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CHEMISTRY-FY > S1-L7: Ionic Bonding 1 > Flashcards

S1-L7: Ionic Bonding 1 Flashcards

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1
Q

What are “chemical bonds”?

A
  • attractive forces which holds 2+ atoms together in molecule
  • ->involves valence e-‘s (most available)
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2
Q

Explain how atoms combine to gain stability

A
  • e-‘s in atoms distribute themselves in orbitals in most stable/lowest e- configuration
  • re-arranging e-‘s between atoms–> allows combined molecules to achieve even lower energy
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3
Q

What is the “Octet rule”?

A

-all elements (except Nobel gases) show tendency yo join with other elements to form compounds

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4
Q

How do elements achieve the Octet structure?

A
  • atoms tend to adjust their valence shell 8 e- by losing/gaining/sharing e-
  • ->so have same e- configuration as Nobel gas
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5
Q

To which group of elements does the Octet rule apply to?

A
  • applies to main group of elements BUT some exceptions

- ->notably transition metals using d-orbitals obey 18e- rule instead

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6
Q

Outline what forces between atoms are

A
  • attractive + repulsive forces operate between 2 atoms when they come close to each other
  • ->like charges repel (e-/e-) AND nucleus/nucleus (+)
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7
Q

How does bond length affect interaction?

A
  • refer to figure 1
  • as increases interaction energy decreases (stable) up to optimum point when distance then starts closing up and consequently interaction energy increases towards unstable point
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8
Q

Define “electronegativity”

A

-ability of atom to attract towards itself the e-‘s in a chemical bond

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9
Q

What factors affect electronegativity?-Explain where appropriate

A
  • n. of protons in nucleus
  • distance from nucleus/atom size
  • ->smaller ones able to approach nucleus more closer
  • amount of screening by inner e-‘s
  • ->i.e: n. of full shells between valence shells AND nucleus
  • covalent bond–>polarity of bonds
  • ionic bonds–>initial transfer of e-‘s
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10
Q

Which element is the most electronegative and why?

A
  • Fluorine

- ->because small AND has high nuclear charge

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11
Q

1-Electronegativity of elements: Pauling scale
2-Types of bonds
3-Electronegativity and bonding

A

1-Figure 2
2-Figure 3
3-Figure 4

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12
Q

Explain what ionic bonding is

A
  • ionic bonds formed when one or more e-‘s fully transferred between atoms
  • ionic bonding takes place between metals AND non-metals
  • non-metals try to reach + maintain noble gas structure via gaining e-‘s to form (-) ions (anions)
  • (+) and (-) ions attract via electrostatic attraction t ogive ionic bond
  • ionic bond formation involves energy decrease compared to the 2 isolated atoms
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13
Q

Formation of an Ionic Bond

A

-refer to figure 5

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14
Q

What is the significance of e- change to achieve a full outer shell

A
  • change in e-‘s must be minimum

- ->i.e: lose 2 not gain 6

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15
Q

What happens as e- are lost and gained?

A
  • gain 1 (+) charge for each e- lost
  • gain 1 (-) charge for each e- gained
  • valency of ion equals its charge
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16
Q

Define the term “isoelectronic”

A

-having same n. of e-‘s/electronic structure

17
Q

Outline the key properties of Ionic Bonds

A
  • ionic bond formed due to electrostatic attraction between (+) AND (-) charged ions
  • non-directional bond–> strength of interaction between two ions depends on distance BUT not on direction
  • ionic compounds easily dissolve + dissociate in polar solvents (i.e: water)–>bond broken–>ions separated (ion + solvent strongly attracted)
  • bonds also break when substance melted
  • ionic compound not charged overall
18
Q

What are the features of an ionic bond?

A
  • formed between metals + non-metals
  • dissolve easily in water AND other polar solvents
  • conduct electricity when molten AND in solution
  • form crystalline solids with high melting temps
19
Q

Describe the “ionic lattice” (figure 6)

A
  • every ion attracted to all other ions with opposite charge
  • ->results in repeating 3D pattern on anions (-) AND cations (+) in solid state
  • giant structure
20
Q

What is “Lattice Energy”?

A

-enthalpy of formation (energy change) of forming 1 mole of ionic solid from it’s gaseous ions
–>measures bond strength
-E.G: Na+ (g) + Cl- (g) –>NaCl (s)
(-786 kj/mol)

21
Q

How does easy cation (+) and easy anion (-) formation favour ionic bonding?

A
  • Cation (+): low ionisation energy of metal

- Anion (-): high e- affinity/ electronegativity of non-metal

22
Q

What other factors favour ionic bonding?

A
  • small size of non-metal
  • low charge on anion
  • large electronegativity difference between the combining atoms
  • high lattice energy of compound
23
Q

Define the term “polarisation”

A

-distortion of e- cloud of atom

24
Q

What is polarising power?

A

-ability to distort electron cloud of another atom

25
Q

State the factors which increase the polarising power

A
  • smaller ion + higher it’s charge

- larger atom AND more e-‘s has

26
Q

Comparison of atoms before form ions and size of ionj formed

A

-Refer to figure 7 to see comparison

27
Q

How do cations and anions compare in terms of polarisation?

A
  • cations typically smaller than anions

- ->so tend to have more polarising power while anions tend to be more polarisable (have e- cloud distorted)

28
Q

What does Fajan’s rule state about the type of character an atom has?

A
  • negative ion distorted–>covalent character

- no polarisation–> ideal ionic compound

29
Q

Describe an “Ideal Ionic Compound” (figure 8)

A
  • composes of completely separate spherical ions

- ->polarisation results in non-spherical ions AND covalent character in bond

30
Q

What does Fajan’s rule state about the covalent character an ionic compound may have?

A
  • cation small AND OR high charge–>highly polarising

- anion large AND OR high charge–>highly polarising

31
Q

Example: Why does LiCl have a low m. point and is hydrolysed by water?

A
  • Li+ small with high charge density

- Cl- large with it’s e-‘s far from nucleus

32
Q

Outline and describe “Polyatomic Ions”

A
  • Ions made up of more than one type of atom
  • bonding within polyatomic atoms covalent
  • n. of e-‘s means group has overall charge–>so able to make ionic bonds
33
Q

Common polyatomic ions

A

-Ammonium (NH4+)/ Cyanide (CN-)/ Hydroxide (OH-)/ Peroxide (O2^2-)/ Acetate (CH3CO2-)/ Oxalate (C2O4^2-)/ Nitrate (NO3-)/ Sulfate (SO4^2-)/ Carbonate (CO3^2-)/ Phosphate (PO4^3-)/ Permanganate (MnO4-)/ Dichromate (Cr2O7^2-)

34
Q

How is an ionic compound named?

A
  • first word in name cation–>usually same as parent element (except ammonium)
  • oxidation state of metal can be given after name–>like copper (II)/Iron (III)
  • second word in name is cation
  • ->if second ion polyatomic then it is just name of polyatomic ion
  • if second ion element is end of element’s name then change to -ide
  • ->e.g: Chlorine–>chloride OR oxygen–>oxide
35
Q

Outline important Cations in the body and the significance of some

A
  • Na+/K+ : signaling/ muscle contraction
  • Ca2+ : skeleton–>key role in bones
  • H+/ Mg2+
36
Q

What are some of the important Anions in the body?

A

-Cl-/ HCO3-/ HPO4 2-/ SO4 2-/ PO4 3-

37
Q

Summary of lecture

A
  • Chemical bonding: attractive AND repulsive forces between atoms
  • lowering of energy of combining atoms
  • octet rule
  • electronegativity
  • Types of chemical bond-Ionic Bond:
  • ion formation
  • ions & ionic bonds
  • ionic bonding AND periodic table
  • ionic compound properties
  • naming of ionic compounds

CHEMISTRY-FY (11 decks)

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