Matters And Materials Flashcards

1
Q

Define Valency

A

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.

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2
Q

What’s a Lewis diagram?

A

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.

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3
Q

What is a molecule?

A

It is a combination of two or more atoms that are bonded strongly enough to form a separate unit with its own distinct properties.

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4
Q

What is bond length?

A

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.

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5
Q

What is a lone pair?

A

These are electrons found in the outermost energy level of an atom and do not take any part in the bonding process.

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6
Q

What is a covalent bond?

A

A chemical bond that involves sharing a pair of electrons between atoms in a molecule.

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7
Q

What is a multiple bond?

A

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.

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8
Q

What is a dative covalent bond?

A

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.

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9
Q

Electronegativity is…

A

The measure of the amount of attraction that the atom is able to exert upon a shared electron pair within a chemical bond.

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10
Q

What two factors contribute toward electronegativity?

A

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.

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11
Q

How does comparing electronegativity help us understand molecular formation?

A

It allows us to predict whether or not a molecule will be polar or not.

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12
Q

Describe the following polarity strength:

0

A

Non polar.

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13
Q

Describe the following polarity strength:

0.1-0.89

A

Weakly polar

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14
Q

Describe the following polarity strength:

0.9-2.0

A

Polar covalent

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15
Q

Describe the following polarity strength:

2.1<=

A

Ionic

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16
Q

What is VSEPR?

A

Valence shell electron pair repulsion. Intramolecular forces or steric stresses within in a molecule.

17
Q

Arrange these from strongest to weakest.
Lone pair. Bonding pair repulsion.
Bonding pair: Bonding pair repulsion.
Lone pair: Lone pair repulsion.

A

Intermediary.
Weakest.
Strongest.

18
Q

Name the 5 molecular shapes.

A
Linear.
Angular.
Pyramidal.
Trigonal Planar.
 Tetrahedral.
19
Q

What is bond energy?

A

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.

20
Q

What is bond strength?

A

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.

21
Q

How does polarity affect bond strength?

A

The higher the polarity, the stronger the bond strength.

22
Q

What is activation energy?

A

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.

23
Q

What is the equation to determine if a reaction is exoteric or endothermic?

A

△H= E products - E reactants

If △H is negative then the reaction is exothermic. If its positive its endothermic.

24
Q

What is an intra molecular force?

A

Forces that occur within a particle.

25
Q

What is an intermolecular force?

A

Forces that occur between molecules.

26
Q

What is a Van Der Waals force?

A

Relatively weak intermolecular forces that are overall electrically neutral. They arise due to proximity. These forces of attraction are extend in all directions. They are not bonds.

27
Q

What is a London force?

A

Momentarily induced Dipole.

28
Q

What is a Keesom force?

A

Dipole-Dipole

29
Q

What other force is there besides London and Keesom?

A

Ion-Dipole

30
Q

What is the hydrogen bonding intermolecular force?

A

When a hydrogen atom bonds with a small atom of high electronegativity. A polar molecule is formed that has a relatively large sigma+ sigma- charge associated with it.

31
Q

Which gases permit hydrogen intermolecular bonding forces?

A

Nitrogen
Oxygen
Fluorine

32
Q

What attributes does the hbif add to a substance?

A

Higher intermolecular forces mean higher melting and boiling points.

33
Q

Describe NaCl’s dissolution in water.

A

The sigma- part of the H2O molecule will surround the positive part of the NaCl ion and visa versa, overcoming the ionic force bonding the Na to the Cl.

34
Q

What is a covalent bond?

A

When two non-metal atoms are able to share electrons through a process of orbital overlap when their outermost energy levels combine forming bonding pairs of electrons to form a covalent compound or molecule.

35
Q

What is an ionic bond?

A

This is when two atoms, one metal and the other a non-metal are able to bond through the process of electron transfer from the metal to the non-metal atom to form an ionic compound.

36
Q

Metallic Bonding?

A

This is when a crystal lattice of metal atoms are found where atoms are embedded in a sea of delocalised electrons formed due to the overlapping of the outermost orbitals of the metal atoms which allow for electrons to move easily through the lattice structure.