Matters And Materials Flashcards
(36 cards)
Define Valency
The number of electrons an atom must either lose or again to achieve a filled outermost energy level and hence attain its most suitable energy state. The valency is also equal to the bond number- the number of bonds an atom is able to make when it combines with other atoms.
What’s a Lewis diagram?
The Lewis diagram is used to represent the total number of valence electrons associated with each individual atom. These diagrams use a system of dots and or crosses to represent the valence electrons.
What is a molecule?
It is a combination of two or more atoms that are bonded strongly enough to form a separate unit with its own distinct properties.
What is bond length?
This is the distance between the nuclei of the two atoms where the lowest energy and greatest stability is obtained between the atom thus forming a chemical bond.
What is a lone pair?
These are electrons found in the outermost energy level of an atom and do not take any part in the bonding process.
What is a covalent bond?
A chemical bond that involves sharing a pair of electrons between atoms in a molecule.
What is a multiple bond?
A multiple bond is made up of two or more bonds between the atoms in a molecule as a result of two or more unpaired electrons.
What is a dative covalent bond?
This is a covalent bond that is formed but the overlapping of a filled orbital containing a lone pair with the empty or vacant orbital of another atom or ion. The lone pair of electrons are equally shared within the covalent bond.
Electronegativity is…
The measure of the amount of attraction that the atom is able to exert upon a shared electron pair within a chemical bond.
What two factors contribute toward electronegativity?
The charge of the nucleus: The greater the positive charge of the nucleus, the greater the force it exerts on the electrons hence the greater the electronegativity.
The size of the atom: The smaller the atom, the greater the attraction on a shared electron pair with a bond, hence the greater the electronegativity.
How does comparing electronegativity help us understand molecular formation?
It allows us to predict whether or not a molecule will be polar or not.
Describe the following polarity strength:
0
Non polar.
Describe the following polarity strength:
0.1-0.89
Weakly polar
Describe the following polarity strength:
0.9-2.0
Polar covalent
Describe the following polarity strength:
2.1<=
Ionic
What is VSEPR?
Valence shell electron pair repulsion. Intramolecular forces or steric stresses within in a molecule.
Arrange these from strongest to weakest.
Lone pair. Bonding pair repulsion.
Bonding pair: Bonding pair repulsion.
Lone pair: Lone pair repulsion.
Intermediary.
Weakest.
Strongest.
Name the 5 molecular shapes.
Linear. Angular. Pyramidal. Trigonal Planar. Tetrahedral.
What is bond energy?
The amount of energy that must be transferred to a system in order to break the chemical bond between two atoms. The energy is measured in kilojoules.
What is bond strength?
The measure of the specific amok out of energy that must be absorbed in order to break a particular type of chemical bond in that molecule.
How does polarity affect bond strength?
The higher the polarity, the stronger the bond strength.
What is activation energy?
This is the amount of energy a system needs to absorb from its surroundings or introduced into a system before a successful reaction can begin.
What is the equation to determine if a reaction is exoteric or endothermic?
△H= E products - E reactants
If △H is negative then the reaction is exothermic. If its positive its endothermic.
What is an intra molecular force?
Forces that occur within a particle.
