Chem Quiz 4

What are the first 5 prefixes for binary molecular/covalent compound names?

What are the first 5 prefixes for binary molecular/covalent compound names?

di: 2

tri: 3

tetra: 4

penta: 5

hexa: 6

What are the steps for naming binary molecular/covalent compounds?

1st word: name of the first nonmetal in the formula, proceeded by a greek prefix (di, tri) telling how many atoms of the element

2nd word: name of second nonmetal, proceeded by a greek prefix (di, tri) telling how many atoms of the element, with end of name replaced with -ide

Name of PH3?

Phosphorus Trihydride

Name of N2H4?

Dinitrogen Tetrahydride

Name of N2O4?

Dinitrogen Tetraoxide

Steps for naming binary acids?

1. Change hydrogen to hydro-

2. Change end of other nonmetal to -ic

3. Add acid as 2nd word

Name of HF?

Hydrofluoric acid

Name of HCL?

Hydrochloric acid

Name of HBr?

Hydrobromic acid

Name of HI?

Hydroiodic acid

What does the main group number of an element tell us?

number of valence electrons

Ex. Rb - group number: 1, valence electrons: 1

Ex. I - group number: 17, valence electrons: 7

Lewis Symbols for Ions

—>

Lewis Symbols for Ionic Compounds

All these elements once they become ions have valence shells of electrons like the nearest noble gas

What do Lewis Symbols depict?

covalent bonds in Lewis Structures

What are covalent bonds depicted as?

Dashes (—)

What is a single shared paired called?

A single bond

What are electron pairs not involved in bonds called?

lone pairs

What is the octet rule?

main group nonmetals to form enough bonds to have eight valence electrons

What period elements will NEVER surpass the octet rule?

2nd period elements (B, C, N, O, and F)

What is hydrogen’s duet rule?

Hydrogen just needs 1 more electron to have a fully filled shell (wants to be like helium with 2 electrons); WILL NEVER HAVE MORE THAN ONE BOND AND WILL NEVER BE THE CENTRAL ATOM

What are double bonds?

two pairs of electrons (4 total)

What are triple bonds?

three pairs of electrons (6 total)

What are the rules of complicated lewis structures?

DO EXAMPLES ON SLIDES

What are the octet rule exceptions for period 2 elements?

make double bonds where needed

What are the octet rule exceptions for group 1, 2, 13, and 14 elements?

For metals and group 3 elements the goal is a formal charge of 0, not the octet rule (central atoms are electron-deficient and have unfilled octects)

What is the octet rule exceptions for expanded octets?

Central atoms of period 3 and above can have expanded octets (more than 8 electrons around atom)

What are hypervalent molecules?

molecules that contain central atoms with expanded octets

What is a terminal atom?

everything connected to the central atom

What is a free radical

molecule with an odd number of valence electrons, resulting in one unpaired electron

What is an electron deficient/unfilled octet?

a chemical species where a central atom has less than eight electrons in its valence shell

What is formal charge?

the hypothetical charge the atom would have if we could redistribute the bonding electrons equally between atoms

What is the equation of formal charge?

Formal charge = valence electrons - lines(bonds) - dots (electrons)

What can formal charge help predict?

molecular structure

What is a bond angle?

the angle between three contiguous atoms (sharing a common border)

What is bond length?

the distance between bound nuclei

What does the VSEPR theory stand for?

Valence Shell Electron Pair Repulsion

What is the VSEPR theory?

a model used to predict molecular structure based on the number of valence shell electron bond pairs among the atoms in a molecule or ion

What does the VSEPR theory assume?

pairs of electrons want to be as far away from other electrons as possible

What does minimize electron pair - electron pair repulsion mean?

to arrange electron pairs around a central atom in a molecule as far apart as possible from each other, effectively reducing the repulsive forces between them

What do Lewis Structures do?

describe the valence electron configuration of atoms and monatomic ions

What do Lewis Structures and VSEPR Theory predict?

covalent bonds and molecular geometries

What don’t Lewis Structures and VSEPR Theory predict?

1. s & p & d atomic orbitals versus observed bond angles like 120 degrees

2. magnetic behavior of O2 vs magnetic inertness of N2

What is the Valence Bond Theory?

describes a covalent bond as the overlap of half filled atomic orbital

What are the 2 attributes for a covalent bond?

1. 2 orbital must overlap

2. single electrons combine to form an electron pair

The greater the overlap between orbitals, ____________

the stronger the bond

Lower energy = ___________

greater stability

What is the internuclear axis?

orbitals overlap directly between two nuclei

What else matters with bonds?

orientation (s p d f)

What are sigma bonds?

Single bonds are sigma bonds

What are sigma bonds created from?

overlap of s-s, s-p, or p-p atomic orbitals

What are Pi bonds?

In a Pi bond, what is along the axis?

A node where electrons can’t be located (area of zero electron density that exists directly between the two atoms forming the pi bond)

What is a double bond composed of?

1 sigma bond and 1 pi bond

What is a triple bond composed of?

1 sigma bond and 2 pi bond

How many sigma and pi bonds?

9 sigma and 2 pi

How many sigma and pi bonds in each?

NH3: 3 sigma, 0 pi

N2: 1 sigma, 2 pi

3: 7 sigma,

4: 10 sigma, 0 pi

5: 12 sigma, 3 pi

What are the 5 types of orientation of electron pairs?

1. linear

2. trigonal planar

3. tetrahedral

4. trigonal bipyrimidal

5. octahedral

What are the angles of the 5 types of orientation of electron pairs?

1. linear: 180 degrees

2. trigonal planar: 120 degrees

3. tetrahedral: 109.5 degrees

4. trigonal bipyrimidal: 90, 120, 180 degrees

5. octahedral: 90 and 180 degrees

What are caltrops? What molecular geometry do they have?

weapons made of sharp nails or spines that are used to impede the movement of enemies (tetrahedral)

What is the angle of bent or angular with 1 lone pair?

<120 degrees

What is angle of trigonal pyramidal with 1 lone pair?

<109 degrees

What is the angle of bent or angular with 2 lone pairs?

<<109 degrees

Answer on separate piece of paper

What can multicenter molecules do?

can predict the local molecular geometry at each atom on a more complex molecule

What are the molecular geometries of non-H atoms in glycine?

answer

What do polar bonds result in but nonpolar bonds don’t?

a dipole

What is a dipole?

a positive and negative pole (more electronegative atom) in the bond

What do molecular dipole result from?

the sum of all bond dipoles

How is a molecule a polar molecule?

molecule with lone pairs are polar

How is a molecule a nonpolar molecule?

molecules with no lone pairs are nonpolar; linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral

What must a polar molecule have?

1. contain at least 1 polar covalent bond

2. molecular geometry has lone pairs

What are the properties of polar molecules?

1. align when placed in an electric field

2. polar solvent dissolve polar substances (will not dissolve nonpolar substances)