Chemistry Unit 4: Periodic Trends

When does it get harder to remove successive electrons?

For every electron removed, each electron after gets harder to remove for an ion

Ionization energy decreases when?

As radius increases

When does nuclear charge felt by valence increase?

across the row

• larger effective nuclear charge pulls valence shell closer to nucleus

• addition of electron to valence shell repels but doesn’t shield as well as if it were added to the core

• greater nucleus charge happens so electrons are brought closer to nucleus

What happens to the radius of ions of an element (nuclear charge fixed)

• radius increases with increasing # of electrons

What happens to radius of ions or atoms with the same # of electrons

• isoelectronic species

• increases with decreasing nuclear charge

Largest cation

• Rb+

• Cs+

• smaller than anions

Smallest anion

F-

The larger the positive charge…

The smaller the cation

• for isoelectronic

The larger the negative charge…

The larger the ion

• more negative repels electrons so theyre bigger

• more positive attracts electrons and hold closer so radius smaller

Ionization energy

• energy needed to eject an electron

• must be (g)

• Increases left to right

• decreases moving down

Filled and half filled subshells

• electrons are harder to remove

• have special stability

Metals properties

• conductive, high melting/boiling point, ductile, mallaeble, shiny

• metal + Oxygen = basic —> form cation

• metal + non metal —> metal loses electrons

• most metallic = bottom left of periodic table

which elements are liquid at room temp

Br and Hg

WHich class of metals have highest melting points

Transition metals + Carbon

WHich elements are the most dense

Gets more dense going from top → bottom

• most dense is the transition metals

Polar vs non polar covalent

electronegativity:

0.5<= x <= 2 → polar covalent (2 nonmetals)

>2 → ionic bond

<0.5 → non-polar covalent

= 0 → pure covalent bond (02, N2, etc)

reactivity of metals

• Alkalai metals: down periodic table = more reactive

• halogens: down periodic table = less reactive

Acidity of oxides

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CANADA (saskatchewan)