U2 - Module 4: Inferring Charge Distribution

Question 1

What are the two periodic trends?

Answer 1

1. Ionization Energy
   - Larger for gases
2. Atomic/Radius Size
   -Large for metals

Question 2

When does nuclear attraction increase?

Answer 2

As the shell size gets smaller.
- Electrons have a stronger bond to the nucleus.

Question 3

What are the properties of chemical compounds influenced by?

Answer 3

How the valence electrons are distributed among different atoms.

Question 4

What can the charge distribution of a molecule be determined by?

Answer 4

The structure of the molecule.

Question 5

What is assumed about molecules and their charges?

Answer 5

That molecules have partial positive and negative charges.

Question 6

What are lone pairs in a molecule considered?

Answer 6

Electron rich regions

Question 7

What do molecules have?

Answer 7

Individual and overall charges

Question 8

Electron Rich Area

Answer 8

• Closer to the nucleus
• Contain mainly electrons
• Negative charge

Question 9

Electron Poor Area

Answer 9

Where less electrons/lone pairs are located

Question 10

What causes some atoms to have stronger attractive forces?

Answer 10

They tend to have unfilled valence energy levels that are lower energy than the same energy level in other atoms.

Question 11

What does it mean when an atom has more filled subshells than an atom that has less filled subshells?

Answer 11

The atom with more filled subshells will require more energy to remove the electrons, rather than one that has less filled.

Question 12

What is the electronegativity trend?

Answer 12

The same as ionization energy
- Higher for gases

Question 13

What does electronegativity help predict?

Answer 13

The partial charges on bonded atoms

Question 14

What does it mean when electronegativity is larger in a given area?

Answer 14

There are more electrons between that given bond.

Question 15

Dipole Moment

Answer 15

The existence of positive (g+) and negative (g-) charges

Question 16

How is the dipole moment represented?

Answer 16

An arrow that points from the positive region to the negative region

Question 17

What is a bond considered if a dipole moment is present?

Answer 17

A polar bond

Question 18

What does polarity of a molecule tell us?

Answer 18

Chemical properties

Question 19

What details of chemical properties are in relation to polarity?

Answer 19

Interactions with other molecules and light

Question 20

Vector Sum

Answer 20

Determines the molecules overall polarity

Question 21

What does it mean when the vector sum is 0?

Answer 21

The molecule is nonpolar

Question 22

What affect do lone pairs have on a molecules electronegativity?

Answer 22

It increases electron density, which can affect shape and polarity.

Question 23

What do bond dipole moments act as?

Answer 23

Vectors; molecular geometry

Question 24

What happens to the electron density in polar molecules?

Answer 24

They have an uneven electron density distribution

Question 25

What relation does symmetry have with molecular polarity?

Answer 25

If a molecule is symmetric and has the same surrounding atoms, it will be nonpolar

Question 26

How can molecules that have no electronegativity difference be polar?

Answer 26

The lone pairs causes different electron densities around each of the atoms, which results in polarity.

Question 27

How is polarity related to tetrahedral shape?

Answer 27

All tetrahedral molecules are nonpolar unless they have different atoms surrounding the central atom.

Question 28

How is poalrity related to trigonal planar shape?

Answer 28

All trigonal planar molecules are nonpolar unless they have different atoms surrounding the central atom, or have lone pairs affecting the electron density.

Question 29

What do nonpolar molecules have?

Answer 29

Fully symmetrical charge distributions

Question 30

How do you draw the molecular dipole moment?

Answer 30

Start from the area of lowest EN, and point the arrow towards the area of highest EN.

Question 31

Hydrocarbons

Answer 31

Molecular compounds that only have hydrogens and carbons present

Question 32

Are hydrocarbons polar or non polar, why?

Answer 32

Nonpolar - EN differences are very small - Symmetrical - No regions of high and low electron density

Question 33

What happens when a functional group is attatched to a hydrocarbon?

Answer 33

The overall molecule becomes polar

Question 34

What 4 things should you analyze to determine if a molecule has a dipole moment or not?

Answer 34

1. Symmetry (draw Lewis Structure) 2. Bond Polarity (EN differences) 3. Lone pair distributions (electron density regions) 4. Overall shape (symmetrical or bent)

Question 35

What does molecular polarity influence?

Answer 35

Interactions with light

Question 36

Greenhouse Effect

Answer 36

The earth has gases that absorb IR which help keep the planet warm by absorbing the solar energy. Energy absorbed is then re-emitted into the earths surface through photons.

Question 37

Greenhouse Gases

Answer 37

Substances that absorb and emit IR radiation

Question 38

What is necessary for a molecule to absorb IR radiation?

Answer 38

There should be a change in its net molecular dipole moment when the molecule vibrates

Question 39

What are the only molecules that are not IR active?

Answer 39

Diatomic Molecules (same element) - Cannot be unevenly stretched/bent

Question 40

Electronegativity

Answer 40

A measure of the ability of an atom in a bond to attract electrons to itself

Question 41

What do differences in electronegativities between atoms create?

Answer 41

Bond polarity due to an unequal distribution of charge