Bonding

Question 1

Monoatomic molecules

Answer 1

Helium, neon, and argon, noble gasses = elements that show no tendency to combine with either like atoms or other kinds of elements

Question 2

Molecule

Answer 2

the smallest particle of an element or a compound that retains the characteristics of the original substance Ex. Water - triatomoic molecule

Question 3

Ionic Bonds

Answer 3

A 1.7 or greater electronegativity difference between atoms will essentially form an ionic bond. Ions - anions & cations Do not retain the properties of the original atoms Arranged into crystal lattice - high melting point - will not conduct a current of electricity until they are in the molten state

Question 4

Nonpolar covalent bonds

Answer 4

Covalent bonds invovle a sharing of electrons between atoms. Their electronegativity difference is between 0 and 0.4. Are gases, liquids having fairly low boiling points, or solids that melt at relatively low temperatures. Do not conduct an electric current like ionic bonds.

Question 5

Polar covalent bonds

Answer 5

Polar covalent bonds have unequal sharing of electrons. Their electro-negativity difference is between 0.4 and 1.6 Exist in some nonpolar molecules ex. CO2, CH4, and CCl4 –> but they are symmetrically arranged covalent bonds

Question 6

Dipoles

Answer 6

Polar molecules - he whole molecule itself has two distinct ends from a charge perspective. - unequal sharing

Question 7

Metallic bonds

Answer 7

are like positive ions in a “sea” of electrons

Question 8

intermolecular forces

Answer 8

refers to attractions between molecules - van der Waals forces

Question 9

dipole-dipole attraction

Answer 9

(type of van der Waals force) Positive and negative charge distribution at any one instant The force of attraction between polar molecules These attractive forces are less than the full charges carried by ions in ionic crystals

Question 10

London dispersion forces

Answer 10

Weakest of all, Ldf’s are 1/10 the force of most dipole attractions instantaneous dipole–induced dipole forces In both nonpolar and polar molecules

Question 11

hydrogen bonds

Answer 11

A hydrogen bond is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. The hydrogen then has the partial positive charge. Hydrogen bonding elevates the boiling point of H2O above the expected slope

Question 12

Resonance structure

Answer 12

Is a hybrid of the possible drawings because no one Lewis structure can represent the situation Ex. benzene or sulfur trioxide

Question 13

Molecular geometry

Answer 13

the three dimensional arrangement of the molecule’s atoms in space The combination of the polarity of the bonds and the geometry of the molecule determine the moelcular polarity

Question 14

Theories explaining molecular structure

Answer 14

VSEPR theory: uses valence shell electron pair repulsion Hybridization theory: uses changes in the orbitals of the valence electrons

Question 15

VSEPR Theory (Valence Shell Electron Pair Repulsion)

Answer 15

bond angles VSEPR uses as its basis that fact that like charges will orient themselves in such a way as to diminish the repulsion between them. linear arrangement: mutual repulsion of two electron clouds forces them to the opposite sides of a sphere trigonal-planar arrangment: minimum repulsion between three electron pairs occurs when the pairs are at the vertices of an equilateral triangle inscribed in a sphere tetrahedral: four electron pairs are farthest apart at the vertices of a tetrahedron inscribed in a sphere. octahedral: mutual repulsion of six identical electron clouds directs them to the corners of an inscribed regular octahedron. **lone pairs do occupy space, but our description of the observed shape of a molecule refers to the positions of atoms only.

Question 16

Hybridization - molecular configuration

Answer 16

This means that chemists envision that two or more pure atomic orbitals (usually s, p, and d) can be mixed to form two or more new hybrid atomic orbitals that are identical and conform to the known shape of molecules.

sp Hybrid Orbitals:

Question 17

Properties of Ionic Substances

Answer 17

1. In the solid phase at room temp. they do not conduct appreciable electric currents
2. In the liquid phase they are relatively good conductors of electric current. The conductivity of ionic substances is much smaller than that of metallic substances
3. They have realtively high melting and boiling points. There is a wide variation in the properties of different ionic comopounds.
4. They have relatively low volatilites and low vapor pressures. In other words, they do not vaporize readily at room temperature.
5. They are brittle and easily broken when stress is exerted on them.
6. Those that are soluble in water form electrolytic solutions that are good conductors of electricity. There is however a wide range in the solubilities of ionic compounds.

Question 18

Properties of Molecular Crystals and Liquids

Answer 18

1. Neither the liquids nor the oslids conduct electric current appreciably
2. Many exist as gases at room temperature and atomspheric pressure, and many solids and liquids are relatively volatile
3. The melting points of solid cyrstals are relatively low
4. The boiliing point of the liquids are relatively low
5. The oslids are generally soft an dhave a waxy consitsency
6. A large amount of energy is often required to decompose the substance chemically inot simpler substances