The Period chart and Its Patterns may seem like a mystery…

CASE OF THE PERIODIC TRENDS!

You find a small scroll of paper… Using your keen intellect, what do you observe? pm= picometer 10-12: it’s a trillionth of a meter!

K 1) What do you notice about elements in the same group? Why? Na 3 levels K 4 Levels 2) As you move down a group, the number of energy levels increase = larger radii

P 3) What is the trend within a period? Cl This time, they both have 3 Energy levels 4) As you move across a period, the elements have more protons. More protons mean a greater nuclear pull and pull the electrons closer to the nucleus = smaller atoms!!

On the back of the note…. There’s a small picture!

It appears to be the sizes of ions

5. How do metals become stable ions? Does that affect their size? (Metal Atoms) (Metal Ions) Why? 6. Metals ions are smaller b/c fewer electrons are in the cloud.

7. How do nonmetals become stable ions? How does that affect size? (Nonmetal Atoms) (Nonmetal Ions) Why? 8. Nonmetals ions are larger b/c more electrons are in the cloud.

Dear gang..hopes this helps! 1) More energy levels means wider/bigger atoms/ions! 2)Within a period, the more protons, the greater the pull from the nucleus = smaller atoms! 3) Metals loses electrons, and become smaller. The more they lose, the smaller it gets. 4) Nonmetals gain electrons, and become larger. The more they gain, the larger it gets! Covertly, Mr. S.

(a) Ca, Mg, Sr (c) C-2, C+2, C (b) K, Ga, Ca SAMPLE PROBLEM Atomic Radii Ranking Elements by Atomic Size from largest to smallest (a) Ca, Mg, Sr (c) C-2, C+2, C (b) K, Ga, Ca SOLUTION: These elements are in Group 2A(2). (a) Sr > Ca > Mg (b) K > Ca > Ga These elements are in Period 4. (c) C-2 > C > C+2 The carbon ion gaining electrons is the largest, the normal atom, and then the ion losing electrons.

Hey gang, You need to know these words to proceed any further Hey gang, You need to know these words to proceed any further! I’ve used disappearing ink… -Mr. S. Electronegativity- how strongly the nucleus an atom pulls another atom’s valence e- in a covalent bond. 1st ionization Energy- how much energy is needed to remove the first valence electron from an atom.

electron nucleus 1st 2nd 3rd 4th The electrons create a “shield” that limits reduce attraction to the outer electrons. The further the e- is, the lower the attraction.

Electronegativity 11) What happens to Electronegativity in a group? 12) It decreases down a group. More energy levels shield the electrons. The attractive forces between the nucleus and electrons decreases.

Electronegativity 13) What happens to E.neg across a period? 14) It increases across a period. More protons = a greater nuclear pull. That means there is a greater attraction and pull on the electrons!

By definition, the ionization energy of an element is the energy needed to remove the outermost, or highest energy, (valence) electron from an atom.

15) What happens to 1st Ionization Energy in a group? 16) The more energy levels, the more shielded the electrons are and it require less energy to remove an electron. Cl F 1139.9 1251.1 1681.0 Br

O F Ne 17) What is the trend in I.E. as you move across a period? 1313.9 1681.0 2080.6 8 9 10 Ne Why? More protons = stronger nuclear pull! The greater the attraction from the nucleus, the more energy is required to remove the electron.

Electron Affinity Electron Affinity is kind of like the opposite of Ionization Energy. Ionization Energy is the change in energy when an atom loses an electron and becomes a positive cation. Who likes to do this? Electron Affinity is the change in energy when an atom gains an electron and becomes a negative anion.

Electron Affinity Think of electron affinity as, who would love to have an extra electron? The greater an atom wants another electron, the greater electron affinity. LOTS OF EXCEPTIONS HERE, but generally as you go right across a period, the atoms have higher electron affinity. As you go down a group, it’s harder to add an electron because of increasing size, so electron affinity decreases.

SAMPLE PROBLEM Ionization Energy Ranking Elements by their Ionization Energies, highest to lowest: (b) S, O, Te 1 2 3 (a) Sb, Te, Sn 1 2 3 SOLUTION: Period 5 elements - IE increases across a period. (a) Te > Sb > Sn (b) O > S > Te These elements are in group 15 and energy decreases as you move down a group.

Moving Top to Bottom Atomic Radius Increases Electronegativity Decreases Ionization Energy Decreases Electron Affinity Decreases The effects are explained by additional energy levels. More energy levels make the atoms larger and shielding decreases the attraction of the electrons.

Moving Left to Right Atomic Radius Decreases Electronegativity Increases Ionization energy Increases Electron Affinity Increases The effects are explained by increasing protons & increasing nuclear pull. The nuclear pull increases attraction to the electrons and brings them closer to the nucleus.

Excellent Job Gang!!! ? THE END