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Chemistry 10th Grade
Chapter 8 Test
| Question | Answer |
|---|---|
| models used to indicate the molecular shape | ball and stick models |
| what does the ball represent | the atom's nucleus and inner level electrons |
| what do the straight sticks represent | single bonds |
| what do the curved springs represent | multiple bonds |
| The shapes of the molecule must be | symmetrical |
| What does symmetrical mean in this case | the bonds and atoms must be in a regular pattern with equal distances separating the atoms that are not bonded to each other |
| why are they arranged symmetrically | because it is based on the valence electrons which have the same charge and same charged particles repel each other |
| what is the VSEPR theory | It is the valence shell electron pair repulsion theory |
| what is the theory of the VSEPR theory | in small molecules, the pairs of valence electrons are arranged as far apart from each other as possible |
| Molecules that contain _____________________ do not follow the VSEPR theory | transition metals |
| Molecules that contain only 2 atoms are connected in what pattern or form | Linear |
| Are all linear molecules made of just two atoms | No, some contain three such as CO2 |
| we can discuss the ways bonds are arranged by looking at the the ______ ________ | bond angles |
| What are bond angles | the geometric angle between 2 adjacent (next to each other) bonds |
| a straight line has a bond angle of | 180 degrees |
| a molecule that is trigonal planar has what shape | a flat triangle shape |
| a tetraheral shape has how many sides | four |
| what shape does a water molecule have | bent |
| sometimes when one atom approached another atom, the orbitals may be perturbed or changed and the orbitals of the two mix and form a | hybrid orbital |
| in a linear molecule, when a hybrid orbital is formed, what two orbitals are mixed and what is it now called | the S and the P orbitals mix and it is called a SP orbital |
| in a trigonal planar molcule the mixing of orbitals involve what orbitals | the S orbital and two P orbitals called the SPsquared orbital |
| in the ball and stick models, the molecules are drawn with all the sticks being the same size...is this true in real life molecules | No..the bonds may have different lengths |
| as you move down a group in a periodic table, what happens to the bonds | they get longer |
| multiple bonds are longer or shorter than single bonds | shorter |
| why are the bonds shorter in multiple bonds | there are more electrons and because of this, they have a stronger electrical bond to the nuclei |
| what are the 5 common shapes of molecules | Linear, trigonal planar, tetrahedral, pyramidal, and bent |
| polar bonds are also known as | dipoles because they have two charged ends |
| molecules composed of one kind of atom are | nonpolar molecules |
| to determine whether a molecule is polar you can look at the ________ of the molecule | shape |
| CO2 is made of polar bonds but is not a polar molecule, why? | because the positive charge is in the middle of the three atoms and both poles (ends) are negative |
| Water is a polar molecule because its shape is _______ which gives it a positive and negative end | bent |
| the shape of a small molecule helps to determine the molecules polarity but what happens in a large molecule | the polarity determines the shape (opposite of small molecule) |
| what 2 things determine the polarity of a molecule | the polarity of its bonds and the shape |
| These are properties of a substance that result from forces between molecules | intermolecular forces |
| the type and strength of these forces determine what about a substance | is it a gas, liquid , solid and will it dissolve in water or another solvent |
| what two forces affect the boiling points of substances | molecular weight and intermolecular forces |
| Intermolecular forces can be divided into 3 categories...they are | dipole-dipole, London forces and hydrogen bonds |
| when are dipole-dipole present | only between polar molecules |
| which force affects every type of molecule | London forces |
| hydrogen bonds are only present between molecules containing certain types of_________________________ | polar bonds |
| dipole molecules have positive and negative charged ends because of what | unequal sharing of electrons in covalent bonds |
| forces between neighboring polar molecules due to the attraction of oppositely charged ends are called _________ and are present in all polar molecules | dipole-dipole forces |
| Hoe come dipole-dipole forces are not as strong as ionic bonds | they do not have the "full charges" like ionic compounds do |
| as the polarity of molecules increase, what else increases | the boiling point |
| Generally, the more polar the molecule, the greater the ________________, the higher the boiling point | dipole-dipole force |
| for atoms or molecules in the gaseous state to condense to the liquid state, there must be a force of attraction between the atoms or molecules, this is called___________________________ | London Forces |
| Who came up with this theory | Fritz London in 1930 |
| London forces are the only type of intermolecular force that affects______________________ | nonpolar molecules |
| nonpolar molecules do not have neg and pos ends but have a uniform electron density and charge. This uniformity is an average but there are brief times the electrons are not uniform but are distorted or deformed and the molecule becomes a | dipole--meaning one end has a slight but quick negative charge and the other has a slight but quick positive charge |
| when these dipoles happen in non polar molecules they are quick and attract each other with a | London force---and it is very weak |
| Because they occur because the electron cloud is distributed or "dispersed", London forces are also called | dispersion forces |
| the more easily an electron cloud is distorted is a property called | polarizability |
| the more polarizability the greater the strength of the | London forces |
| If the molecular size increases, what happens to the London Force | it is stronger |
| boiling points for similar compounds tend to _________ with the molar mass because the intermolecular forces are stronger | increase |
| when an atom such as oxygen, nitrogen or fluorine pulls the electrons away from hydrogen, the hydrogen becomes positive and the other atom becomes negative. they form a | hydrogen bond |
| The hydrogen bond causes dipoles to be | unusually strong |
| a hydrogen bond is not an actual true bond but it is a strong | intermolecular force |
| hydrogen bonds are only _____ to _______ percent as strong as a covalent bond | 5 to 10 percent |
| hydrogen bonds are much ___________________ than other intremolecular bonds | stronger |
| how are hydrogen bonds represented in a drawing | dashed lines between molecules |
| hydrogen bonds are very important. the properties of ______ and _____, the structure and function of _________ and _____ are due to hydrogen bonds | water and ice proteins and DNA |
| solids are classified into 2 types | amorphous solids and crystalline solids |
| solids that have no ordered arrangement or pattern for the particles that compose them are called | amorphous solids |
| solids that are arranged in a regular and repeated three dimensional pattern | crystalline solids |
| amorphous solids do not have a what | definite melting point...examples, butter, glass, tar..but they become viscous (syrupy) |
| crystalline solids have a definite | boiling point |
| the simplest repeating unit in a crystal is called | unit cell |
| if you extend the unit cell in 3 dimensions, it results in | definite angles and specific planes--sort of like wallpaper |
| a crystal has how many different type of classifications | 7---cubic, tetragonal, hexagonal, rhombohedral, orthorhombic, monoclinic, triclinic |
| the simplest classification to study is the | cubic |
| ionic bonds hold what together | ionic solids |
| metallic bonds hold what together | metals |
| intermolecular bonds hold what together | molecular compounds |
| the simple cubic is the basic unit cell..what are the other 2 arrangements derived from it | body centered cubic (bcc)and face centered cubic (fcc) |
| which one packs the most atoms into the smallest space | the face centered and it is also called the "cubic close packing" |
| not all crystals have a cubic arrangement, another one that is extremely common is the | hexogonal arrangement called hexagonal close packing (hcp) |
| many metals such as titanium and magnesium have what type of structure | hexagonal close packing |
| in the body centered cubic (bcc) each atom has _____identical neighbors | 8 |
| the face centered cubic (fcc)and the hexagonal close packed (hcp) allow how many identical neighbors | 12 |
| the fcc and the hcp has about how much of its volume occupied by atoms | 74% |
| the bcc has about how much of its volume occupied by atoms | 68% |
| the simple cube has about how much of its volume occupied by atoms | 52% |
Created by:
Wrksmarter
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