Remaining Exam 3 content

Why does bonding occur between atoms?

Because atoms are trying to lower their potential energy and obtain a full octet

What are the three main types of bonds?

Ionic, Metallic, Covalent

What type of bond is formed by a metal and non-metal?

Ionic bond

What type of bond is formed by two non-metals?

Covalent bond

What type of bond is formed by two metals?

Metallic bond

How do electrons interact between atoms in a covalent bond?

Electrons are shared

How do electrons interact between atoms in a metallic bond?

Electrons are shared but do not ‘belong’ to any molecule but they are shared in a sea of outer electrons

How do electrons interact between atoms in an ionic bond?

they are transfered not shared

In an ionic bond which gains/loses an electron, the metal or nonmetal?

The metal loses an election, the non-metal gains the electron

On the periodic table where are metals?

Metals are on the left all the way until the staircase

On the periodic table where are metalloid?

Starting under B a staircase until Sb

On the periodic table where are non-metals?

The far right side

How can you remember if metals or non-metals loose/gain electrons?

Metals are on the left of the periodic table, so it is easier for them to lose electrons to gain this lower potential energy

What is lattice energy?

The energy required to go from an ionic solid to gaseous ions

When an ionic solid turns into gaseous ions(lattice energy) is it endo or exothermic?

endothermic(positive delta H)

How do we estimate lattice energy?

Using the Born-harber cycle & understanding of hess’s law

What are the two properties that affect lattice energy?

Size and charge of particles

Coulomb’s Law

the electrostatic interactions between particles A and B is proportional to the product of their changes and inversely proportional to the distance between then

What is the relationship between lattice energy/electrostatic interactions and the charges of the particles?

The product of each particles charge (magnitude) is proportional to the lattice energy

What is the relationship between lattice energy/electrostatic interactions and the charges of the particles?

The distance between the atoms is inversely proportional to the lattice energy

What happens to lattice energy when the product of charges is high?

High lattice energy

What happens to lattice energy when the distance is low?

Higher lattice energy

What is the trend for atom radius?

Left & down - increasing

What is the trend for electronegativity?

Right & up - increasing

What is bond energy?

The energy required to separate atoms that are bonded (overcome electrostatic interactions

When bonds form does it release or absorb energy?

Release energy

When bonds break does it release or absorb energy?

Absorb energy

Is bond energy positive or negative when bonds break?

Positive

Is bond energy positive or negative when bonds form?

Negative

When bonds form is it exothermic or endothermic?

Exothermic

When bonds break is it exothermic or endothermic?

Endothermic

What is bond length?

The distance between nuclei of bonded atoms (when potential energy is the lowest)

What is bond order?

The number of pairs of electrons (Bonds) shared between atoms

How do you calculate bond order(particularly for lewis structure)?

The total number of bonds between two atoms/ the # of resonance structures

What does a higher bond order indicate?

Stronger bonds

What is the relationship between bond length, bond energy, and bond order?

As bond length increases, bond energy decreases, and bond order decreases (think about it all in terms of strength of bonds)

On a potential energy graph where is the bond length and bond energy found?

Where the atoms are in equilibrium(the lowest point)

What is going on in terms of electrostatic interactions when the potential energy of the bond is the lowest?

The attraction and repulsion forces are in equilibrium

What is electronegativity?

The ability of a bonded atom to attract shared electrons

What does a high electronegativity value indicate?

That molecule has a greater attraction for shared electrons

What does electronegativity have to do with bond polarity?

The difference in electronegativity between two atoms determine the polarity of the bond

Polar bonds

when electrons are shared unevenly in a (covalent) bond

What is a bond dipole?

In a bond, a dipole arrow points towards the more electronegative atom

What is the difference in electronegativity for an ionic bond?

2.0

What is the difference in electronegativity for a covalent bond?

<0.5

What is the difference in electronegativity for a polar covalent bond?

0.5-2.0

What does partial ionic character mean?

The more ionic/ closer to ionic the bond is

Is a cation positive or negative?

Positive

Is an anion positive or negative?

Negative

Are single, double or triple bonds the strongest?

Triple

Which is the shortest, single, double, or triple bonds?

triple

What is the octet rule?

Most atoms want to have 8 electrons in their valence shell

Why is the way in which atoms are connected/bonded important?

It determines properties such as melting/ boiling point and polarity

What are the primary general exceptions to the octet rule?

Row 3 and below(expanded octet), columns 3 and 13(incomplete octets), atoms with odd numbers of valence electrons

What atoms specifically often break the octet rule?

H & Li (happy w/ two), and Boron(happy w/ 6)

What is formal charge?

Shows if an atom technically ‘lost’ or ‘gained’ an electron when the bond was formed

How is formal charge calculated?

Valence electrons - (dots + bonds) (for an individual atom)

What is the overall formal charge of a cation?

Positive formal charge

Resonance structures

Multiple equally good versions of the same lewis structure

How do molecular dipoles and bond dipoles relate?

Molecular dipoles are the sum of all the bond dipoles in that molecule

Why do we care about molecular dipoles?

The opposing charges of dipoles are interactive and attract other charges

How does the strength of dipole attractions compare to those of covalent bonds?

Dipoles attractions are much weaker, but can be significant if there are many of them

How do chemists treat C-H bond dipoles?

As nonpolar

What are hybrid orbitals?

Orbitals that are oriented for bonding and sharing electrons

Why do hybrid orbitals form?

To maximize the overlap in bonds

Why is more overlap in orbitals important for bonds?

The more orbital overlap, the stronger the bond will be

How can we use molecular/electron geometry to determine the number of hybrid orbitals?

The number of electron groups is the same as the number of hybrid orbitals

What type of bonds do hybridized orbitals form?

Hybridized orbitals make sigma bonds

What happens with leftover p orbitals that are unhybridized?

They are used to make pi bonds

Are pi bonds or sigma bonds stronger?

Sigma bonds

What pi/sigma bonds make up a single bond?

One sigma bond

What pi/sigma bonds make up a double bond?

One sigma, one pi

What pi/sigma bonds make up a triple bond?

One sigma, two pi

How does the presence of pi bonds affect a molecule?

The structure/molecule is more rigid because pi bonds do not rotate freely

How does the presence of sigma bonds affect a molecule?

Sigma bonds increase reactivity

How do sigma bonds(hybrid orbitals) overlap?

End to end

How do pi bonds(unhybridized orbitals) overlap?

Side to side

Hydrocarbons

large chains of carbons and hydrogens

How does the size of the hydrocarbon affect the properties?

It affects the phase of the substance

What phase is a hydrocarbon with 1-4 carbons?

Gas

What phase is a hydrocarbon with 5-18 carbons?

Liquid

What phase is a hydrocarbon with 16-20 carbons?

Thick liquid

What phase is a hydrocarbon with 20+ carbons?

Solid

What are the three ways to draw organic structures?

Full formula, condensed, or skeleton

What is an isomer?

Structures that have the same molecular formula but different structures(basically like a resonance structure)