Periodic Trends

Annotations:

• [Image: http://www.chemguide.co.uk/atoms/bonding/pteneg.GIF]

1. Electronegativity is a relative measure of attraction that an atom has for a shared pair of electrons when it covalently bonded with another atom
2. As size of an atom increases, the electronegativity decreases
3. The three most electronegative elements are F, N, and O

Annotations:

• [Image: http://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/Atomic_%26_ionic_radii.svg/300px-Atomic_%26_ionic_radii.svg.png]

1. Positive ions are cations negative ions are anions
2. Cations
   1. Fewer electrons than protons
      1. Therefore they are smaller than parent electron
   2. Across the period, ions contain the same number of electrons
3. Anions
   1. More electrons than protons
      1. Therefore larger than parent atom
   2. Proton number increases across the period

Annotations:

• [Image: http://mcat-review.org/ionization-energy.gif]

1. First ionization energy is the energy required to remove one electron from an atom in its gaseous state
2. The value decreases down the group as the outer electron is further from the nucleus so less energy will be required to remove it
3. Generally the values increase across the period
   1. Tthe extra electrons are filling the same energy level and the extra protons in the nucleus attract this energy level closer - harder to remove

Annotations:

• [Image: http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/images/atomic-radii.jpg]

1. Atomic Radius is the distance from the outermost electron and the nucleus, this can never be exactly known
2. As you go down the group, the outermost electron has more energy - Group 1
3. The electrons closer to the nucleus have a greater pull on them