chemical bonding Flashcards Preview

LC Chemistry > chemical bonding > Flashcards

Flashcards in chemical bonding Deck (93)
Loading flashcards...
1

compound

substance that is made up of two or more DIFFERENT elements combined together chemically

2

octet rule

when bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost shell

3

an ion

a charged atom or group of atoms

4

an ionic bond

the force of attraction between oppositely charged ions in a compound

5

transition metal

one that forms at least one ion with a partially filled sublevel

6

molecule

group of atoms joined together. It is the smaller particle of an element or compound that can exist independently

7

valency of an element

defined as the number of atoms of hydrogen or any other monovalent element with which each atom of the element combines

8

electronegativity

a measure of the relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond

9

electronegativity differences

-difference > 1.7 indicates ionic bonding in a compound
-difference ≤ 1.7 indicates covalent bonding in a compound

10

the value of electronegativity

-decreases down groups in Periodic Table. (Bc of increasing atomic radius, screening effect of inner electrons)

-increases across table (bc of increasing nuclear charge, decreasing atomic radius)

11

the most electronegative element

F

12

halogens

decrease in reducing power down group due to drop in electronegativity values

13

noble gases

-have 8 electrons on their outer shell + are quite stable
-generally unreactive

14

uses of noble gases

helium
argon

15

helium

used in airships as it is lighter than air
not as light as hydrogen (twice as heavy per volume) but does not burn

16

argon

most common noble gas
used to fill normal light bulbs to stop them imploding

17

limitations of the octet rule

hydrogen
lithium
transition metals

18

valency

the number of bonds an atom makes when it reacts

19

how to get valency

-can be worked out calculating the number of electrons an atom needs to lose/gain to have 8e⁻ on outer shell

-can be predicted from periodic table

20

examples of valency numbers

ammonia (contains only nitrogen and hydrogen)
methane (contains only carbon and hydrogen)
calcium bromide
silicon fluroide

21

transition metals (info)

-transition elements have variable valency
-form coloured compounds
-used as catalysts
-exceptions: zinc (Zn), scandium (Sc)

22

ionic bonding

-transfer of electrons
-ions are formed
-ionic bonding usually between Groups I and II (metals)
and groups VI and VII (non-metals)

23

cation

positive (+)

24

anion

negative (-)

25

crystal lattice

ionic substances usually form a structure called a crystal lattice

26

eg of crystal lattice

NaCl

27

why ionic substances form crystals

ionic substances form crystals bc positive ions attract negative ions in all directions

28

what shape do crystals form?

a lattice structure

29

characteristics of ionic substances

-strong forces between ions -> v. hard to break up the lattice structure
-high melting + boiling points
-usually solid at room temp
-cannot conduct electricity when solid (ions not free -> move and carry electricity)
-most dissolve in water (when dissolved, ions can conduct electricity)

30

examples of everyday ionic substances

-table salt (sodium chloride NaCl)
-fluoridation in water to prevent tooth decay (sodium fluoride NaF)