Simple Molecular Substances (pg 116) Flashcards
What is simple molecular substances?
they are made up of molecules containing a few atoms joined together by covalent bonds
Give example of simple molecular substances for Hydrogen H2)
common ones you need to learn
Hydrogen H2, atoms have just one electron. They only need one more to complete the first shell. so they often form single covalent bonds, either with other hydrogen atoms or with other elements, to achieve this. (see diagram on page 116)
Give an example of simple molecular substances for Chlorine, Cl2)
(common ones you need to know)
Each chlorine atom needs just one more electron to complete the outer shell. so two chlorine atoms can share one pair of electrons and form a single convalent bond (see dot and cross diagram on page 116)
Give an example of a simple molecular substance for Oxygen O2)?
(common ones you need to know)
Each oxygen atom needs two more electrons to complete its outer shell, so in oxygen gas, two oxygen atoms share two pairs of electrons with each other making a couble covalent bond. (see dot and cross diagram page 116)
Give an example of a simple molecular substance for Nitrogen (N2)?
(common ones you need to know)
Nitrogen atoms need three more electrons, so two nitrogen atoms share three pairs of electrons to fill their outer shells. This creates a triple bond. (see dot and cross diagram on page 116)
Give an example of a simple molecular substances for Methane, CH4)
(common ones you need to know)
Methane, CH4, Carbon has four outer electrons. which is half a full shell. It can for four covalent bonds with hydrogen atoms to fill up its outer shell (see dot and cross diagram on page 116)
(remember you must know how to draw the diagram and dot and crosses in correct places)
Give an example of simple molecular substances for Water, H20)?
(common ones you need to know)
In water molecules, the oxygen shares a pair of electrons with two H atoms to form two single covalent bonds (see dot and cross diagram on page 116 - remember to learn how to draw the diagram with dots and crosses in correct place)
Give an example of a simple molecular substance for Hydrogen Chloride, HCl
(common ones you need to know)
This is very similar to H2 and Cl2. Again, both atoms only need one more electron to complete their outer shells (see dot and cross diagram on page 116, and remember to learn how to draw this, with the dots and crosses in the correct place)
draw a dot and cross diagram for ammonia NH3)?
see page 115 for dot and cross diagram)
Do substances containing convelent bonds usually have simple or complicated molecular structures?
simple
How are the atoms within the molecules held together with simple molecular substances?
the atoms within the molecules are held together by very strong covalent bonds. By contrast, the forces of attraction between these molecules are very weak (the lines inbetween are very weak)
Are the boiling points for simple molecular substances high or low, and why?
the melting points are very low, because the molecules are easily parted from each other.
To melt of boil a simple molecular compound, you only need to break the feeble intermolecular forces and not the covalent bonds
Most molecular substances are what, at room temperature?
gasses or liquids at room temperature
As molecules get bigger, the strengty of the inermolecular forces increases, so what is needed to break them?
as it gets bigger, the strength of the intermolecular forces increases, so more energy is needed to break them, and the melting and boiling points increase.
Do molecular compounds conduct electricity or not? and why?
They dont conduct electricity, simply because they aren’t charged, so there are no free electrons or ions.
