Transcript Periodic Properties and Trends

Periodic Properties and
Trends
Chm. 1.3.2
Atomic and Ionic Radii

Atomic Radii – the size of the atom
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
Why?...... Every atom has 1 more energy level present
than the one before it, so the atoms get bigger
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Atomic and Ionic Radii

Ionic Radii – size of an ion

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
Example of Cation becoming smaller
e-
e-
e-
e-
e-
e-
Atom
Cation
+
Metallic Character

Metals tend to to lose e- and become + charged
cations when they form ions


Is easier to lose valance e- to become stable
Non-Metals tend to gain e- and become –
charged anions when they form ions

Is easier to gain valance e- to become stable
Ionization Energy

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-.
Why?...smaller radii, e- are closer to + nucleus.
 In a Group – Top to Bottom, ionization energy
decreases it gets easier to remove an eWhy?...larger radii, e- are further from the + nucleus
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Electronegativity

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 eWhy?....smaller radii, larger + charged nucleus has
strong pull on electrons
 In a Group – top to bottom, electronegativity
decreases or stays the same
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