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Flashcards in Shapes of Molecules Deck (28):
1

How are molecules formed?

Atoms joined by covalent bond

2

What determines the shape of a molecule?

Arrangement in space of the atoms

3

What is the Electron Pair Repulsion Theory

It explains shapes of simple molecules with atoms bonded to a central atom. According to this theory,
-electron pairs in the valence shell of the central atoms repel eachother as far apart as geometrically possible
-lone pairs have a greater repelling effect than bonding pairs

4

If the central atom is in group 2, what shape will the molecule be and what will be the bond angle?

Linear, 180 degrees

5

If the central atom is in group 3, what shape will the molecule be and what will be the bond angle?

Trigonal planar, 120 degrees

6

If the central atom is in group 4, what shape will the molecule be and what will be the bond angle?

Tetrahedral, 109.5 degrees

7

If the central atom is in group 5, what shape will the molecule be and what will be the bond angle?

Pyramidal, 107 degrees

8

If the central atom is in group 6, what shape will the molecule be and what will be the bond angle?

V-shaped, 104.5 degrees

9

Which has the greatest repulsion between bonding pairs?

Lone pair : Lone Pair
Lone pair : Bond pair
Bond pair : Bond pair

10

Why when the central tom is in group 5, is the bond angle 107 degrees?

It has four bond pairs which gives it the tetrahedral arrangement, but due to the strong repulsion of the lone pairs, they bond pairs are pushed close together creating a bond angle of 107 degrees

11

How can a molecule have polar bonds but be a non-polar molecule?

Occurs when a molecule has a high degree of symmetry and geometric centre

12

If a molecule has a high degree of symmetry, what does this mean?

The molecule is non polar

13

What are the symmetrical molecules?

Linear, Trigonal, Tetrahedral

14

Which atom is partially negative?

Greater electronegativity

15

Which atom is partially positive?

Lesser electronegativity

16

How is a molecule symmetrical?

Example, Centre of negative charge in the central atom coincides with the geometric centre of positive charge, caused by the surrounding atoms.

17

How is a molecule not symmetrical?

Centres of positive and negative charge do not coincide. Negative charge of central atom is at the apex and the centre of positive charge is seperated

18

What is intramolecular bonding?

Bonding within the molecule that holds the atom together

19

What is intermolecular bonding?

Forces/bonding between molecules

20

What is hydrogen bonding?

a special type of dipole-dipole interaction, which occurs when hydrogen is bonded to small, highly electronegative atoms such as O, N or F

21

Hydrogen bonding in water

Highly polar due to electronegativity difference
Partial negative has strong attraction for partial positive

22

What do strong intermolecular forces mean?

It means high boiling point

23

Hydrogen sulfide has a electronegativity difference of 0.4, what does this mean

It means it is weakly polar. The partial negative charge is more diffuse and less effective on large sulphur atom than on oxygen atom

24

How does the boiling point usually increase?

It increases as the relative molecular mass increases

25

What occurs in hydrogen bonding?

Hydrogen bonds to a small, highly electronegative atom which means the share of electrons is going to be small. It readily attracts too another electronegative atom

26

Since the hydrogen atom is small, what does this mean?

Two atoms can bond to it, hydrogen bond and other by covalent bond

27

What is dipole-dipole interactions?

Negative end of one dipole is attracted to the positive end of another

28

Why are dipoles permanent?

Due to their polarity