draw the Lewis structure for the following compounds,and predict the molecular shapes.
a) water,H2O
b)Oxygen gas,O2
c)Ammonia, NH3
d)Ammonium ion,NH4
water has 2 lone pairs and 2 surrounding atoms
oxygen gas has 2 lone pairs on each atom bonded in a double bond
1 lone pair on nitrogen bonded (single) to 3 hydrogen atoms
nitrogen is bonded to 4 hydrogen atoms, and it should have a positive charge.
Sure! I can help you draw the Lewis structures for these compounds and predict their molecular shapes. Let's go step by step:
a) Water (H2O):
To draw the Lewis structure for water, we need to determine the number of valence electrons for each atom. Hydrogen (H) has 1 valence electron, and oxygen (O) has 6 valence electrons. Since there are two hydrogen atoms, we have a total of 2 + 6 = 8 valence electrons for water.
First, we connect the oxygen atom to the two hydrogen atoms using single bonds, which uses up 2 electrons. Next, we distribute the remaining 6 electrons as lone pairs around the oxygen atom. Since oxygen needs 2 more electrons to complete its octet, each hydrogen atom will share one electron with the oxygen atom, forming two additional covalent bonds.
This results in the Lewis structure for water:
H
/
O - H
The molecular shape of water is bent or V-shaped due to the presence of two lone pairs of electrons on the central oxygen atom.
b) Oxygen gas (O2):
Oxygen gas exists as a diatomic molecule (O2), which means two oxygen atoms are bonded together. Each oxygen atom has 6 valence electrons, so the total number of valence electrons for O2 is 2 * 6 = 12.
To form a bond between the two oxygen atoms, they can share two electrons. This is called a double bond. Drawing the Lewis structure for O2, we have:
O = O
The molecular shape of oxygen gas is linear since there are no lone pairs of electrons around the oxygen atoms.
c) Ammonia (NH3):
For ammonia, we have one nitrogen atom and three hydrogen atoms. Nitrogen has 5 valence electrons, and hydrogen has 1 valence electron each. Therefore, the total number of valence electrons for NH3 is 5 + (3 * 1) = 8.
To draw the Lewis structure for ammonia, we connect the nitrogen atom to the three hydrogen atoms using single bonds. This uses up 3 electrons. Next, we distribute the remaining 5 electrons as lone pairs around the nitrogen atom.
The Lewis structure for ammonia is:
H
/
H - N - H
The molecular shape of ammonia is a trigonal pyramidal due to the presence of one lone pair of electrons on the central nitrogen atom.
d) Ammonium ion (NH4+):
The ammonium ion has the same composition as ammonia but with an extra hydrogen atom and an overall positive charge (+1). Therefore, we have one nitrogen atom and four hydrogen atoms. We need to consider the charge when determining the total number of valence electrons.
Nitrogen has 5 valence electrons, and each hydrogen atom contributes 1 valence electron. The positive charge means that one electron has been lost. So, the total number of valence electrons for NH4+ is 5 + (4 * 1) - 1 = 8.
To draw the Lewis structure for the ammonium ion, we connect the nitrogen atom to the four hydrogen atoms using single bonds, which uses up 4 electrons. Next, we distribute the remaining 4 electrons as lone pairs around the nitrogen atom to satisfy its octet.
The Lewis structure for the ammonium ion is:
H
/
H - N - H
\
H
The molecular shape of the ammonium ion is tetrahedral due to the presence of four surrounding atoms around the central nitrogen atom.
Remember, in molecular shapes, the presence of lone pairs of electrons affects the geometry around the central atom.