Pauling – created the electronegativity scale with fluorine having the largest attraction for electrons and it is assigned the biggest value of 4.0 Values on Table S (no units)

Electronegativity Trends Same as ionization energy Reason: If it takes a lot of energy to remove an electron, the atom must have a big attraction for the electron. Bigger Smaller

Which of the following atoms has the largest attraction for shared electrons? 1) Mg, Ni, S 2) Ba, Cl, Cd

Electron Affinity A measure of the energy change that occurs when an electron is added to an atom Trends – Only one to know: As you move across a period  More Negative

Summary Atomic Radius decreases Nuclear Charge increases Electronegativity increases Ionization Energy increases Electron Affinity becomes more negative Atomic Radius increasesNuclear Charge is constantIonization energy decreasesElectronegativity decreases

Don’t Forget How to find #p, #e, #n #p = atomic number #e = atomic number #n = mass number minus atomic number