Unit 4: Bonding

Question 1

Valence Shell Electron-Pair Repulsion

Answer 1

Theory that states that a molecule adopts a shape that minimizes repulsive forces between the bonding pairs

Question 2

electronegativity

Answer 2

Measures an elements ability to attract bonding electrons

A more electronegtive element will “pull” electrons more strongly in a bond

Periodic trend: increases left to right and bottom to top; F is the most electronegative element (4.0) and Fr is the lowest (0.7)

He, Ne, Ar, Rn have no values because they are not known to form any bonds under normal conditions

Question 3

polar bond

Answer 3

Convalent bond between atoms with different electronegativities - the electrons are not shared equally

Partial charges on atoms

The greater the difference in electronegativity values between the 2 elements, the more polar the bond that joins them

Question 4

hydrophilic

Answer 4

Polar substances are hydrophilic and dissolve in water

Question 5

exceptions to octet rule

Answer 5

1. H & He are stable with 2 electrons
2. B & Al are stable with 6
3. Elements from periods 3-7 (e.g. sulfur) usually have 8 but 10 or 12 are possible (e.g. SF₆)
4. Molecules with an odd number of valence electrons - 1 must remain unpaired - generally, the element with lower electronegativity

Question 6

nonpolar molecule

Answer 6

has a symmetrical distribution of charge (e.g. CCl₄)

Question 7

covalent bond

Answer 7

Describes the force holding atoms together in a molecular compound

Involves 2 atoms sharing 2 electrons

Question 8

resonance hybrid

Answer 8

resonance is a concept that indicates the electron arrangement in some molecules (like O₃ - ozone) aren’t represented by a single Lewis structure but by 2 or more

In reality, the actual molecule is a composite of the formulas drawn and is a resonance hybrid

Question 9

molecular formula

Answer 9

Chemical formula for a molecular or covalent compound

A formula that indicates the actual number of atoms present in a molecule

Question 10

tetrahedral structures

Answer 10

Contain 4 groups around the central atom

Tetrahedral

General formula: AX₄

# of Bonded Atoms: 4

# of Unshared Pairs: 0

EX: CH₄, CH₂Cl₂

Tringonal pyramid

General formula: AX₃

# of Bonded Atoms: 3

# of Unshared Pairs: 1

EX: NH₃, NH₂Cl

Tetrahedral - bent

General formula: AX₂

# of Bonded Atoms: 2

# of Unshared Pairs: 2

EX: H₂O, OF₂

Question 11

trigonal planar structures

Answer 11

Contain 3 groups around the central atom

Trigonal planar

General formula: AX₃

# of Bonded Atoms: 3

# of Unshared Pairs: 0

EX: BF₃, BH₃

Tringonal planar - bent

General formula: AX₂

# of Bonded Atoms: 2

# of Unshared Pairs: 1

EX: SO₂, NO₂

Question 12

linear structures

Answer 12

Contain 2 groups around the central atom

General formula: AX₂

of Bonded Atoms: 2

of Unshared Pairs: 0

EX: BeCl₂, CO₂, HCN

Question 13

chemical bond

Answer 13

Forces that hold atoms together in a chemcial compound

Question 14

polar molecule

Answer 14

Has an asymetrical distribution of charge

Question 15

molecular or covalent compounds

Answer 15

A compound composed of 2 or more nonmetals and existing in discrete units of atoms held together in a molecule; electrons are shared between atoms rather than transferred from one atom to another

Often soluble in CCl₄ but not water

Question 16

ionic compound

Answer 16

A compound consisting of cations and anions in proportions that give electrical neutrality (metal and nonmetal)

Held together by ionic bonds - the attraction between ions of opposite charge

Often soluble in water but not CCl₄ (carbon tetrachloride)

Question 17

nonpolar bond

Answer 17

Covalent bond between atoms with similar electronegativity - the electrons are shared equally

No charges on atoms

Question 18

ionic bond

Answer 18

When atoms have very different electronegativities, the electrons are transferred (not shared)

Complete transfer of 1 or more valence electrons

Full charges on resulting ions

Question 19

bond length

Answer 19

Distance between the nuclei in a covalent bond

The more bonds, the stronger the pull between the 2 atoms and the shorter the bond length

Question 20

paramagnetic

Answer 20

A paramagnetic electron is an upaired electron

Question 21

hydrophobic

Answer 21

Nonpolar substances are hydrophobic and do not dissolve in water

Question 22

unit cell

Answer 22

Simplest 3D representation of the overall crystal lattice

Question 23

organic compound functional groups

Answer 23

H to the right in red circle should be OH