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LC Chemistry > Chapter 5 - Chemical Bonding > Flashcards

Chapter 5 - Chemical Bonding Flashcards

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1
Q

Compound

A

Substance made up of two or more different elements combined together chemically

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2
Q

Octet rule

A

When bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost energy level

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3
Q

What are some exceptions to the octet rule?

A

Transition metals don’t always need eight in the outer shell

Elements near helium in the periodic table tend to only have two in the outer shell

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4
Q

Ion

A

Charged atom or group of atoms which formed either by losing or gaining electrons

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5
Q

Anion

A

negative ion

has gained electron

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6
Q

cation

A

positive ion

has lost electron

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7
Q

Ionic bond

A

Force of attraction between oppositely charged ions in a compound. Ionic bonds are always formed by the complete transfer of electrons from one atom to another

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8
Q

The 3D arrangement of ions is called a …

A

… crystal lattice

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9
Q

Give examples of uses of ionic compounds

A 
Athletes take salt tablets to replace the salt lost by sweating
Washing soda (Na₂CO₃) is used to soften water
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10
Q

Valency

A

The number of hydrogen atoms (or any other monovalent element) with which each atom of the element combines

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11
Q

What are the valencies of iron?

A

Fe⁺²

Fe⁺³

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12
Q

What are the valencies of copper?

A

Cu⁺

Cu⁺²

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13
Q

What are the valencies of chromium?

A

Cr⁺³

Cr⁺⁶

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14
Q

What are the valencies of manganese?

A

Mn⁺²
Mn⁺⁴
Mn⁺⁷

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15
Q

Why do some transition metals have variable valencies?

A

There is such a small energy difference between 4s and 3d sublevels

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16
Q

What characteristics do transition elements typically show that scandium and zinc don’t?

A

Variable valency
Transition elements usually form coloured compounds
Transition elements are used as catalysts

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17
Q

Transition metal

A

One that forms at least one ion with a partially filled d sublevel

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18
Q

Molecule

A

Group of atoms joined together. It is the smallest particle of an element or compound that can exist independently

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19
Q

Sigma bond

A

Formed by the head on overlap of two s or p orbitals

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20
Q

Pi bond

A

Formed by the sideways overlap of p orbitals

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21
Q

Which is stronger: sigma or pi bond?

A

Sigma as there is an orbital overlap

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22
Q

What are the characteristics of ionic bonds?

A

Hard and brittle
High melting and boiling points
Solid at room temperature
Conduct electricity in molten state or dissolved in water

23
Q

What are the characteristics of covalent bonds?

A

Usually soft
Low melting and boiling point
Liquids, gases or soft solids at room temperature
Do not conduct electricity

24
Q

What does the VSEPR in VSEPR theory stand for?

A

Valence Shell Electron Pair Repulsion theory

25
Q

Bond pair

A

Pair of electrons that make up a covalent bond

26
Q

Lone pair

A

Other electrons present that are not involved in bonding

27
Q

Order the amount of repulsion between pairs of electrons in an atom

A

lone pair/lone pair > lone pair/bond pair > bond pair/bond pair

28
Q

What shape is this molecule? 2 bond pairs, 0 lone pairs. What size are the angles formed?

A

linear

180°

29
Q

What shape is this molecule? 3 bond pairs, 0 lone pairs. What size are the angles formed?

A

triangular planar

120°

30
Q

What shape is this molecule? 4 bond pairs, 0 lone pairs. What size are the angles formed?

A

tetrahedral

109.5°

31
Q

What shape is this molecule? 3 bond pairs, 1 lone pairs. What size are the angles formed?

A

pyramidal

107°

32
Q

What shape is this molecule? 2 bond pairs, 2 lone pairs. What size are the angles formed?

A

v-shaped

104.5°

33
Q

Electronegativity

A

The relative attraction that an atom in a molecule has for its shared pair of electrons in a covalent bond

34
Q

What are some of the uses of electronegativity values?

A
  1. Predict which compounds are ionic and covalent

2. Predict the polarity of covalent molecules

35
Q

If the difference in electronegativity values is greater than 1.7, then the compound is …

A

… ionic !

36
Q

If the difference in electronegativity values is ~ 1.2 then the compound is …

A

.. highly polar covalent

37
Q

If the difference in electronegativity values is ~ 0.9 then the compound is …

A

…. polar covalent

38
Q

If the difference in electronegativity values is ~ 0.4 then the compound is …

A

… slightly polar covalent

39
Q

If the difference in electronegativity values is ~ 0 then the compound is …

A

… non polar / pure covalent

40
Q

Polar covalent bond

A

A bond in which there is unequal sharing of the pair (or pairs) of electrons. This causes one end of the bond to be slightly positive (δ⁺) and the other end to be slightly negative (δ⁻)

41
Q

Why are there some molecules that have polar bonds but overall the molecule is non-polar?

A

This occurs when the central atom is positively charged and the negatively charges outside atoms cancel each other out due to symmetry

42
Q

How might you show polarity experimentally?

A
  1. Allow liquid to flow from a burette
  2. Put a charged rod near the liquid
  3. If the liquid is moved by the rod it is polar (molecule has a charge)
  4. If the liquid is not deflected then it is non polar
43
Q

What is the solubility rule?

A

like dissolves in like

44
Q

Intramolecular bonding

A

Bonding that takes place within a molecule, i.e it holds the atoms together (ionic and covalent)

45
Q

Intermolecular bonding

A

Forces of attraction that exist between molucules:

  • Van der Waal
  • Dipole-dipole
  • Hydrogen bonding
46
Q

Van der Waal forces

A

Weak attractive forces between molecules resulting from the formation of temporary dipoles. They are the only forces of attraction between non-polar molecules

47
Q

How do Van der Waal forces form?

A

Temporary internal shift of electrons in a molecule lead to formation of temporary dipoles and small attractive forces

48
Q

Dipole-dipole forces

A

Attractive forces between the negative pole of one polar molecule and the positive pole of another polar molecule

49
Q

Hydrogen bonds

A

Particular types of dipole-dipole attractions between molecules in which hydrogen atoms are bonded to nitrogen, oxygen or fluorine.
The hydrogen atom carries a partial positive charge and is attracted to the electronegative atom in the other molecule.
Thus, the hydrogen bond acts as a bridge between two electronegative atoms in separate molecules

50
Q

What is the range of boiling points for ionic compounds?

A

> 700°C

51
Q

What is the range of boiling points for covalent compounds?

A

<700°C

52
Q

What is the melting point of pure benzoic acid?

A

122.4°C

53
Q

A pure substance melts…

A

sharply

54
Q

An impure substance melts…

A

over a range of temps (e.g impure benzoic acid 114 - 118°C)

LC Chemistry (24 decks)

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