Trends of the Periodic Table• Representative elements (main group) only—

so, transition and inner transition metals are not included in the trends

• Group/family: column of periodic table

• Period: row of the periodic table

Atomic Radius: (atoms without charge) ½ the distance across atom

Decreases left to right (across a period) because of the pull from the nucleus as the outer energy level fills

Increase top to bottom (down a group) because of the additional energy level

Atomic Radius…examples

• What’s bigger?– sodium or chlorine?– hydrogen or potassium?

• What’s smaller?– potassium or nickel?– fluorine or bromine?

Ionization Energy: The energy required to remove the valence electron from an atom

Increases left to right (across period) because the electron is closer to the nucleus

Decrease going down a group because the electron is further from the nucleus

Ionization Energy…examples

• Which has a greater ionization energy?– sodium or chlorine?– hydrogen or potassium?

• Which has a smaller ionization energy?– potassium or nickel?– fluorine or bromine?

Electronegativity: The ability of an atom to attract electrons in a chemical bond

Electronegativity increases across a period Electronegativity decreases down a group

H2.1

Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Na0.9

Mg1.2

Al1.5

Si1.8

P2.1

S2.5

Cl3.0

K0.8

Ca1.0

Ga1.6

Ge1.8

As2.0

Se2.4

Br2.8

Rb0.8

Sr1.0

In1.7

Sn1.8

Sb1.9

Te2.1

I2.5

Cs0.7

Ba0.9

Tl1.8

Pb1.9

Bi1.9

Electronegativity…examples

• Which has a greater electronegativity?– sodium or chlorine?– hydrogen or potassium?

• Which has a smaller electronegativity?– potassium or nickel?– fluorine or bromine?