Periodic Periodic Properties and Properties and

TrendsTrendsChm. 1.3.2Chm. 1.3.2

Atomic and Ionic RadiiAtomic and Ionic Radii Atomic Radii – the size of the atomAtomic Radii – the size of the atom

In a Period – L to R, atomic size decreasesIn a Period – L to R, atomic size decreasesWhy?.......as atomic number increases (protons Why?.......as atomic number increases (protons

increase) there is a larger + charge on the increase) there is a larger + charge on the nucleus. The larger the + charge the more the nucleus. The larger the + charge the more the – charged electrons are attracted to it. So the – charged electrons are attracted to it. So the larger nuclei “sucks” the electrons in tighter. larger nuclei “sucks” the electrons in tighter.

In a Group – top to bottom, atomic size In a Group – top to bottom, atomic size increasesincreases

Why?...... Every atom has 1 more energy level Why?...... Every atom has 1 more energy level present than the one before it, so the atoms present than the one before it, so the atoms get biggerget bigger

Atomic and Ionic RadiiAtomic and Ionic Radii Ionic Radii – size of an ionIonic Radii – size of an ion

Cation: + charged ion. It has lost Cation: + charged ion. It has lost electrons so it becomes smaller than electrons so it becomes smaller than the original atom (see next slide)the original atom (see next slide)

Anion: - charged ion. It has gained Anion: - charged ion. It has gained electrons so it is larger than the original electrons so it is larger than the original atom. With an extra -, the balance of atom. With an extra -, the balance of attraction and repulsion is skewed. attraction and repulsion is skewed. Repulsion wins and e- move further Repulsion wins and e- move further from the nucleusfrom the nucleus

Example of Cation Example of Cation becoming smallerbecoming smaller

e-

e-

e-

Atom

e-

e-

e-

Cation

+

Metallic CharacterMetallic Character

Metals tend to to lose e- and become + Metals tend to to lose e- and become + charged cations when they form ionscharged cations when they form ions Is easier to lose valance e- to become stableIs easier to lose valance e- to become stable

Non-Metals tend to gain e- and become – Non-Metals tend to gain e- and become – charged anions when they form ionscharged anions when they form ions Is easier to gain valance e- to become stableIs easier to gain valance e- to become stable

Ionization EnergyIonization Energy

Ionization Energy – the energy required Ionization Energy – the energy required to remove an e- from an atom (to form a to remove an e- from an atom (to form a cation). cation). In a Period – L to R, ionization energy In a Period – L to R, ionization energy

increases. It gets harder to remove e-. increases. It gets harder to remove e-.

Why?...smaller radii, e- are closer to + nucleus. Why?...smaller radii, e- are closer to + nucleus. In a Group – Top to Bottom, ionization energy In a Group – Top to Bottom, ionization energy

decreases it gets easier to remove an e-decreases it gets easier to remove an e-

Why?...larger radii, e- are further from the + Why?...larger radii, e- are further from the + nucleusnucleus

ElectronegativityElectronegativity

Electronegativity – the ability of an atom Electronegativity – the ability of an atom to attract electrons when it is bonded to to attract electrons when it is bonded to another atom in a chemical bond. another atom in a chemical bond. In a Period – L to R, electronegativity In a Period – L to R, electronegativity

increases. Atoms have more attraction for e-increases. Atoms have more attraction for e-

Why?....smaller radii, larger + charged nucleus Why?....smaller radii, larger + charged nucleus has strong pull on electronshas strong pull on electrons

In a Group – top to bottom, electronegativity In a Group – top to bottom, electronegativity decreases or stays the samedecreases or stays the same