Higher Chemistry Flashcards
Bonding in the first 20 elements
From elements 1-20, state the elements that contain metallic bonding. (7)
Lithium, beryllium, sodium, magnesium, aluminium, potassium, calcium (Li, Be, Na, Mg, Al, K, Ca).
From elements 1-20, state the elements that contain covalent molecular bonding. (7)
Hydrogen, nitrogen, oxygen, fluorine, chlorine, phosphorus, sulfur (H2, N2, O2, F2, Cl2, P4, S8). Also all the diatomic elements.
From elements 1-20, state the elements that contain a covalent network structure. (3)
Boron, carbon diamond and silicon (B, C, S)
State all the diatomic elements. (7)
Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine.
From elements 1-20, state the elements that exists as a monatomic structure.
Helium, neon, argon (He, Ne, Ar). All the Noble Gases.
State the two common structures of carbon.
(1) carbon diamond - covalent network (2) carbon graphite - covalent layers with delocalised electrons
In higher Chemistry there is a third structure of carbon, what is it called.
carbon fullerene - covalent molecular spheres.
What is a metallic bond?
Metal atoms have low electronegativity values and they lose electrons easily. When the atoms lose electrons it becomes a positively charged ion. These positive metal ions are surrounded by the negative delocalised electrons. Its the electrostatic force of attraction between the positive metal ions and the negative delocalised electrons that keeps the metallic lattice tightly bonded together.
What is a covalent bond?
Covalent bonds are seen in covalent molecular structures and covalent network structures.
Covalent bonding only involves non metals. It involves the sharing of electrons. They share electrons as they want to have a stable electron arrangement. The electrostatic force of attraction between the positive nucleus and the negative shared electrons keeps the bond tightly bonded together.
What is an ionic bond?
An ionic bond involves the complete transfer of electrons as the atoms want to achieve a full stable electron arrangement and to do this they will either lose or gain electrons. One atom will become positively charged and the other will become negatively charged. It is the electrostatic force of attraction that keeps the ionic lattice tightly bonded together.
What is a pure covalent bond?
This happens when both atoms in the bond have the same electronegativity and the electrons will be shared equally.
e.g. H-H, F-F
What is a polar covalent bond?
A polar covalent bond is formed when two non atoms bond that have different electronegativity values, this means that one atom will attract the electrons more meaning this atom will become negatively charged and the other atom in the bond will be positively charged.
e.g. H-F , H-Cl, H-I
What does the term bonding continuum mean?
It means that at one end of the continuum you have pure covalent bonds where the electrons are being shared equally, with no separation of charge and at the opposite end you have ionic bonds where the electrons have been lost or gained, complete separation of charge. In the middle of the continuum you have polar covalent bonds but there is no defintive boundaries. The bigger the difference in electronegativities the more ionic character a compound will be.
Why do covalent network structures have very high melting points and boiling points?
Because when covalent network structures are melted or boiled many strong covalent bonds have to be broken.
Why do covalent molecular structures have low melting points and boiling points?
When covalent molecular structures are melted or boiled the weak intermolecular forces are broken, not the strong covalent bonds.
