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1

intermolecular forces

attractive (repulsive) forces between molecules

2

intramolecular forces

attractive (repulsive) forces within a molecule

3

Van der Waals forces

weak attractive forces between molecules resulting from the formation of temporary dipoles

4

Dipole-Dipole

Dipole-Dipole forces are forces of attraction between the negative pole of one molecule and the positive pole of another

5

hydrogen bonds

-particular types of dipole-dipole attractions between molecules in which hydrogen atoms are bonded to nitrogen, oxygen or fluorine

-the hydrogen atom carries a partial positive charge and is attracted to the electronegative atom in another molecule. Thus, H acts as a bridge between two electronegative atoms

6

the Law of Conservation of Mass

the total mass of the products of a chemical reaction is the same as the total mass of the reactants

7

the Law of Conservation of Matter

that in any chemical reaction, matter is neither created nor destroyed but merely changes from one form into another

8

types of shapes

linear
v-shaped
trigonal planar
trigonal pyramidal
tetrahedral

9

only bonding pairs around the central atom

electrons in the bonding pairs repel each other and want to be as far apart as possible

10

no. of bonding pairs around central atom - 2

shape of molecule - lienar

example - BeH₂ , BeCl₂

bond angle - 180°

11

no. of bonding pairs around central atom - 3

shape of molecule - trigonal planar

example - BF₃ BCl₃

bond angle - 120°

12

no. of bonding pairs around central atom - 4

shape of molecule - tetrahedral

example - CH₄

bond angle - 109.5°

13

lone pairs and bonding pairs around central atom examples

in hback

14

shapes of molecules

-molecules formed when atoms are joined together by covalent bonds
-arrangement of atoms dictates shape of molecule
-figure out arrangement using Electron Pair Repulsion Theory
-Look at the bonding pairs or lone pairs around central atoms

15

lone pairs and bonding pairs around central atom

-lone pairs of electrons closer to nucleus of atom (nuclear charge sucks them in)
-bc of this they are closer together (create strong negative charge)
-their collective nuclear charge pushes bonding pairs further apart
-decreases the bond angle + distorts shape of molecule

16

polarity

-atoms in covalent bonds share electrons

-we figure it out by looking at electronegativity

17

non-polar

when atoms in a covalent bond share electrons equally, bond is said to be non-polar

Eg. H₂ , N₂ , O₂

18

polar

when electrons are shared unequally, bond is polar

eg. HCl, NH₄

19

electronegativity

-the greater the electronegativity, greater the pull on electrons
-to work it out use electronegativity table
-atom w/ greater pull on electrons becomes slightly negative while other atom in bond becomes slightly positive

20

use of electronegativity

can be used to predict nature of a bond

21

everyday life: polar

water (good solvent for ionic and polar substances)

ethanol (used in alcoholic beverages)

22

everyday life: non-polar

tetrachloroethene (used in dry cleaning)

propanone (also called acetone) (used in nail varnish remover)

23

polar molecule can be non-polar overall if it has these shapes

linear
trigonal planar
tetrahedral

ie shapes with no lone pairs

24

eg of polar molecules that is non-polar overall

BeH₂
BF₃
CH₄

25

molecules that are not symmetrical (has one lone pair) are one of these shapes

trigonal pyramidal
v-shaped

26

eg of non-symmetrical molecules

NH₃
H₂

27

polar bonds and shapes

some molecules, even tho they have polar bonds, doesn't mean they are polar molecules due to their shapes

(shape is symmetrical as there are no lone pairs of electrons)

eg. carbon dioxide, chloroform, boron trichloride

28

intermolecular bonding

between molecules

eg. between water molecules

29

intramolecular bonding

within the molecule

eg. an oxygen atom and a hydrogen atom in a molecule

30

3 types of intermolecular bonding

Van der Waals
Dipole-Dipole
Hydrogen Bonding