chemistry: covalent bonds

covalent bond

A chemical bond in which electrons are shared between atoms

covalent vs ionic bonds

An ionic bond is formed when one or more electrons are transferred from one atom to another while a covalent bond forms when electrons are shared between atoms.

molecule

A group of atoms bonded together

what is the difference of electronegativity between covalent and ionic bonds

A covalent bond has an electronegativity difference of less than 2.0, whereas an ionic bond has an EN difference of 2.0 or greater.

what elements are involved in a covalent bond?

two non-metals

what elements are involved in a ionic bond?

metal and nonmetal

what are the seven diatomic elements?

hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine

What do the prefixes (mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca) mean?

One, two, three, four, five, six, seven, eight, nine, ten

what are the prefixes used for?

They are used to indicate the number of atoms in molecules

What is the molecular formula for Ammonia

NH3

what are the water and carbon dioxide molecular formula

H2O and CO2

What are the molecular formulas for carbon monoxide, carbon tetrafluoride, and dihydrogen monosulfide?

CO, CF4, and H2S

How do the properties of molecular compounds differ from those of ionic compounds?

-Molecular compounds usually have low melting and boiling points

-ionic compounds have high MP and BP

-Molecular compounds usually do not conduct electricity when dissolved in water

-whereas ionic compounds do, and molecular compounds can be solid, liquid, or gas at room temp

-Ionic compounds are all solid at room temp

what is the exception to molecular compound properties?

network solids, which are molecular substances with very high MP and BP

What is the octet rule?

Many atoms tend to lose, gain, or share electrons in order to achieve the electron configuration of a noble gas. (Usually this means 8 valence electrons).

How many valence electrons does an atom from Group 13 have? How about Group 14? Group 15? Group 16? Group 17? Group 18?

3, 4, 5, 6, 7, and 8

How many electrons are shared in a single bond? A double bond? A triple bond?

2, 4, and 6

What is a Lewis structure (aka electron dot structure)?

A drawing showing the valence electrons in a molecule. Shared pairs (aka bonds) are usually shown as lines. Lone pairs (aka nonbonding pairs) of electrons are shown as dots.

What is a structural formula?

A Lewis structure that doesn't show dots. Just lines.

What is an unshared pair (aka lone pair)?

A pair of valence electrons that is not part of a covalent bond.

draw a lewis structure for ammonia

draw a lewis structure for water

draw a lewis structure for chlorine

draw a lewis structure for methane (CH4)

draw a lewis structure for phosphorus trichloride (PCl3)

How many bonds does each of these elements like to form: Hydrogen, Nitrogen, Carbon, Oxygen, and Halogens

1, 3, 4, 2, 1

Which of the following molecules has a triple bond?: I2,O2,N2

H2

N2

What is a coordinate covalent bond? How is it drawn?

A pair of shared electrons that comes from one atom. In other words, one atom donates both electrons to form the bond, rather than each atom donating one electron.

What are resonance structures? How are they drawn?

Resonance structures are multiple valid Lewis structures that can be drawn for the same molecule. A double-headed arrow is used to show resonance structures

Which of the following has a coordinate covalent bond?: N2, CO2, CO, NH3

CO

If a molecule has an odd number of valence electrons, what does that tell us about its Lewis structure?

One of its atoms will have an unpaired electron. In other words, the octet rule must be violated.

What is bond energy?

amount of energy required to break a bond

Which type of bond is strongest: single, double, or triple?

triple

Common shapes for molecules

Linear, tetrahedral, trigonal planar, trigonal pyramidal, bent

Tetrahedral shape conditions

Central atom bonded to two other atoms, no lone pairs

Linear shape conditions

Central atom bonded to two other atoms, no lone pairs

Trigonal planar shape conditions

Central atom bonded to three other atoms, no lone pairs

Trigonal pyramidal shape conditions

Central atom bonded to three other atoms, with a lone pair

Bent shape conditions

Central atom bonded to two other atoms, with one or two lone pairs

VSEPR

Valence shell electron pair repulsion

Explanation of VSEPR theory

Pairs of valence electrons repel each other. This is true whether the pairs are bonding or nonbonding. Because of the repulsion, the electron pairs will arrange themselves on opposite sides of the atom, forming symmetrical shapes.

Trigonal planar central atom condition

False. If it has a lone pair, it will be trigonal pyramidal.

Effect of molecular shape on properties

Absolutely true!

Polar Bond

Electrons shared unequally between atoms.

Electronegativity

Atom's tendency to attract electrons.

Tug of War Analogy

Atoms pull on shared electrons, affecting polarity.

Partial Charges

Unequal electron sharing creates positive and negative regions.

Van der Waals Forces

Includes dipole-dipole interactions and dispersion forces.

Dispersion Forces

Intermolecular forces present in all molecules.

Dipole-Dipole Interactions

Attraction between partially positive and negative poles.

Hydrogen Bonds

Strongest intermolecular force, 5% strength of covalent bonds.

Intermolecular Forces

Determine states of matter and molecular shapes.

Molecular State Variation

Different states due to varying dispersion forces.

Network Solid

Giant molecule with all atoms covalently bonded.

Carbon Tetrafluoride

Nonpolar due to symmetrical tetrahedral shape.

Electronegativity Difference

Greater than 0.4 indicates a polar bond.

Lewis Structure

Diagram showing electron arrangement in molecules.

Molecule Polarity

Not always polar despite having polar bonds.

Strength of Dispersion Forces

Increases with the number of electrons.

Diatomic Molecules

Two atoms bonded, affecting physical states.

Sigma bond

Symmetrical molecular orbital around atomic nuclei axis.

Pi bond

Molecular orbital from side-by-side p orbital overlap.

Orbital hybridization

Mixing atomic orbitals to form equivalent hybrids.

sp hybrid orbitals

Formed from one s and one p orbital mixing.

sp2 hybrid orbitals

Formed from one s and two p orbitals mixing.

sp3 hybrid orbitals

Formed from one s and three p orbitals mixing.

Linear shape

Shape created by two sp hybrid orbitals.

Trigonal planar shape

Shape created by three sp2 hybrid orbitals.

Tetrahedral shape

Shape created by four sp3 hybrid orbitals.

Strength comparison

Sigma bonds are stronger than pi bonds.

Length comparison

sp hybrid orbitals are longer than p orbitals.

network solids

solids in which all of the atoms are covalently bonded to each other