1. Periodic Properties and Trends Chm. 1.3.2

2. Atomic and Ionic Radii Atomic Radii – the size of the atom Atomic Radii – the size of the atom In a Period – L to R, atomic size decreases In a Period – L to R, atomic size decreases Why?.......as atomic number increases (protons increase) there is a larger + charge on the nucleus. The larger the + charge the more the – charged electrons are attracted to it. So the larger nuclei “sucks” the electrons in tighter. In a Group – top to bottom, atomic size increases In a Group – top to bottom, atomic size increases Why?...... Every atom has 1 more energy level present than the one before it, so the atoms get bigger

3. Atomic and Ionic Radii Ionic Radii – size of an ion Ionic Radii – size of an ion Cation: + charged ion. It has lost electrons so it becomes smaller than the original atom (see next slide) Cation: + charged ion. It has lost electrons so it becomes smaller than the original atom (see next slide) Anion: - charged ion. It has gained electrons so it is larger than the original atom. With an extra -, the balance of attraction and repulsion is skewed. Repulsion wins and e- move further from the nucleus Anion: - charged ion. It has gained electrons so it is larger than the original atom. With an extra -, the balance of attraction and repulsion is skewed. Repulsion wins and e- move further from the nucleus

4. Example of Cation becoming smaller e- Atom e- Cation +

5. Metallic Character Metals tend to to lose e- and become + charged cations when they form ions Metals tend to to lose e- and become + charged cations when they form ions Is easier to lose valance e- to become stable Is easier to lose valance e- to become stable Non-Metals tend to gain e- and become – charged anions when they form ions Non-Metals tend to gain e- and become – charged anions when they form ions Is easier to gain valance e- to become stable Is easier to gain valance e- to become stable

6. Ionization Energy Ionization Energy – the energy required to remove an e- from an atom (to form a cation). Ionization Energy – the energy required to remove an e- from an atom (to form a cation). In a Period – L to R, ionization energy increases. It gets harder to remove e-. In a Period – L to R, ionization energy increases. It gets harder to remove e-. Why?...smaller radii, e- are closer to + nucleus. In a Group – Top to Bottom, ionization energy decreases it gets easier to remove an e- In a Group – Top to Bottom, ionization energy decreases it gets easier to remove an e- Why?...larger radii, e- are further from the + nucleus

7. Electronegativity Electronegativity – the ability of an atom to attract electrons when it is bonded to another atom in a chemical bond. Electronegativity – the ability of an atom to attract electrons when it is bonded to another atom in a chemical bond. In a Period – L to R, electronegativity increases. Atoms have more attraction for e- In a Period – L to R, electronegativity increases. Atoms have more attraction for e- Why?....smaller radii, larger + charged nucleus has strong pull on electrons In a Group – top to bottom, electronegativity decreases or stays the same In a Group – top to bottom, electronegativity decreases or stays the same