Chem-Is-Try Key

Periodic Trends and Bonding

1. size: Zn<Cd<Hg IE, EN: Hg<Cd<Zn

size: F, S, Se, As, Sn IE, EN: opposite order

2. Electron shielding- the reduction in the attraction of the nucleus due to the presence of electron shells between the nucleus and the electrons of interestNuclear charge- the number of protons in the nucleus- determines the attraction of the nucleus for the electrons. These two trends determine all other trends because they explain the force of the nucleus on electrons. Electron shielding increases going down a group and does not change across a period. Nuclear charge increases going across a period and down a group, but we focus on the change across a period.

3. electronegativity increases across a period and decreases down a group

Ionization energy increases across a period and decreases down a group

Atomic radius decreases across a period and increases down a group

4…cations differ from the size of the neutral atoms because they lose electrons, reducing the electron shielding and increasing the pull of the nucleus for the electrons

Anions differ from the size of the neutral atoms because they gain electrons, increasing the number of electrons the nucleus must attract, which decreases the pull of the nucleus for each electron

5. Answer:

	SOCl₂	NO (a radical)
	3 Lewis, 1 shape, 1 polarity
Shape:	trigonal pyramidal	linear
Polar or non-polar:	polar	polar
	H₂O	BeCl₂

Shape:	bent or angular	linear
Polar or non-polar:	polar	non-polar

6. Answer:

	AlCl₃	XeF₄	SO₂

Shape:	trigonal planar	square planar	bent or angular
Polar or non-polar:	non-polar	non-polar	polar

	CH₂Cl₂	NH₃	PF₅

Shape:	tetrahedral	trigonal pyramidal	trigonal bipyramidal
Polar or non-polar:	polar	polar	non-polar

trigonal pyramidal