Unit 4 Chemistry

Covalent bond

Electrons simultaneously attracted by more than one nucleus

Coordinate covalent bond

When the nucleus of one atom attracts 2 electrons while the nucleus of the other attracts none

Bond energy

the average amount of energy needed to break one mole of that particular covalent bond.

Lattice energy

amount of energy released when 1 mole of ionic bonds form

Name geometry and angle(s)

Linear; 180

Name geometry and angle(s)

Trigonal Planar; 120

Name geometry and angle(s)

Bent; <120

Name geometry and angle(s)

Tetrahedral; 109.5

Name geometry and angle(s)

Trigonal Pyramid; <109.5

Name geometry and angle(s)

Bent; <109.5

Name geometry and angle(s)

Trigonal bipyramidal; 90, 120

Name geometry and angle(s)

See-saw; <120, <90

Name geometry and angle(s)

T-structure; <90

Name geometry and angle(s)

Linear; 180

Name geometry and angle(s)

Octahedral; 90, 90

Name geometry and angle(s)

Square pyramidal; 90, <90

Name geometry and angle(s)

Square planar; 90

Which elements are not distorted by hydrogen?

Hydrogen does not distort the atomic orbitals of period 3-7 central atoms, so it doesn't affect the geometry.

Only non-metals in periods _______ can form “extra-octet” structures

3-7

Why can’t period 2 non-metal central atoms form bonds with 5-6 atoms?

They are too small so, they would be too close to terminal atoms and there would be too much repulsions.

Which atoms can form a sub-octet?

Al and B form sextet

Be forms only 2 bonds

Electronegativity

The ability for an atom to attract covalently bonded electrons to itself

Explain bond length.

The greater the bonding e-density (or character/order), the shorter the bond length and the greater the bond strength AND higher the bond energy

Define resonance

when “pi” electrons are shared amongst 3 or more atoms

What are delocalized electrons

the pi electrons that are shared among 3+ atoms

Molecules will exhibit resonance if…

more than one valid Lewis structure can be drawn for the molecule

Visible light spectrometer

Measures the different wavelengths of visible light emitted by a source

What does infrared spectroscopy help find?

The kinds of covalent bonds in an unknown molecule

How does an IR spectrometer work?

It will emit IR radiation to a given molecule which will cause different vibrations for different covalent bonds.

Microwave spectroscopy

Helps determine molecular geometry as well as polarity of a molecule.

How to read mass spectrometry?

Determines the abundance of a certain compound and their fragments

How to read photoelectron spectrometry?

determines the energy needed to eject a given electrons from a source using the photoelectric effect (while all the other electrons are still there)