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Chemistry 105 > Chap. 6: How Atoms Bond > Flashcards

Chap. 6: How Atoms Bond Flashcards

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1
Q

Electron-Dot Structures

A

A shorthand notation of the shell model of the atom, in which valence electrons (outermost electrons, but not full shells) are shown around an atomic symbol.

Can also be called Lewis Dot Structure.

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2
Q

Representative Elements

A

Representative elements fill the “s” and “p” subshells.

  • ”s” = 1 orbital
  • “p” = 3 orbitals

**Hydrogen (H) **

Group = 1A

Valence Electrons = 1

**Magnesium (M) **

Group = 2A

Valence Electrons = 2

Aluminium (Al)

Group = 3A

Valence Electrons = 3

Carbon (C)

Group = 4A

Valence Electrons = 4

Nitrogen (N)

Group = 5A

Valence Electrons = 5

Oxygen (O)

Group = 6A

Valence Electrons = 6

**Iodine (I) **

Group = 7A

Valence Electrons = 7

**Argon (Ar) **

Group = 8A

Valence Electrons = 8

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3
Q

Hydrogen (H)

Electron-Dot Structure

A
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4
Q

Magnesium (Mg)

Electron-Dot Structure

A
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5
Q

Aluminium (Al)

Electron-Dot Structure

A
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6
Q

Carbon (C)

Electron-Dot Structure

A
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7
Q

Nitrogen (N)

Electron-Dot Structure

A
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8
Q

Oxygen (O)

Electron-Dot Structure

A
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9
Q

Iodine (I)

Electron-Dot Structure

A
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10
Q

Aluminium (Al)

Electron-Dot Structure

A
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11
Q

Ionic Bonds

A

A chemical bond in which there is an electric force of attraction between two oppositely charged ions.

The transfer of electrons.

Electrostatic forces hold them together.

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12
Q

Naming Compounds

A
  1. The cation is named first and keeps the element name. It is always written first in the formula.
  2. The anion has the element name as a root with the ending “—ide”
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13
Q

Naming Transition Metals and Other Metals

A

Transition metals form more than one cation.

Example:

Fe (iron) can be…

Fe3+ or Fe2+

Let’s say we add both of them to chloride…

Fe3+ + Cl- Fe2+ + Cl-

FeCl3 FeCl2

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14
Q

Naming Transition Metals and Other Metals

(Roman Numerals)

A

The Roman numerals in parenthesis are the charges for transition metals and other metals only. When naming a transition or other metal with Roman numerals, make that charge as a subscript at the end of the name.

Example:

Iron (III) Chloride = FeCl3

Iron (II) Chloride = FeCl2

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15
Q

What is the formula for aluminium and bromine?

A
  1. Write down the ions and their charges first. To find the charge of each ion, look at your Ionic Charges Periodic Table. Aluminium (Al) has a charge of +3. Bromine (Br) has a charge of -1. Therefore: Al3+ and * Br1-.*
  2. Switch the charges. Aluminum will switch charges with Bromine. Therefore: Al3+ will turn into Al1-. Br1- will turn into Br3+.
  3. Combine the elements and drop the 1, and the positive and negative signs in the charges. Turn the charges into a subscript. Therefore, your answer will be: AlBr3
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16
Q

What is the formula for barium and nitrogen?

A
  1. Write down the ions and their charges first. To find the charge of each ion, look at your Ionic Charges Periodic Table. Barium (Ba) has a charge of +2. Nitrogen (N) has a charge of -3. Therefore: Ba2+ and N3-.
  2. Switch the charges. Barium will switch charges with nitrogen. Therefore: Ba2+ will turn into Ba<em>3-</em>. N3-will turn into N2+.
  3. Combine the elements and drop the positive and negative signs in the charges. Turn the charges into a subscript. Therefore, your answer will be: Ba3N2
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17
Q

What is the formula for lead (IV) and sulfur?

A
  1. **Write down the ions and their charges first. **To find the charge of each ion, look at your Ionic Charges Periodic Table. Lead (Pb) has already been given a charge of 4. From the table, Sulfur (S) has a charge of +2. Therefore: Pb4 and S2+.
  2. Switch the charges. Lead will switch charges with sulfur. Therefore: Pb4 will turn into Pb2+. S2+ will turn into S4.
  3. Combine the elements and drop the positive and negative signs in the charges. **Turn the charges into a subscript. Divide each charge by 2. **Therefore, your answer will be: PbS2
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18
Q

What are the formulas for magnesium oxide, barium bromide, copper (II) chloride and lithium nitride?

A
  • Magnesium Oxide: Mg2+O2- = MgO
  • Barium Bromide: BaBr
  • Copper (II) Chloride: Cu2+Cl1- = CuCl2
  • Lithium Nitride: Li3N
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19
Q

Polyatomic Ions

A

Polyatomic ions are molecular groups that behave as a single unit. An ionically charged molecule.

Example:

Ammonium NH4+

Acetate CH3CO2

Nitrate NO3-

Hydroxide OH-

Bicarbonate HCO3-

Cyanide CN-

Carbonate CO32-

Sulfate SO42-

Phosphate PO43-

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20
Q

What is the formula for copper (II) phosphate?

A
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21
Q

What is the formula for sodium cyanide?

A
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22
Q

What is the formula for tin (IV) carbonate?

A
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23
Q

What is the formula for magnesium hydroxide?

A
24
Q

What is the formula for ammonium nitride?

A
25
Q

What is the formula for chromium (III) sulfate?

A
26
Q

What is the charge of chromium (Cr) in CrCl3?

A
  1. For the first element (which is a transition metal) Cr (chromium), we do not know the charge yet. That is the element we are trying to find the charge for. So, write Cr as an x.
  2. For the second element (which is a halogen) Cl3 (chlorine), has a charge of -1. There are also 3 of those chlorine molecules (from the subscript 3).
  3. We then multiply subscript 3 by the -1 charge of the chlorine element and add it to chromium (x) and solve. The answer: CrCl3 has a charge of 3.
27
Q

What is the charge of copper (Cu) in the formula Cu3PO4?

A
  1. For the first element (which is a transition metal) Cu (copper), we do not know the charge yet. That is the element we are trying to find the charge for, so we will write that as an x for now. BUT there are 3 copper elements (from the subscript 3). So, we multiply the 3 to x → 3(x) .
  2. For the second element PO4 (phosphate), we know that the charge is -3 from the chart of Polyatomic Ions.
  3. We then add copper to phosphate and solve. The answer: Copper (Cu) has a charge of 1.
28
Q

What is the charge of iron (Fe) from Fe2S3?

A
  1. For the first element (which is a transition metal) Fe2 (iron), we do not know the charge yet. That is the element we are trying to find the charge for. So, write Fe as an x. However, there are 2 of those iron elements (from the subscript 2). So, we multiply 2 to x → 2(x) .
  2. For the second element (which is a chalcogen) S3 (sulfur), has a charge of -2. There are also 3 of those sulfur molecules (from the subscript 3).
  3. We then multiply the quantity of 3 by the -2 charge in the sulfur element and add it to iron 2(x) and solve. The answer: Fe2S3 has a charge of 3.
29
Q

Writing Lewis Structures

A
  • Nonmetals sharing electrons form covalent bonds.
  • To fill these shells requires 8 electrons. This is also called the Octet Rule.
  • The goal: to achieve noble gas configuration. Noble gases are stable and have full shells.
30
Q

NASU Method

A

N → Total electrons NEEDED to fill all shells (which is 8).

A → ACTUAL number of electrons that are available.

S → SHARED electrons.

( N – A = S )

U → UNSHARED or non-bonding electrons.

( A – S = U )

* Remember: The goal is to fill the valence shell of each atom! *

31
Q

Use the NASU method for NH3

A

* To figure out how many electrons hydrogen needs, look on your Blocks Periodic Table. Nitrogen (N) is in the P block section, meaning it that it has 8 orbitals. Thereforfore, nitrogen needs 8 electrons. Hydrogen (H) is in the S block section, meaning that it has 2 orbitals. Therefore, hydrogen needs 2 electrons. *

32
Q

NH3

Lewis Dot Structure

A

Please see the “Use the NASU method for NH3” flash card to find out how this Lewis Dot Structure was composed.

33
Q

Use the NASU method for CO32–

A

* To figure out how many electrons oxygen needs, look on your Blocks Periodic Table. Oxygen (O) is in the P block section, meaning that it has 8 orbitals. Therefore, oxygen needs 8 electrons. *

34
Q

Use the NASU method for NO2-

A

* To figure out how many electrons oxygen needs, look on your Blocks Periodic Table. Oxygen (O) is in the P block section, meaning that it has 8 orbitals. Therefore, oxygen needs 8 electrons. *

35
Q

Completing the Lewis Dot Structure

A
  • There are TWO electrons per bond.
  • Shared electrons count towards EACH and every atom.
  • Distribute only ONE LONE PAIR to satisfay the Octet Rule, but the exceptions are H and He (n = 1, so only 2 electrons can be shared).
  • CONs can have double and triple bonds (C = 4 bonds, O = 2 bonds, N = 3 bonds).
  • O is generally not bonded with another O.
  • Element farthest left in center.
36
Q

Steps to Drawing Lewis Dot Structures

A

Example: CO2

  • Place carbon (C) in the center.
  • N → Add together the total electrons NEEDED to fill all shells. Because carbon (C) and oxygen (O) are in the P block (8 orbitals), they each need 8 electrons to fill their shells. Also, since there are 2 oxygens (subscript), we multiply 2 by 8. Therefore:

8 + 2(8) = 24

• A → Add together the ACTUAL number of electrons that are available. Carbon (C) has 4 valence electrons (and because it is in Group 4A on the Periodic Table). Oxygen (O) has 6 valence electrons (and because it is in Group 6A on the Periodic Table) and there are 2 oxygens (subscript). Therefore:

4 + 2(6) = 16

• S → Subtract the SHARED electrons using this formula: N – A = S.

24 – 16 = 8

( 8 / 2 electrons = 4 shared bonds )

• U → Subtract the UNSHARED electrons using this formula: A – S = U.

16 – 8 = 8

( 8 / 2 electrons = 4 unshared bonds )

You now have all of the information to draw the Lewis Dot Structure for CO2.

Remember the Octet Rule when drawing your structure: Atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell. Therefore, carbon must have eight valence electrons too.

37
Q

VSEPR Theory

A

V → Valence

S → Shell

E → Electron

P → Pair

R → Repulsion

The VSEPR Theory is a model used to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms.

  • Goal is to minimize electron pair repulsion.
  • Bonds and lone pairs must be far apart as possible.
  • Double and triple bonds count as ONE ELECTRON GROUP.
  • Lone pairs take up more space.
38
Q

Determine the central atom and the number of electron groups. How can we minimize the repulsion?

CO2

A

Central atom: Carbon (C).

Number of electron groups: 2 electron groups (2 double bonds, 0 lone pair).

How can we minimize the repulsion? Forming the atoms into a 180° linear structure.

39
Q

Determine the central atom and the number of electron groups. How can we minimize the repulsion?

CO32–

A

Central atom: Carbon (C).

Number of electron groups: 3 electron groups (1 double bonds, 2 single bonds, 0 lone pairs).

How can we minimize the repulsion? Forming the atoms into a 120° trigonal planar structure.

40
Q

Determine the central atom and the number of electron groups. How can we minimize the repulsion?

NH3

A

Central atom: Nitrogen (N).

Number of electron groups: 4 electron groups (0 double bonds, 3 single bonds, 1 lone pair).

How can we minimize the repulsion? Forming the atoms into either a 109.5° tetrahedral structure, or into a 107° trigonal planar structure.

41
Q

Covalent Bonds

A
  • There are some elements that are “electron hogs.”
  • The electrons are concentrated around one element more than the other.
  • This is an unequal sharing of electrons.
42
Q

Electronegativity

A

Which group has the element that is the most likely to attract electrons?

Group 7A, Fluorine (F)

Which period has the element that is the least likely to attract electron?

Period 1, Francium (Fr)

*Noble Gases already have full shells.

43
Q

Polar Covalent Bonds

A
  • There is a difference in electronegativity.
  • There is a small, negative charge around the most electronegative atom.
  • Polar covalent bonds have vector (has direction, magnitude).
  • This is an unequal sharing of electrons.
44
Q

Nonpolar Bonds

A
  • Nonpolar bonds happen between the same elements.
  • Same electronegativity.
  • This bond has an equal sharing of electrons.
45
Q

Three Types of Bonds

A
  1. **Ionic Bond **— Large difference in electronegativity. Electrons are transferred.
  2. Polar Covalent Bond — Small difference in electronegativity. Electrons are more concentrated around the electronegative atom.
  3. Nonpolar Covalent Bond — No difference in electronegativity. Electrons are equally shared.
46
Q

Ionic Bond

A
  • No sharing of electrons.
  • Electrons transfer from one atom to the other.
  • FULL CHARGE.
47
Q

Dipole Moments

µ

A
  • Happens in molecules.
  • If there is an uneven distribution of electrons, the molecule is said to have a dipole moment.
  • If there is an even distribution of electrons, there is no dipole moment.
  • For example: In a water molecule (right, pictured), electrons are being pulled towards oxygen (O), making a net dipole (unequal). In a carbon dioxide molecule (left, pictured), the electrons are being pulled away equally, which does not make a dipole moment.
48
Q

Dipole-Dipole Attractions

A
  • The positive end of the dipole is attracted to the negative end of a dipole.
  • This is a STRONG interaction.
  • Hydrogen bonds are dipole-dipole attractions (H2O).
  • “Like dissolves like.” This happens between two polar substances that have partial charges. Polar substances dissolve well in other polar substances. For example: alcohol in water.
49
Q

Dipole-Induced Dipole Attractions

A
  • This is a WEAK interaction.
  • “Like dissolves like.” This happens between a polar substance and a nonpolar substance. Nonpolar substances do not dissolve well into polar substances. For Example: grease in water.
  • The dipole of one molecule can distort the electron cloud of a nonpolar molecule.
  • The result is an uneven distribution of electrons.
  • This is not a permanent change.
50
Q

Induced Dipole-Induced Dipole Attractions

A
  • Also called a Van der Waals Interaction.
  • Occurs in large atoms, like xenon (Xe).
  • This is an uneven bunching of electrons to one side of the atom.
51
Q

“Like Dissolves Like”

A

An expression used to remember how some solvents work.

  • Refers to polar and nonpolar solvents and solutes.
  • POLAR substances will dissolve in POLAR substances.
  • NONPOLAR substances will dissolve in NONPOLAR substances.
  • NONPOLAR substances will not dissolve in POLAR substances.
  • Mostly C–H bonds (nonpolar).
  • Hydrocarbon is a class of compound that is found in plastic, motor oil, diesel, and gasoline.

For example:

Grease will dissolve in grease. However, grease will not dissolve in water.

52
Q

Why do we use soap to wash our dishes?

A

Soap has a polar head and a nonpolar tail that can interact with both grease and water.

The nonpolar tail interacts with the fats, because they are alike.

The polar head (which is ionic) interacts with the water.

53
Q

Ion-Dipole Attractions

A
  • This happens in a homogenous (“homo” means “same”) mixture.
  • Mixture means at least two elements, compounds, etc.
  • There is an equal mixing.
54
Q

3 Types of Compounds

A

**Ionic Compound: ** ( + ) ( – )

**Polar Compound: ** σ+ σ-

**Nonpolar Compound: ** Even

55
Q

Tetrahedral

A

A molecular geometry in which there is a central atom (located at the center) with four (“tetra”) other atoms located at the corners.

Two types:

  • Symmetrical (nonpolar, equal sharing)
  • Asymmetrical (polar, unequal sharing)
56
Q

Are pyramid (tetrahedral) and bent shapes polar or nonpolar?

A

Polar

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