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Bettel Plus Chang Chemistry > 4. Chemical Bonds > Flashcards

4. Chemical Bonds Flashcards

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1
Q

Gilbert Lewis (1916)

A

-lack of chemical reactivity of noble gases indicates a high degree of stability of their electron configuration (filled valence shell)

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2
Q

Octet rule

A

-When undergoing chemical reactions, atoms of Group 1A-7A tend to gain, lose or share sufficient electrons to achieve eight valence electrons

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3
Q

Anion

A

-atoms with almost eight valence electron
-tend to gain electrons ➡️ negatively charged ion

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4
Q

Cation

A

-atoms with only one or two valence electron
-tend to lose electron ➡️ positively charged ion

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5
Q

Reasons why octet rule is not perfect

A
  1. Ions of period 1 and 2 elements with charges greater than +2 are unstable. (i.e., unstable ang B+3, C+/-4)
  2. Does not apply to Group 1B-7B (transition elements). (i.e. Cu can either be Cu+1 or Cu+2)
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6
Q

Atoms and their ions are…

A

completely different chemical species and have completely different chemical and physical properties

(i.e. sodium and chlorine atoms are both poisonous. However, NaCl (sodium and chlorine ions) is a common table salt)

(i.e. F2 poisonous and corrosive gas. F- ion in the form of NaF is used for toothpastes)

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7
Q

Naming monoatomic ions

A

•Elements of Group 1A, 2A, 3A form only one type of cation
-name of metal followed by “ion”
-i.e. Na+ sodium ion

•Transition elements form more than one type of cation
-write the charge in roman numeral right after the name of metal (i.e. Cu+2 Copper (II) ion)
-no need to do this if the transition element can only form one cation (i.e. Ag+ Silver ion)

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8
Q

Naming monoatomic anions

A

-adding -ide to the stem part of the name
-i.e. F- Fluoride, O2-, Oxide

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9
Q

TWO MAJOR TYPES OF CHEMICAL BONDS
1. Ionic bond

A

-Chemical bond resulting from the attraction between a cation and anion (lose/ gain electrons)
-usually formed between metal and nonmetal

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10
Q

TWO MAJOR TYPES OF CHEMICAL BONDS
2. Covalent Bond

A

-bond resulting from sharing of electrons between two electrons
-two nonmetals or nonmetal and metalloid

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11
Q

Electronegativity

A

-measure of an atom’s attraction for the electrons it shares in a chemical bond

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12
Q

Linus Pauling (1930s)

A

-Pauling scale: most widely used scale of electronegativity
-Fluorine (most electronegative element), with a value of 4.0
-other elements are assigned values relative to fluorine

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13
Q

Electronegativity and ionization energy

A

•Ionization energy- amount of energy necessary to remove electron from an atom
•Electronegativity- how tightly an atom holds the electrons that it shares with another atom

-same trend sila; increases left to righr, bottom to top

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14
Q

Forming ionic bonds

A

-transfer of one or more valence electrons from an atom of lower electronegativity to the valence shell of an atom of higher electronegativity

-difference of electronegativity is 1.9 or greater

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15
Q

Predicting formulas of ionic compound

A

-the total number of positive charges must equal the total number of negative charges (i.e. Al+3 and S-2 ➡️ Al2S3)

-subscripts in the formulas for ionic compound represent the ratio of ions; reduce to lowest term (i.e. BaO)

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16
Q

How to name ionic compounds
1. Binary ionic compounds of metals that form only one positive ion

A

-name of the metal from which the cation was formed, followed by the name of anion (i.e. AlCl3 aluminum chloride)

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17
Q

How to name ionic compounds
2. Binary ionic compound of metals that form more than one positive ion

A

-use roman numerals in the name to show charge
-for common names, use the -ous/ -ic system
-i.e. Copper (II) oxide or cupric oxide
Copper (I) oxide or cuprous oxide

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18
Q

How to name ionic compounds
3. Ionic compounds that contain polyatomic ions

A

-name the positive ion first and then the negative ion, separate word
-i.e. (NH4)2SO3 ammonium sulfite
NaH2PO4 sodium dihydrogen phosphate

19
Q

Formation of covalent bond

A

-electron pairs are shared between two atoms
-filld the valence shell of each electron
-electronegativity difference is less than 1.9

20
Q

Nonpolar covalent bond

A

-electrons are shared equally
-difference of electronegativity: Less than 0.5

21
Q

Polar covalent bond

A

-electrons are shared unequally
-electronegativity difference 0.5-1.9
-more electronegative atom gains greater fraction of shared electrons; gains partial negative charge
-less electronegative atom gains lesser fraction of shared electrons; gains partial positive charge

22
Q

Dipole

A

-chemical species which there is a separation of charge; positive and negative poles

23
Q

Bonding electrons

A

Valence electrons involved in forming a covalent bond (shared electrons)

24
Q

Nonbonding electrons

A

Valence electrons not involved in forming covalent bonds (unshared electrons)

25
Q

Single bond

A

A bond formed by sharing one pair of electrons and represented by single line between two atoms

26
Q

Lewis structure

A

A formula for a molecule or ion showing all pairs of bonding electron as single/ double/ triple bonds and all nonbonded electrons as pair of lewis dots

27
Q

Structural formula

A

-Formula showing how atoms in a molecule or ion are bonded together
-similar to lewis structure BUT shows ONLY THE BONDING PAIRS of electrons

28
Q

Double bond

A

-sharing of two pairs of electrons represented by two lines
-most common between atoms of C, N, O, S

29
Q

Triple bond

A

-sharing of three pairs of electrons represented by three lines
-most common between atoms of C and N

30
Q

Exceptions to octet rule

A

-molecules that contain an atom with more than eight electrons in its valence shell
-atoms of period 3 elements have one 3s, three 3p, and five 3d orbitals; can accommodate more than eight electrons in their valence shell
-i.e. phosphine (8 electrons at P)
Phosphorus pentachloride (10 e)
Phosphoric acid (10 e)

31
Q

How to name binary covalent compound

A
  1. Name the less electronegative element
  2. Name the more electronegative element and add -ide
  3. Use prefixes di-, tri-, tetra- etc. Omit mono when it refers to the first atom named, and it is rarely used with second atom (except carbon monoxide)

-i.e. N2O Dinitrogen oxide

32
Q

Trivia
Dinitrogen oxide aka?

A

Nitrous oxide
Laughing gas
Hahahahahaha

33
Q

Resonance

A

-A theory that many molecules and ions are best described as hybrid of two or more Lewis contributing structures

-Linus Pauling (1930s)

34
Q

Contributing structure/ resonance structure/ resonance contributors

A

-representations of a molecule or ion that differ only in the distribution of valence electron (ibat ibang version ng lewis structure ng molecule)

35
Q

Resonance hybrid

A

-molecule or ion described as a composite or hybrid of a number of contributing structures

-interconnecting various contributing structures with double headed arrows

36
Q

Writing acceptable contributing structures

A
  1. All contributing structures must have the same number of valence electrons
  2. All contributing structures must obey the rules of covalent bonding.
    -max 2 electrons for hydrogen
    -max 8 electrons for period 2 elements
    -max 12 for period 3 elements (i.e. P,S)
  3. The positions of all nuclei must be the same in all structures (DIFFER ONLY IN VALENCE ELECTRONS DISTRIBUTION)
  4. All structures must have the same number of paired and unpaired electrons
37
Q

How to predict bond angles in covalent molecules

A

-using Valence-Shell Electron-Pair Repulsion (VSEPR) model

38
Q

Bond angle

A

The angle between two atoms bonded to a central atom

39
Q

Valence-Shell Electron-Pair Repulsion (VSEPR) model

A

-like charges repel so the various region of electron density around an atom (bonded and unshared electrons) spread out so that each is as far away as possible from the others

40
Q

Common Predicted Molecular Shapes (VSEPR model)
1. Linear

A

•Regions of density around central atom: 2
•Predicted bond angle: 180°
•Examples: CO2, Acetylene (C2H2)

41
Q

Common Predicted Molecular Shapes (VSEPR model)
2. Trigonal planar

A

•Regions of density around central atom: 3
•Predicted bond angle: 120°
•Examples: Ethylene (C2H4), Formaldehyde (CH2O)

42
Q

Common Predicted Molecular Shapes (VSEPR model)
3. Tetrahedral

A

•Regions of density around central atom: 4
•Predicted bond angle: 109.5°
•Examples: CH4, NH3, H2O

43
Q

How to determine if a molecule is polar

A
  1. It has polar bonds
  2. Its centers of partial positive charge and partial negative charge lie at different places within molecule

Bettel Plus Chang Chemistry (19 decks)

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