EL.5 Flashcards
Covalent bonding and shapes of molecules
Why do elements that are not noble gases form compounds?
They try to reach stability by gaining or losing electrons so that they have a full outer shell like noble gases do.
How are compounds formed between non metallic elements?
Electrons are shared between the atoms so they both reach stability.
What is the sharing of electrons known as?
Covalent bonding.
What are unpaired electrons in an atom when it is not in a compound?
Electrons in the outer shell that are not paired up with another electron in their orbital.
What are paired electrons in an atom when it is not in a compound?
Electrons in the outer shell that are paired up with another electron in their orbital.
When atoms join by covalent bonding, what are the electron pairs called that form the bonds?
Bonding pairs.
What are the electron pairs that are not involved in the bonding called?
Lone/non bonding pairs.
How many pairs of electrons are shared across a single covalent bond?
One.
How many pairs of electrons are shared across a double bond?
Two.
How many pairs of electrons are shared across a triple bond?
Three.
What is a dative covalent bond?
When a pair of bonding electrons both come from one of the atoms rather than each atom contributing one electron to form a bonding pair.
How is a dative covalent bond represented/indicated?
An arrow pointing from the atom donating the electrons to the atom accepting them.
How is the strength of the intermolecular attractions between covalently bonded molecules and what does it mean for its melting and boiling points?
Intermolecular forces between covalent molecules are weak, which means that it requires little energy to separate molecules from each other, this means they tend to have low melting and boiling points.
Do covalent molecules conduct electricity and why?
Covalent molecules do not conduct electricity because there are no charge particles.
What is the electron pair repulsion theory and what does it say?
It’s a theory we use to determine the specific shapes covalent molecules have as a result of bonding pairs repelling. It is the idea that the negatively charged bonding pairs would repel to be as far apart as possible giving the molecule a particular shape in space.
What shape does methane, CH4 have?
Tetrahedral.
What is the bond angle for a tetrahedral molecule?
109.5
What is the description for a tetrahedral molecule’s repulsion theory?
Four bonding pairs repel to be as far apart as possible, which gives a tetrahedral molecule with bond angle of 109.5.
In a 3D diagram, what does a solid line show?
A bond that lies in plain with the paper.
In a 3D diagram, what does a wedged line show?
A bond that is coming out of the plain/coming towards you.
In a 3D diagram, what does a dashed line show?
A bond that is going into the plain/going away from you.
What shape does ammonia, NH3 have?
Pyramidal.
What is the bond angle for a pyramidal molecule?
107
What is the description for a pyramidal molecule’s repulsion theory?
Three bonding pairs and one lone pair repel to be as far apart as possible, which gives a pyramidal molecule with bond angle of 107.
What shape does water, H2O have?
Bent.
What is the bond angle for a bent molecule?
104.5
What is the description for a bent molecule’s repulsion theory?
Two bonding pairs and two lone paris repel to be as far apart as possible, which gives a bent molecule with bond angle of 104.5.
What causes the slight change in bond angles for these shapes?
The numbers of lone pairs present, as lone pairs repel stronger than bonding pairs, approximately by 2.5 degrees per pair.
What is the bond angle for a linear molecule?
180
How many groups of electrons are there around the central atom in a linear molecule?
2
What is the bond angle for a trigonal planar molecule?
120
How many groups of electrons are there around the central atom in a trigonal planar molecule?
3
What are the bond angles for a trigonal bipyramidal molecule?
90 and 120, depending on the positions within the molecule.
How many groups of electrons are there around the central atom in a trigonal bipyramidal molecule?
5
What is the bond angle for an octahedral molecule?
90
How many groups of electrons are there around the central atom in an octahedral molecule?
6
