Periodic Table Trends

1. Atomic Radius - the electron cloud surrounding the nucleus is based on probability and does not have a clearly defined edge. - Generally, the total distance from an atoms nucleus to its outer most shell  

- Moving from L  R the atomic radius decreases Trend within Periods - Moving from L  R the atomic radius decreases - As we look from left to right the positive charge in the nucleus increases which increases the attraction between the protons and electrons - True, we do add more electrons as well but not another shell   13 pulling tighter 17 pulling tighter

Trend Down a Group The atomic radius increases moving down a group More protons are added, more electrons are added, but are placed in another shell - Some electrons might “shield” other electrons from proton attraction

Shielding: repulsion between two or more negative electrons in various shells causes the shells to be further away and therefore less strongly connected to the nucleus

Exception: Hydrogen has the smallest atomic radius

2. Ionization Energy Trend Atoms can gain or lose 1 or more electrons to form ions Ion: is an atom or a bonded group of atoms that have a positive or negative charge Cations are positively charged, meaning that they have lost electrons - When atoms lose electrons, they always become smaller

- Anions are negatively charged, meaning they have gained electrons - The protons need to distribute an attraction over a greater number of electrons making the attractions a bit weaker than that of the neutral atom - Anions have a greater atomic radius than neutral atoms

Ionization Energy: the energy required to remove an electron   1st Ionization energy: the amount of energy to remove the 1st electron 2nd Ionization energy: the amount of energy to remove the 2nd electron - More energy is required to remove the 2nd electron than that of the first. This is because the 1st electron would have been experiencing more shielding and a lesser attraction to the positive nucleus 1st Ionization energy 2nd Ionization Energy

increases moving from L  R Trend within Periods increases moving from L  R Just like atomic radius, As we look from left to right the positive charge in the nucleus increases which increases the attraction between the protons and electrons - Therefore, it takes more energy to pry them away   13 pulling tighter 17 pulling tighter Not as strong of a pull, so it is easier to pull one away

Trend Down a Group ionization energy decreases moving down a group More protons are added, more electrons are added, but are placed in another shell Some electrons might “shield” other electrons from proton attraction - This means it takes less energy to remove an electron

Mom has too many kids to watch and can’t keep a close eye on them all as she has less kids to watch, it would be more difficult to nab them

increases when moving left to right 3. Electronegativity Electronegativity: is an atoms ability to attract the electrons of another atom to it Trend Within Periods increases when moving left to right - this is because as we move to the right of the periodic table, the atoms ability to attract electrons becomes stronger as they become closer to a full octet   Boron still needs 5 e- to have a full octet Flourine only needs 1 e- to have a full octet

- decreases as you go down a group Trend Down a Group - decreases as you go down a group - (F) is the most electronegative element   EXCEPTION: Nobel gases have a full octet and are not looking to add e-

4. Metallic Character Trend for Metals Metallic Character – how readily an atom can lose an electron   Trend Within Period From L  R Metallic Character decreases because the attraction between electrons and - the nucleus is stronger - This makes it more difficult to lose an electron Example: Which element is more likely to lose electrons? Lose 4? Lose 1?

Trend Down a Group Metallic Character increases down a group Again, like atomic radius trend, More protons are added, more electrons are added, but are placed in another shell Some electrons might “shield” other electrons from proton attraction - This makes it easier for an electron to be lost

5. Reactivity for Metals Trend Reactivity: how likely or vigorously an atom is to react with other substances Usually determined by how easily electrons can be removed (Same as Metal Character)   Trend Within Period - From L  R reactivity decreases because the attraction between electrons and the nucleus is stronger -This makes it more difficult to lose an electron, therefore less reactive

Halogen Reactivity Trend Down a Group Reactivity increases down a group Again, like atomic radius trend, More protons are added, more electrons are added, but are placed in another shell -Some electrons might “shield” other electrons from proton attraction - This makes it easier for an electron to be lost, or become more reactive   Halogen Reactivity

Reactivity Reactivity