Outcome 1: Bonding and Chemical Symbolism Flashcards
What are covalent bonds?
Shared pairs of outer electrons between non-metal elements to increase stability
Which elements form diatomic molecules?
Group 7 elements (the halogens)
Why does covalent bonding occur in the elements?
For non-metals to gain a full outer shell of electrons
When does covalent bonding occur in molecular compounds?
When more than one type of non-metal element join together to increase stability
Why are electrons shared in covalent molecular compounds?
To give a stable electron arrangement
For linear structures, what is the symmetry of a non-polar covalent molecule?
Symmetrical
For linear structures, what is the polarity of a symmetrical polar covalent molecule?
Non-polar (as it is symmetrical, the polarity cancels out)
For linear structures, what is the polarity of an unsymmetrical polar covalent molecule?
Polar (as the molecule is unsymmetrical, the polarity remains)
Permanent dipole-permanent dipole between molecules
How is polarity of a molecule affected when it is an angular structure?
Polar covalent molecules are always unsymmetrical so polarity remains.
Polar bonds always have polar molecules
What elements are required for hydrogen bonding to occur?
H- Oxygen/ Nitrogen/ Fluorine
How is polarity affected by covalent molecules in a pyramidal structure?
They are always unsymmetrical, polarity remains, if polar bonds are present the molecule is always polar
How is polarity affected by a symmetrical covalent molecule with a tetrahedral structure?
Polarity cancels out so molecule is non-polar
How is polarity affected by unsymmetrical covalent molecules with a tetrahedral structure?
Polarity remains so molecule is polar
pd-pd
What state are metals at room temperature?
Solid
Describe metallic bonding
- Atoms pull tightly together and force valence electrons away from their ‘original atom’
- valence electrons become a ‘sea of delocalised electrons’
- metal atoms become positive metal ions
- electrostatic attraction between positive metal ions and negative delocalised electrons
What are the melting/boiling points in metallic bonds?
High
Metallic bonds are strong to break because of the electrostatic attraction between positive ion and negative delocalised electrons
Conductivity in metallic bonding
Conduct due to delocalised electrons free to move around
Metallic bonding solubility in water
Insoluble
What are the names for the positive and negative ions formed in ionic bonding?
Positive ion - cation
Negative ion - anion
Describe ionic bonding
- Positive metal ions and negative non-metal ions are formed by full transfer of electrons from metal to non-metal
- Positive metal ions and negative non-metal ions formed
- Ionic bond is formed by the electrostatic attraction between positive metal ions and negative non-metal ions
- Ionic lattice structure is formed with the same ratio of metal ions to non-metal ions from the chemical formula
What are the three types of intermolecular bonding?
London dispersion forces (Weakest)
Permanent-dipole to permanent-dipole
Hydrogen bonding (Strongest)
Describe london dispersion forces
- Temporary dipoles
- Uneven distribution of electrons in atom
- Natural movement of electrons which create temporary induced dipoles
Describe permanent-dipole to permanent-dipole bonds
- Permanent dipoles
- Differences in electronegativity
- Attraction between permanent dipole of molecules
Describe hydrogen bonding
- Permanent dipole
- Between H and O/N/F
- Hydrogen bonds are between molecules
