chemical bonding

Question 1

what are gas clouds made up of

Answer 1

a mixture of atoms and molecules together with the dust of solid material from old stars

Question 2

how are gas clouds detected

Answer 2

by radio and infrared telescopes on Earth and by spectroscopic instruments carried by rockets

Question 3

what do all noble gases have

Answer 3

a full outermost shell of electrons

Question 4

how do other elements try achieving a full stable shell of electrons

Answer 4

by losing or gaining electrons

Question 5

what does ionic bonding involve

Answer 5

metals reacting with non metals

Question 6

when are ions formed

Answer 6

if the overall energy change when metals react with non metals is favourable

Question 7

what happens in ionic bonding

Answer 7

electrons are transferred from the metal atoms to the non metal atoms giving the metal and non metal a stable electronic configuration of a noble gas

Question 8

how are the ions held

Answer 8

by electrostatic attraction between oppositely charged ions

Question 9

what do sodium and chlorine form

Answer 9

sodium chloride

Question 10

what is an ionic bond

Answer 10

the bond between oppositely charged ions that attract each other strongly

Question 11

how does a giant lattice form

Answer 11

in the solid compound each ion attracts many others of opposite charges to build up a lattice

Question 12

what ions do group 1 elements form

Answer 12

+1 ions

Question 13

what ions do group 2 elements form

Answer 13

+2 ions

Question 14

what ions do group 3 elements form

Answer 14

+3 ions

Question 15

what ions do group 6 elements form

Answer 15

-2 ions

Question 16

what ions do group 7 elements form

Answer 16

-1 ions

Question 17

write the formula for chromium (III) hydroxide

Answer 17

• identify the atoms and charges a compound is made of - chromium (III) hydroxide is made of chromium (III) ions (Cr3+) and hydroxide ions (OH-)
• work out the formulas so the charges balance - to balance the +3 charge you need 3 -1 charges
• Cr(OH)3

Question 18

why don’t non metallic elements form ions when they react

Answer 18

it isn’t energetically favourable to form ions

Question 19

what happens when non metals react

Answer 19

electrons are shared between atoms of the element

Question 20

what is covalent bonding

Answer 20

sharing of electrons

Question 21

what is the result of covalent bonding

Answer 21

the resulting compound is mroe stable than the individual elements. shared electrons count as part of the outer shell of both atoms in the bond

Question 22

what are covalent bonds

Answer 22

bonds formed by sharing electrons

Question 23

how are the two atoms held together in covalent bonding

Answer 23

the positively charged nuclei are simultaneously attracted to the negatively charged shared electrons

Question 24

what happens when electrons are shared

Answer 24

the atoms acheive more stable electrons

Question 25

what are bonding pairs

Answer 25

electron pairs which form bonds

Question 26

what are lone pairs

Answer 26

pairs of electrons not involved in bonding

Question 27

whats a double bond

Answer 27

when two pairs of electrons form a covalent bond e.g. oxygen and carbon dioxide

Question 28

whats a triple bond

Answer 28

when three pairs of electrons form a covalent bond e.g. nitrogen and hydrogen cyanide

Question 29

what are the three types of covalently bonded structures

Answer 29

- polymers - simple molecular structures - covalent network structures

Question 30

describe the bonding in carbon monoxide

Answer 30

involves a triple bond. two of the pair of electrons are formed by the carbon and oxygen atoms each contributing one electron to the pair (ordinary covalent bonds) however both electrons in the 3rd pair come from the oxygen atom (dative covalent bond)

Question 31

what is a dative covalent bond

Answer 31

both bonding electrons come from the same atom.

Question 32

how is a dative bond shown

Answer 32

by an arrow, it points away from the atom that is donating the pair of electrons

Question 33

how are the hydrogen atoms in a hydrogen molecule held together

Answer 33

their nuclei are both attracted to the shared electrons. both atoms are identical so the electrons are all shared equally

Question 34

what is the atomic core made up of

Answer 34

everything except the outer electrons

Question 35

what are the atomic cores attracted to in all atoms

Answer 35

to the shared electron pairs

Question 36

what is the charge of the atomic core of fluorine

Answer 36

Fluorine (2,7) nucleus has a charge of +9 (has 9 protons) innermost shell has a charge of -2 (2 electrons in the 1st shell) the core has a charge of 7+ (9-2=7)

Question 37

how is the F2 molecule held together

Answer 37

the 7+ core charges are attracted to the negative charges on the shared electrons.

Question 38

what is often the case with atoms bonded together

Answer 38

they're often different sizes.

Question 39

which are more attracted to the shared electrons - the smaller or bigger atom

Answer 39

the core of the smaller atom will be closer to the shared electrons and will exert a stronger pull on them.

Question 40

which atoms are also strongly attracted to the shared electrons

Answer 40

atoms with a greater core charge

Question 41

how do atoms attract bonding electrons

Answer 41

unequally

Question 42

why do atoms get a slightly positive or negative charge

Answer 42

one atom gets a slightly negative charge because it has a greater share of the bonding electrons. the other atom becomes slightly positively charged because it has lost its share in the bonding electrons

Question 43

what are slightly positive and slightly negative bonds called

Answer 43

polar bonds

Question 44

why is the O-H covalent bond polar

Answer 44

the two electrons in the bond are drawn closer to the oxygen atom athan the hydrogen atom

Question 45

what do metals and non metals form

Answer 45

ionic compounds

Question 46

what do non metals form

Answer 46

covalent compounds

Question 47

what do metals form

Answer 47

metallic compounds

Question 48

what is electronegativity

Answer 48

a measure of the ability of an atom in a molecule to attract electrons towards it. it measures an atoms attraction for bonding electrons

Question 49

an atom is highly electronegative if...

Answer 49

it has strong electron pulling powers in covalent bonds

Question 50

which atoms are more electronegative

Answer 50

if you exclude the noble gases the elements are more electronegative at the top of the group and at the RHS of the periodic table.

Question 51

what do highest electronegativities correspond with

Answer 51

reactive non metals with small atoms

Question 52

what do lowest electronegativites correspond with

Answer 52

reactive metals with large atoms

Question 53

describe polar bonds

Answer 53

they're like covalent bonds with a bit of ionic character in them. ionic and covalent bonds are extreme forms of bonding - polar bonds are in between the two.

Question 54

the bigger the difference in electronegativity between the atoms ....

Answer 54

.... the more polar the bond and the greater the ionic character

Question 55

how do metal atoms acheive a full outer electron shell

Answer 55

metal atoms lose their outer electrons to form a lattice of regularly spaced positive ions. the outer electrons contribute to a sea of delocalised electrons which move freely through the lattice of cations

Question 56

what is each positively charged ion in the metal attracted to

Answer 56

the negatively charged delocalised electrons

Question 57

what is a metallic bond

Answer 57

the electrostatic attraction between the cations and the delocalised electrons

Question 58

what does the strength of the metallic bond depend on

Answer 58

the number of electrons per atom available for delocalisation

Question 59

more electrons lost =

Answer 59

= a more stronger bond